Hálózati kifejezések, rövidítések listája AAL ATM adaptation layer. The layer in the ATM model that provides the protocol between packet services and any ATM cell-oriented switching devices. AAL3/4 ATM adaptation layer supported by Bay Networks routers, used only for SMDS-to-ATM internetworking, and supported only over ATM data exchange interface (ATMDXI). AAL5 ATM adaptation layer supported by Bay Networks routers and used for connectionless data traffic, such as LAN protocols. AAL-SDU ATM adaptation layer service data unit. Packet of data containing information about the ATM adaptation layer, such as AAL5. AAR Automatic alternative routing. Automatic switching of a call to other routes when first choice routes are unavailable. AARP AppleTalk Address Resolution Protocol. Part of Apple Computer's AppleTalk protocol; maps AppleTalk addresses to their equivalent hardware addresses. AAUI Apple attachment unit interface. Apple Computer's version of the Ethernet AUI connector. See also AUI. ABM Asynchronous balanced mode. A service of the SNA data link level in IBM's token-passing ring that allows devices to send data link commands at any time. ABR Automatic beacon resolution. A patented process by which Bay Networks token ring agent software identifies and isolates (wraps) a beaconing station to maintain ring stability. See also beacon resolution. AC Access control. The process of permitting or denying use of the components or services of a communications network. Alternating current. AccelarTM Bay Networks product family of routing switches providing high-performance switching and routing solutions, supporting 10 mb/s, 100 mb/s, and Gigabit (1000 mb/s) Ethernet ports. access channel control The collection of logic and protocol machines managing data transfer between link stations and their media access control layers.
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Hálózati kifejezések, rövidítések listája AAL ATM adaptation layer. The layer in the ATM model that provides the protocol between packet services and any ATM cell-oriented switching devices. AAL3/4 ATM adaptation layer supported by Bay Networks routers, used only for SMDS-to-ATM internetworking, and supported only over ATM data exchange interface (ATMDXI). AAL5 ATM adaptation layer supported by Bay Networks routers and used for connectionless data traffic, such as LAN protocols. AAL-SDU ATM adaptation layer service data unit. Packet of data containing information about the ATM adaptation layer, such as AAL5. AAR Automatic alternative routing. Automatic switching of a call to other routes when first choice routes are unavailable. AARP AppleTalk Address Resolution Protocol. Part of Apple Computer's AppleTalk protocol; maps AppleTalk addresses to their equivalent hardware addresses. AAUI Apple attachment unit interface. Apple Computer's version of the Ethernet AUI connector. See also AUI. ABM Asynchronous balanced mode. A service of the SNA data link level in IBM's token-passing ring that allows devices to send data link commands at any time. ABR Automatic beacon resolution. A patented process by which Bay Networks token ring agent software identifies and isolates (wraps) a beaconing station to maintain ring stability. See also beacon resolution. AC Access control. The process of permitting or denying use of the components or services of a communications network. Alternating current. AccelarTM Bay Networks product family of routing switches providing high-performance switching and routing solutions, supporting 10 mb/s, 100 mb/s, and Gigabit (1000 mb/s) Ethernet ports. access channel control The collection of logic and protocol machines managing data transfer between link stations and their media access control layers.
Access Communications Node (ACN) Designed for both service provider and enterprise environments, the ACN product line provides support for a comprehensive set of legacy applications/protocols as well as applications based on IP networking. This comprehensive set of protocols allows network managers to continue to use legacy-based applications as theymigrate from X.25 or synchronous networks to IP and frame relay networks. access control byte In an 802.x frame, the byte following the start of the frame delimiter that determines whether it is an Ethernet, token ring, or other type of frame. Access Feeder Node (AFN®) An early Bay Networks fixed-configuration multiprotocol router/bridge with one or two LAN interfaces and two serial interfaces. Access Link Node (ALN) An early Bay Networks fixed-configuration multiprotocol router with two LAN interfaces and two serial interfaces. access method A set of rules by which network stations arbitrate their access to a shared-media LAN. Examples include ATM, Ethernet, token ring, and FDDI. Access Node (AN®) Bay Networks single Ethernet or token ring cost-effective router for connecting small remote offices. Access Node Hub (ANHTM) Bay Networks integrated hub with 8 or 12 hub ports and one router port that integrates routing services with Ethernet or token ring connectivity. access priority In a token ring network, the maximum priority a received token can have for the adapter to use it for transmission. Access Stack Node (ASNTM) Bay Networks stackable (and therefore, scalable) router hardware platform that provides a growth-oriented routing solution. accounting management One of the five network management application areas defined by ISO; includes applications to help users allocate the costs of the various network resources. See also network management, ISO. ACK ACKnowledgment. A message sent by a receiving station to acknowledge correct receipt of a transmission. See also NAK. ACL Access control list. The usual means by which access to and denial of network services is controlled by network security systems. It is a list of the available services and the hosts permitted to use each service. ACP Access Control Protocol. Bay Networks software utility that provides a wide range of security features to Annex and Remote Annex users, including password authentication, dialback, per user profiles, and access to third-party authentication systems such as Kerberos, Safeword, or SecurID.
ACSE Association control service element. An application level protocol used in OSI to establish a connection between two applications. A/C set errors. Within token ring Report Error frame conditions, errors generated by the upstream station when it is copying a frame but cannot set the Address Recognized (A) bits or Frame Copied (C) bits. ACT Absolute congestion threshold. active hub The central connecting device in a network that regenerates or amplifies transmission signals. An active hub can be used to add workstations to a network or to increase the distance between workstations and a file server. See also passive hub, intelligent hub, repeater. active monitor A single station on a token ring network that performs tasks such as token monitoring and resolving certain error conditions. See also AMP. active open The operation that a client performs to establish a TCP connection with a server at a known address. active retiming A process of constantly retiming and regenerating the token ring data at each lobe port to increase the cable distances supported. ACTLU Activate logical unit. ACTPU Activate physical unit. AD Administrative domain. A collection of hosts and routers and interconnecting network(s) managed by a single administrative authority. adapter (1) A printed circuit board that fits into a slot in a computer to enable it to perform a particular function; for example, to connect the computer to a network. See also NIC. (2) A connector that joins cables and devices that have dissimilar interface pin or signal configurations. Adaptive Networking A set of Bay Networks products and cornerstone technologies that transition today's networks to the IP-optimized networks of tomorrow. adaptive routing Routing that automatically adjusts to network changes, such as changing traffic patterns or failures. ADCCP Advanced Data Communication Control Procedures. A bit-oriented protocol developed by ANSI. See also ANSI.
address A unique identifier assigned to networks and stations that allows each device individually to receive and reply to messages. Three types of addresses are commonly used on networks: e-mail address; IP, internet, or Internet address; and hardware or MAC address. See also Class A/B/C address, IP address, MAC address. address control Defines who can transmit to specified hosts, gateways, or ports on gateways and terminal servers. Address lists are password protected and can be restricted. address field The part of a protocol data unit (PDU) that identifies one or more addressable entities. The address may be a single-source, single-destination, or multiple-destination (multicast or broadcast) address. address learning The process of adding router or bridge source addresses to a device MAC address table after a new connection has been made. Global learning is accomplished by sharing station MAC addresses between connected Ethernet networks. Local learning is dynamic learning by an individual Ethernet port of the source addresses of the frames received on that port. address pair A pair of address fields in a protocol data unit (PDU) that designates the ordered destination and source service access point (SAP) address. address tables Tables stored in switches, bridges, and routers that enable them to "remember" device physical and logical addresses. ADSL Asymmetric Digital Subscriber Line. An asymmetric transmission of data over existing twisted pair copper telephone lines, converting analog data to digital at the subscriber end. Downstream data transmission speeds (that is, to a subscriber) are greater than that of upstream data flow (that is, to a server). ADSL Forum An association of telecommunications companies providing information on ADSL technology, applications, systems, market, and trials. http://www.adsl.com/ ADSP AppleTalk DataStream Protocol. Part of the session layer (OSI reference model) of Apple Computer's networking protocol. Advanced agent An SNMP agent for a Bay Networks device that performs the functions of a Standard agent and also provides the information needed to depict concentrator configuration and link status for all attached stations in a network. Advanced agents are level 2 agents. See also Standard agent, Advanced AnalyzerTM agent. Advanced AnalyzerTM agent A high-level (level 3) software agent used in Bay Networks products that provides all functions of an Advanced agent plus full RMON statistical support. See also Advanced agent, Standard agent. Advanced Remote NodeTM (ARN) A Bay Networks BayStack access router with multiple LAN interfaces. Slots for WAN adapter modules provide WAN connectivity and facilitate remote network management.
AEP AppleTalk Echo Protocol. AFI AppleTalk Filtering Interface. AFP AppleTalk Filing Protocol. agent Intelligent software that monitors a managed SNMP network device, such as a network management module (NMM), and gathers statistical data in management information base (MIB) format. A central network management entity regularly polls the agents and downloads the contents of their MIBs. See also Advanced agent, Advanced AnalyzerTM agent, Standard agent. aging A software process that tracks how long a particular table entry remains in the table. The age of an entry (for example, a route entry in a routing table) determines whether to keep or "age-out" (delete) the old entry. aging margin A portion of the power budget of an optical fiber link that is reserved to protect against deterioration of fiber or component performance. AI Artificial intelligence. AIS Alarm indication signal (T1 lines). A signal used in the OSI reference model and also in broadband ISDN networks to indicate the presence of an alarm or error somewhere on the network. AIX Advanced Interactive Executive. An IBM management platform that is used to operate network management applications, such as the Bay Networks Optivity application. ALAP AppleTalk Link Access Protocol. The underlying protocol for packet transmission between nodes on a single Apple Computer AppleTalk network. Corresponds to the data link layer of the OSI reference model. alignment error (1) In the IEEE 802.3 specification, a received frame that contains a total number of bits not divisible by eight and fails the checksum test. This failure may be the result of a collision, a failed transceiver or controller, hardware mismatches, bad cabling, a nonfunctioning node, and similar examples. (2) On a network, the number of packets received that contain improperly aligned data. allocations (1) In broadband networks, the assignment of specific frequencies for various communications uses. (2) In digital networks, the assignment of specific amounts of bandwidth or other resources to various end users, network devices, channels, or protocols. am Amplitude modulation.
AMI Address mark inversion or alternate mark inversion (T1 lines). A signal-encoding scheme in which a "1" is represented alternately as positive and negative voltage. It does not use translation coding but can detect noise-induced errors at the hardware level. AMP Active monitor present. A signal sent by the active monitor in a token ring network to notify other stations on the ring of its presence. AN Access Node. Bay Networks single Ethernet or token ring cost-effective router for connecting small remote offices. ANHTM Access Node Hub. Bay Networks integrated hub with 8 or 12 hub ports and one router port that integrates routing services with Ethernet connectivity. ANI Automatic Number Identification. A call association type service that tells the recipient of a telephone call the telephone number of the person making the call. This number can be passed to computer equipment to automatically retrieve associated information about the caller (that is, account status, billing records, and so on). See also DNIS. AnnexTM Bay Networks servers for connecting such asynchronous devices as terminals, printers, and modems to multiprotocol Ethernet LANs. Annex ManagerTM Bay Networks Motif-based GUI that manages Annex and Remote Annex servers. (Motif is the standard graphical interface for UNIX.) ANR Automatic Network Routing. An APPN high-performance routing (HPR) option that provides connectionless end-to-end routing. It reduces storage and processing requirements for routing packets through intermediate nodes. ANSI American National Standards Institute. A private organization that accredits standards organizations and oversees standards development processes in the United States. Members include manufacturers, common carriers, and other national standards organizations such as the Institute of Electrical and Electronics Engineers (IEEE). http://web.ansi.org/default_js.htm ANSI/IEEE 802.x The complete name of IEEE 802.x standards. See also 802.x, IEEE 802, IEEE 802.3, IEEE 802.5. ANSI T1 Committee A committee sponsored by the Alliance for Telecommunications Industry Solutions (ATIS), concerned with developing standards and reports related to the interoperability of telecommunications networks. http://www.t1.org/ AO/DI Always On/Dynamic ISDN.
AOT Polled Asynchronous over TCP/IP, also Polled Asynch Protocol or Asynch Passthru over TCP. A Bay Networks router software for WANs that enables routing of asynchronous traffic polled from alarm hosts to alarm devices over a TCP/IP backbone. APE All-Paths Explorer. Frame generated by an end station configured for all-paths broadcast routing that traverses all paths between source and destination end stations. See also ARE. API Applications Programming Interface. A language and message format used by an application program to communicate with another service-providing program, such as an operating system or database management program. APPC Advanced Program-to-Program Communications. A set of IBM protocols, part of its Systems Network Architecture (SNA), that allows executing applications to communicate directly with one another as peers without intervention by a mainframe host. AppleTalk A layered networking protocol developed by Apple Computer that uses a datagram format for communication between Apple Computer products and other computers. This protocol is independent of the network layer on which it is run. application layer The top layer (layer 7) in the OSI reference model that provides communication services such as electronic mail and file transfer. The application layer is concerned with supporting the applications that exchange information (for example, formatting electronic mail messages). APPN Advanced Peer-to-Peer Networking. Network architecture defined within IBM's Systems Applications Architecture (SAA) environment that allows peer-to-peer communication between computers on a network without a mainframe host computer. ARA AppleTalk Remote Access. Provides an asynchronous AppleTalk connection to another Apple Macintosh computer and its network services through a modem. A remote user using ARA can log on to a remote server and mount the volume on the desktop as if it were connected locally. ARAP AppleTalk Remote Access Protocol. Protocol used by remote users to connect to an AppleTalk network. ARB Adaptive rate-based (congestion control). archive site A machine that provides access to a collection of files across the Internet. An anonymous FTP archive site, for example, provides access to materials via the FTP protocol. ARE ATM Routing Engine. Bay Networks processor module that works with high-performance link modules to provide high-level routing and virtual circuit connectivity for routing traffic between multiple LANs. All-Routes Explorer. Frame generated by an end station configured for all-paths broadcast routing that traverses all paths between source and destination end stations.See also am.
ARM Asynchronous response mode. ARNTM Advanced Remote Node. A Bay Networks BayStack access router with multiple LAN interfaces. Slots for WAN adapter modules provide WAN connectivity and facilitate remote network management. ARP Address Resolution Protocol. The Internet protocol used to dynamically bind the low-level, physical, hardware network address to the high-level IP address for a given device. ARP is defined in RFC 826 and limited to physical network systems that support broadcast packets to all devices on the network. ARPANET Advanced Research Projects Agency Network. Research network funded by the Defense Advanced Research Projects Agency (DARPA). Derived from the earlier MILNET, the ARPANET was the original Internet. ARP cache Address Resolution Protocol cache. A table that provides the network and MAC addresses for all devices known to the router. The ARP cache discovery method downloads a list of devices from the router to a specified subnet. All device addresses obtained from each router are added to the database. AS Autonomous system. ASCII American Standard Code for Information Interchange (X3.4-1977). Standard 7-bit coding scheme that assigns unique numeric values to letters, numbers, punctuation, and control characters. ASI Adapter Support Interface. ASIC Application-specific integrated circuit. A silicon chip containing thousands of components designed for a specific application. ASNTM Access Stack Node. Bay Networks stackable (and therefore, scalable) router hardware platform that provides a growth-oriented routing solution. ASN.1 Abstract syntax notation. AssetManagerTM Bay Networks Global Enterprise Management (GEM) application that automates the tracking of network assets. A standards-based automated application for efficient tracking and management of networked assets (such as hubs, routers, bridges), providing fast access to information during problem solving. See also Vision DesktopTM. ASTRAL Alliance for Strategic Token Ring Advancement and Leadership. A multivendor advocacy group created to support token ring users.
asynchronous A method of transmission in which the time intervals between characters are not required to be equal and signals are sourced from independent clocks with different frequencies and phase relationships. Start and stop bits may be added to coordinate character transfer. ATM Asynchronous transfer mode. A set of standard telecommunication interfaces defined by T1, the ATM Forum, and ITU. A switched, connection-oriented, fixed-length cell-based transmission method specifically designed to run at high data rates and to carry a complete range of user traffic, including voice, data, and video signals over long and short distances. ATM uses dedicated media connections running in parallel, allowing simultaneous multiple connections through a single switch device at very high speeds. ATMDXI ATM data exchange interface. A low-cost interface between DTE and DCE devices specified by the ATM Forum. Supports V.35, RS-449, and HSSI DTE-DCE up to 50 Mb/s. ATM Forum A group of public carriers, network equipment vendors, and computer vendors who define interoperability standards for ATM and the deployment of ATM products and services for private LANs, WANs, and public broadband network services. http://www.atmforum.com/ ATM host module The input/output module that provides the ATM services used within a multiple-computer network environment. ATM layer The layer in the ATM model above the physical layer, responsible for cell multiplexing, virtual path identifier (VPI) and virtual channel identifier (VCI) translation, cell header generation/extraction, and generic flow control in customer networks. ATM-SDU ATM service data unit. See also AAL-SDU. ATMSpeedTM Bay Networks configurable and manageable switch modules providing ATM riser connections between wiring closet switches and network center switches. ATM switch Generic term referring to public or private switches. The terms "private ATM switch" and "public ATM switch" are used when a specific requirement or definition applies to ATM switches in a private network or a common carrier network. ATP Advanced technology partner. attachment A port or a pair of ports, optionally including an associated optical bypass, managed as a functional unit. In FDDI, a dual attachment includes two ports: port A and port B. A single attachment includes port S. attenuation The decrease in power or amplitude of a signal as it travels along the wire. attenuator A device used to intentionally decrease, or attenuate, a signal. In fiber, this device dims the light that passes through it.
AUI Attachment (or attached) unit interface. (1) An electrical and mechanical interface defined by the IEEE 802.3 (10 Mb/s) standard, implemented physically as a 15-pin D connector. (2) A connector on the network adapter used to connect cables to fiber optic, coaxial, or 10BASE-T transceivers. AUI cable A cable used to connect the AUI port of a station to an Ethernet transceiver; also called drop cable, transceiver cable, or transceiver drop cable. AURP Apple Update Routing Protocol. Apple Computer routing protocol. Provides efficient use of network bandwidth, increases network security, and enables AppleTalk networks to exchange data through a tunnel. automatic frequency detection A feature of some Bay Networks token ring products that monitors the ring speed of all devices on a token ring. Devices attempting to insert into the token ring at the wrong speed are isolated (wrapped) before they can cause a beaconing condition. Automatic Stack Position Resolution In Bay Networks BayStack and Distributed 5000 implementations, the method by which new modules being added to a stack of hubs resolve their priority within the hub. autonegotiation Enabling two devices that share a common link to advertise their speed capabilities, acknowledge receipt and understanding of shared modes of operation, and reject modes of operation that are not shared. autopartition Process in which a 10BASE-T hub shuts down a port that has produced 31 consecutive collisions or jabber. autopolarity detection A feature of Bay Networks 10BASE-T components that detects and corrects accidental reversal of the wires in a pair. autosense A port's ability to determine the speed of transmission on an attached device, particularly when the device is not capable of autonegotiation or is using a nonstandard form of autonegotiation. AutotopologyTM Part of the Bay Networks Optivity software. A process that automatically recognizes any device on the managed network and defines and maps its relation to other network devices in real time. Autotopology PlusTM An enhanced version of the Bay Networks Optivity mapping software. AWG American Wire Gauge. B8ZS Binary 8 Zero Suppression. An alternate line coding parameter (setting) option to AMI, with relation to editing of T1 and WAN router software services.
B channel Bearer channel. Part of an ISDN interface able to carry voice or data over an ISDN network at 64 Kb/s. See also D channel. Backbone Concentrator Node (BCN®) Bay Networks multiprotocol router/bridge hardware platform with 13 expansion slots and up to four power supplies. Backbone Concentrator Node Switch (BCNXTM) Bay Networks layer 2 switch combined with a layer 3 router that routes or switches packets across the BCN backplane. Integrated switch/routing solution for large networks. Backbone Link Node (BLN®) Bay Networks multiprotocol router/bridge hardware platform with four expansion slots. Backbone Link Node Switch (BLNXTM) Bay Networks layer 2 switch combined with a layer 3 router that routes or switches packets across the BLN backplane. backbone network The main segment of a network to which all other segments are connected. It links several workgroup LANs together in a single building, or several networks together in a campus environment. All systems with connectivity to the backbone have connectivity to one another, but systems can set up private connections that bypass the backbone for reasons of cost, performance, or security. Backbone Node (BN®) Bay Networks router hardware platform family that includes the BCN and the BLN platforms. Symmetric multiprocessor architecture provides high performance, distributing processing power to each network interface module. backbone segment A single segment located on the backplane of the network center hub or router that provides the interconnect point for other segments or remote networks. backoff error Ethernet NMM error indicating that a station attempting to transmit did not wait long enough following a collision before attempting to retransmit. Could be caused by a faulty NIC card. backplane A printed circuit board in a hub that contains slots for plugging in modules and provides the physical connection for the network interface. backplane segment A segment that resides on the backplane of a System 3000 or System 5000 hub, used when assigning clusters from different host modules to the same segment, ring, or FDDI network. BAN Boundary Access Node. An IBM enhancement that refers to the RFC 1490 specification for bridged SNA over frame relay. BAN carries the source and destination MAC addresses in the network packets. Bay Networks routers automatically select BAN with frame relay networks using source-route encapsulation.
bandwidth The data-carrying capacity of a transmission medium, usually measured in cycles per second (Hertz). Represents the difference between the highest and lowest frequencies available for signals. The bandwidth varies based on the transmission method employed. bandwidth-on-demand A WAN service that maintains dial-up internetworking performance levels by establishing supplemental dial connections when a leased-line or packet-switched link becomes congested. barrel connector A connector that joins two cable segments together to form a longer cable. BNC barrel connectors join thin Ethernet cable, and N-series connectors join standard Ethernet cable. See also BNC connector. baseband A communications method where digital signals are pulsed directly on the transmission medium without change in modulation. In baseband LANs, the entire bandwidth of the cable is used to transmit a single signal and only one signal can be transmitted at a time. See also broadband. baud The signaling rate of a line; the number of voltage or frequency transitions per second. At low speeds only, baud may be equal to bits per second. BayDSPTM Bay Networks Digital Signal Processor. A Bay Networks product using digital modem technology to provide more call density, reliability, and statistical information than analog modems. BayDVSTM Bay Networks Dial Virtual Private Network Services. A network providing secure remote dial access services and switched connectivity to VPNs. BayRSTM Bay Networks Routing Services. Services provided by Bay Networks routers that maximize connectivity and interoperability in multivendor, multiprotocol environments by supporting all major network and bridging protocols. BaySecureTM Bay Networks security framework that includes LAN access, remote access, and routing services security implementations. BaySISTM Bay Networks Switched Internetworking Services. A switched internetworking architecture combining switching technology with the traditional shared-media hub and router technologies. BayStack Advanced Remote Node (ARN) A Bay Networks access router with multiple LAN interfaces. Slots for WAN adapter modules provide WAN connectivity and facilitate remote network management. BayStackTM hubs Bay Networks Ethernet stackable hubs with lower end network manageBay Networks multiservice software that delivers WAN functionality using IPC Virtual Circuit (IPVCTM) technology to integrate frame relay switching and interworking with IP routing to provide scalability and management for emerging IP-based technologies. BCCTM Bay Command Console. An object-oriented command-line interface for configuring various Bay Networks devices, such as routers.
Block check character. BCN® Backbone Concentrator Node. Bay Networks multiprotocol router/bridge with 13 expansion slots and up to four power supplies. BCNX Backbone Concentrator Node Switch. Bay Networks layer 2 switch combined with a layer 3 router that routes or switches packets across the BCN backplane Integrated switch/routing solution for large networks. BDR Backup designated router. beacon In a token ring network, a frame sent by a token ring adapter to indicate a serious ring problem, such as a broken cable. An adapter is said to be beaconing if it is sending such a frame. The problem must be resolved for communications to resume. beacon resolution Ability in Bay Networks token ring products to automatically bypass a faulty station or equipment and allow a ring to continue to function. BECN Backward explicit congestion notification. Bits within a frame relay header to indicate congestion in the path in the opposite direction as the frame is flowing. See also FECN. BER Bit error rate. The number of erroneous bits in a data transmission. Berkeley Software Distribution (BSD) Implementation of the UNIX operating system and its utilities developed and distributed by the University of California at Berkeley; usually preceded by the version number of the distribution. Many Internet hosts run BSD software. BERT Bit Error Rate Test. A common test for WAN lines. BFE Blacker front-end encryption. BGP Border Gateway Protocol. A protocol in the IP suite designed to exchange network reachability information with other BGP systems in other autonomous systems. BGP speakers provide routing updates including a network number, a list of autonomous systems that the routing information has passed through, and a list of other path attributes. BGP4 replaces the original BGP3, although both are supported by Bay Networks. BIND Domain Implementation of a Novell NetWare Domain Name Server (DNS) developed and distributed by the University of California at Berkeley. Many Internet hosts run BIND, and it is the ancestor of many commercial BIND implementations. BIOS Basic input/output system. In a PC, a set of instructions at a specific address that allows the computer operating system to communicate with applications and peripheral devices.
B-ISDN Broadband Integrated Services Digital Network. Broadband aspects of integrated services digital network, a high-speed communications standard for WANs for high-bandwidth applications (video, voice, and graphics). bit-oriented protocol A communication protocol that does not recognize character boundaries or special protocol characters. The data is interpreted as sequence of bits. bit rate The base transmission rate at which user data is sent. BLER Block error rate. BLERT Block error rate test. BLN® Backbone Link Node. A multiprotocol router/bridge with four expansion slots. BLN-2 Backbone Link Node-2. Bay Networks BLN router/bridge with two power supplies. BLNX Backbone Link Node Switch. Bay Networks layer 2 switch combined with a layer 3 router that routes or switches packets across the BLN backplane. block A unit of information consisting of a header and an information field. BN® Backbone Node. Bay Networks router hardware platform family that includes the BCN and the BLN platforms. BNC connector A small coaxial connector with a half-twist (bayonet) locking shell. Depending on the source, BNC stands for British Naval Connector, Barrel Nut Connector, Bayonet Nut Coupling, or Bayonet-Neill-Concelman after Paul Neill and Carl Concelman. Also referred to as a BNC T-connector. BNCP Bridge Network Control Protocol. BNN Boundary Network Node. An IBM router enhancement that refers to the RFC 1490 specification for routed SNA over frame relay. BNN allows native SNA traffic to communicate over public or private frame relay networks directly with an SNA processor. BNN does not carry the source and destination MAC addresses in the network packet. Bay Networks routers automatically select BNN with frame relay networks configured without source-route encapsulation. BNI Boundary Network Identifier.
BNX® Broadband Enterprise Switch. Network access switching software for switched networks using frame relay, SMDS, IP routing, or ATM service internetworking technology. Predecessor to Bay Networks BayStream multiservice software. BOC Bell Operating Company. BofL Breath of Life (message or packet). Bay Networks proprietary polling messages sent over Ethernet and FDDI interfaces to all systems on the local network or over a WAN point-to-point connection between the local router and a remote peer. The exchange of BofL messages establishes connectivity when the interface is idle. BONDING Bandwidth ON Demand INternetworking Group. A nonstandard method for using 2 ISDN B channels to create a 128 Kb/s switched line. booting The process in which a device obtains startup information and begins to process it to attain a state of normal operation. BootP Bootstrap Protocol, described in RFC 951. A standard protocol used to provide startup information to a client device from a server. BootP Request A request from a client device to be configured and booted. BOT Binary Synchronous Communication (BSC) over TCP/IP, a Bay Networks router feature. BPDU Bridge Protocol Data Unit. A data unit containing information passed between connected stations regarding connection status. bps bits per second; also abbreviated b/s. BPV Bipolar Violation. T1 line code/signal errors. brdg Bridge. See bridge. BRI Basic rate interface or basic rate ISDN. An Integrated Services Digital Network (ISDN) service with two B channels with 64 Kb/s bandwidth for data and one D channel of 16 Kb/s for signaling and control information. See also ISDN, PRI. bridge A device that links two or more local area networks, monitors packets on the connected networks, and forwards only packets destined for the other network. Bridges function at the data link layer (MAC layer) of the OSI reference model and selectively filter or forward traffic, based on the destination address of the frame.
BridgeManTM Bay Networks software application that functions as an alternative to an onboard manager. In conjunction with Lattis EZ-View or LattisNet Manager for DOS applications, BridgeMan allows a network administrator to change bridge operating parameters while the bridge is active and to display real-time fault and performance data. broadband Data-transmission technique that allows multiple simultaneous signals to share a transmission medium bandwidth by using radio frequency (rf) modulation. The total capacity of the medium is divided into multiple, independent bandwidth channels, where each channel supports an independent network and occupies a specific frequency range. Thus several networks are able to coexist on a single cable. See also baseband. broadcast A message sent to all nodes or an address for all nodes on a network. A special type of multicast packet that all nodes on the network are always willing to receive. See also multicast. broadcast domain A group of destination stations to which a broadcast frame is transmitted from an end station. The boundaries of a broadcast domain are defined by the connecting device(s), such as a router. broadcast packet A group of bits sent to all nodes on the network at the same time. A function of the MAC address, a broadcast is a special form of a multicast in which the subnet of devices to receive a copy of the packet consists of the entire network. Also called a broadcast frame. broadcast storm Congestion on a network caused when multiple hosts respond all at once to a transmission from a workstation, which causes the performance of the network to slow exponentially or even halt operations. b/s bits per second; also abbreviated bps. BSAC BaySecure Access Control. Bay Networks implementation of the IETF RADIUS security standard for a mechanism of information exchange between a device that provides network access to users and a device that contains user authentication and profile information. See also RADIUS. BSC Binary Synchronous Communication. A data transmission protocol for multiprotocol backbone networks. BSD Berkeley Software Distribution. Implementation of the UNIX operating system and its utilities developed and distributed by the University of California at Berkeley; usually preceded by the version number of the distribution. Many Internet hosts run BSD software. BTS BSC Transport Services. See also BSC. burst error A token ring error in which the adapter detects the absence of transmissions for five half-bit times between the starting delimiter and the ending delimiter.
bus An internal data path. Typically an electrical connection, with one or more conductors, where all attached devices are logically connected. BUS Broadcast and unknown server. On an ATM network, part of the multicast server (MCS) software that provides broadcast service for each virtual LAN. bus error An error in the electronic pathway that carries signals from one part of a computer to another. bus topology A network topology in which all nodes are connected to a single coaxial cable and thus share a single channel. The cable is referred to as a backbone. Bus topology is rarely used for local area networks today because it is relatively difficult to add or change users or to troubleshoot. See also ring topology, star topology. byte A group of bits (usually eight), also known as an octet, derived from BinarY digiT Eight. A byte usually holds a single character, such as a number or letter. Octet is the more precise term, however, because some systems use bytes that are other than eight bits long. byte-oriented protocol Communications protocol that calls for data to be transferred as a series of bytes or characters. Control characters are separate from data. This protocol is found in most asynchronous protocols using modems. C50 The Bay Networks Centillion 50 chassis delivering 3.2 Gb/s backplane capacity and supporting ATM switching. The C50 chassis provides three module slots. C100 The Bay Networks Centillion 100 family of ATM-core LAN-to-LAN, LAN-to-ATM, and ATM-to-ATM modular switching devices supporting token ring, Ethernet, and ATM with integrated frame and cell switching. The C100 chassis provides six module slots. C1000 The Bay Networks Centillion 1000 family of high-capacity multiservice ATM switches, delivering switching solutions to enterprise networks. Various chassis models provide 16, eight, or four slots. cable An electrical copper or optical fiber transmission medium that carries data in a network. A group of individually insulated conductors in twisted or parallel configuration, usually with a jacket. cable adapter A connector that enables dissimilar kinds of cables or connectors to be joined with one another. cabling distribution system Building wiring that runs from network stations to wiring closets or between wiring closets; also called premises wiring. cabling medium (type) the physical medium over which electronic transmission occurs. Examples are coaxial, unshielded twisted pair (UTP), shielded twisted pair (STP), and fiber.
CAC Connection admission control. A set of actions taken at a virtual circuit or virtual path connection setup to determine if the connection can be accepted. The decision is based on the anticipated traffic at the virtual circuit, the quality of service (QoS) requirements, and the current network load. call management The collecting of information from a Remote Access Concentrator (RAC), storing the information in a database, and generating reports from the database. Call statistics may be used for capacity planning and traffic troubleshooting. See also Optivity Call ReporterTM. CAM Channel access method. Computer-aided manufacturing. Content addressable memory. campus (network) A departmental LAN spread over multiple buildings. For example, this environment can be present in a small company or a division of a larger company. CAP Carrier Amplitude/Phase modulation, associated with xDSL technologies. card A printed circuit board that fits into a slot in a personal computer. CAS Channel associated signaling. cascade Interconnection of devices, typically hubs, that allows those devices to act together as a logical repeater. cascaded segment A repeater bus that extends between multiple units in the Distributed 5000 hub. Analogous to a System 5000 Ethernet backplane segment. Category 3, 4, 5 Categories of unshielded twisted pair cable. Category 3 is voice grade cable. Categories 4 and 5 have more twists of the internal wire pairs and tighter tolerances with progressively better attenuation and crosstalk specifications. Category 4 is used at speeds up to 20 Mb/s, including 16 Mb/s token ring. Category 5 is used at speeds up to 100 Mb/s, including FDDI (TP-PMD), 100BASE-T, and potentially for ATM at 155 Mb/s. catenet A network in which hosts are connected to networks with varying characteristics and the networks are interconnected by gateways (routers). The Internet is an example of a catenet. CBR service Constant bit rate service. A type of telecommunication service characterized by a service bit rate specified by a constant value. CCE Configuration control elements. Functionality related to management of FDDI paths and stations. Bay Networks FDDI products use a larger set of functions (in the form of integrated circuits) referred to as path switching elements (PSE). See also PSE.
CC Call control. A wireless communication term. CCC Clear coded channel. CCIS Common channel interoffice signaling. CCITT Consultative Committee on International Telegraph and Telephone. An obsolete term, now the International Telecommunication Union-Telecommunications sector (ITU-T). The ITU-T is part of the United Nations International Telecommunication Union (ITU), responsible for making technical recommendations about analog and digital telephone and data communications systems. http://www.itu.ch/home/ CD Carrier detection. (1) A signal sent from a modem to a computer to indicate that it is online. (2) In RS-232 transmission, a signal that indicates that a connection has been made by sensing a line carrier frequency. The ability to detect when multiple stations are trying to access the transmission channel. In Ethernet CSMA/CD, this event is normal. Stations are designed to back off, then try again after a random interval. See also collision domain. CDDI Copper Distributed Data Interface. Cisco Systems version of FDDI that uses UTP wires instead of optical fiber. See also TP-PMD. CD-ROM Compact disc read-only memory. cell A 53-byte protocol data unit (PDU) used in ATM technology for transporting information. Its fixed size contains a 5-octet header and a 48-octet body. See also PDU. cell delineation The identification of cell boundaries in an ATM cell stream. cell header An ATM layer, protocol control information. The 5-octet data field at the beginning of an ATM cell. See also protocol control information. cell relay Form of packet transmission using a 53-byte cell, used in B-ISDN networks. Also known as ATM. cell switch A switch that operates on fixed-length cells to provide direct, virtual circuit connections. ATM uses cell switching. cell transfer delay The elapsed time between cell exit and entry, as measured by points on a particular ATM connection. See also cell.
CentillionTM A family of Bay Networks ATM switching products. Centillion 10TM switches Bay Networks token ring switches for workgroup applications. Centillion 100TM switches Bay Networks ATM-core LAN-to-LAN, LAN-to-ATM, and ATM-to-ATM modular switching devices supporting token ring, Ethernet, and ATM with integrated frame and cell switching. Centillion 1000TM switches Bay Networks family of high-capacity multiservice ATM switches, delivering switching solutions to enterprise networks. Various chassis models provide 16, eight, or four slots. Centillion 50TM switches Bay Networks chassis delivering 3.2 Gb/s backplane capacity, supporting ATM switching. The C50 chassis provides three module slots. CEPT Conference on European Posts and Telecommunications. An organization defining E1 standards, comparable to US T1 standards. See also PTT. CFM Configuration management. (1) One of the five functional application areas for network management defined by the ISO, concerned with installing, initializing, loading, modifying, and tracking the configuration parameters of network hardware and software. (2) The addition, modification, or deletion of information that defines the behavior of an application, computer, or network device. CGA Color graphics adapter. channel A path (electrical or logical) along which signals can be sent between points. CHAP Challenge Handshake Authentication Protocol. A method of establishing security on PPP links where the peers must share a plaintext "secret." The caller sends a challenge message to its receiving peer and the receiver responds with a value it calculates based on the secret. The first peer then matches the response with its own calculation of what the response should be. If the values match, the link is established. CHAP secret The value used by two peers in establishing a PPP connection using the Challenge Handshake Authentication Protocol (CHAP). chassis A housing designed to accommodate modular and other electronic components. A chassis provides power and a connecting backplane for modules. CHINs Community Hospital Information Networks.
CIDR Classless interdomain routing. An address aggregation scheme that employs supernet addresses to represent multiple IP destinations. Rather than advertise a separate route for each destination, a router uses a supernet address to advertise a single route (called an aggregate route) representing all destinations. CIR Committed Information Rate. A specific level of traffic wherein frame relay networks should experience no or low packet loss. circuit switching A communications model in which a dedicated communication path is established between two hosts and on which all packets travel, open only for the duration of the transmission. Once the connection is closed, other devices can use it. The telephone system is an example of a circuit switched network. See also connectionless, connection-oriented, packet switching. circuit transfer mode A transfer mode in which transmission and switching functions are achieved by permanent allocation of channels/bandwidth between the connections. CLAMTM Corporate LAN Access Module. Bay Networks router in the NauticaTM family with optional analog voice card. Class A/B/C/D Different types of ATM service: Class A requires end-to-end timing, requires a constant bit rate, and is connection oriented. Class B requires end-to-end timing, requires a variable bit rate, and is connection oriented. Class C does not require end-to-end timing, supports a variable bit rate, and is connection oriented. Class D does not require end-to-end timing, supports a variable bit rate, and is connectionless. Class A/B/C address In a TCP/IP network, the format of the IP address: Class A: the first byte (8 bits) is the network portion; the remaining three bytes (24 bits) contain the subnet and host address. Used in very large networks. Class B: the first two bytes (16 bits) are network; the remaining two bytes (16 bits) contain the subnet and host address. Used in medium-size networks. Class C: the highest three bytes (24 bits) are the network field; the remaining byte (8 bits) contains the subnet and host address. Used in small networks. Class A/B Certification FCC certification that a given computer product meets specified limits for radio frequency emissions. Class A certification, designed for commercial and industrial environments, is less stringent than Class B certification, designed for homes and home offices, where the device is more likely to interfere with radio and television reception. CLEC Competitive Local Exchange Carrier. A telecommunication company utilizing an incumbent carrier's telecom facilities in conjunction with its own localized equipment to provide unregulated, modern services. CLI Calling line identification. The directory number of the caller provided by the telephone company to the party called during call setup. Also referred to as Caller ID. Command line interface. A mechanism for initiating and managing system network operations using a set of operator-entered alphanumeric commands instead of a graphical user interface (GUI).
client A computer system or process that requests a service of another computer system or process. A workstation requesting the contents of a file from a file server is a client of the file server. client/server model A software model in which a "client" entity (typically a local workstation or software routine) requests and receives services from a "server" entity (a dedicated remote server system or subsystem). A client interacts with the user and may request services from multiple servers. CLNP Connectionless Network Protocol. OSI protocol using CLNS for data delivery. CLNS Connectionless network service. Method of data delivery using datagrams with addressing information to route messages on LANs. The OSI equivalent of IP. CLP Cell loss priority. Part of the ATM cell header that indicates the priority of the cell and whether or not the network can discard it under heavy traffic conditions. cluster A group of ports on a host module or other networking device, indivisible in terms of segment assignment and used to facilitate segment and ring management. A cluster an consist of just one port on a host module, a few ports, or all the ports on a module. CM Cable Modem. Bay Networks Versalar CM product based on DOCSIS, designed for the broadband services industry. See also DOCSIS, VersalarTM. CMB Common management bus. Bay Networks network management interface in System 5000 and Distributed 5000 hubs that also supports communications with other modules. CMIP Commn Management Information Protocol. The OSI network management standard for exchange of management directives and responses. CMIS Common Management Information Services. The OSI standard functions for network monitoring and control. CMOL CMIP over LLC. See also CMIP, LLC. CMOT Common Management Information and Services Protocol Over TCP (CMIP Over TCP/IP). An Internet standard defining the use of CMIP for managing TCP/IP local area networks. Also abbreviated CMPT. CMPT Common Management Information and Services Protocol over TCP. See also CMOT. CMSTM Connection Management SystemTM. Software used in Bay Networks ATM networks that provides connection services within the network for initial switch setup and normal operation.
CMT Common mode termination. Termination of unused pairs of wire in a four-pair cable to reduce the antenna effect of the unused pairs. CMT improves emission and susceptibility performance. CMTS Cable modem termination system. Bay Networks Versalar CMTS product based on DOCSIS, designed for the broadband services industry. See also DOCSIS, VersalarTM. CN® Concentrator Node. An early Bay Networks multiprotocol router with 52 LAN/WAN interfaces. coaxial cable A type of network transmission medium. Transmission line that contains a copper inner conductor surrounded by plastic insulation and a woven copper or foil shield. Used in original Ethernet and broadband premises wiring systems. COI Community of interest. collapsed backbone network A segmented network architecture with centralized internetworking facilitated by a router. In this configuration, resources are controlled in a centralized location called the network center and all users are connected to a common network, which originates in this center. collision The result of two stations trying to send packets at the same time, which causes fragments or garbled data (mutual destruction of the colliding packets). Collisions are normal in an Ethernet network. The CSMA/CD access method is designed to quickly restore the network to normal activity after a collision. See also CD, CSMA/CD. collision domain Within Ethernet (IEEE 802.3), a portion of a network that includes cable segments, attached devices, and repeaters, arranged in such a fashion that any two devices share the same transmission channel. communications adapter An expansion circuit board that goes inside each device (for example, PC, workstation, server, or DTE/DCE) on the network and allows that device to listen and talk to other stations and nodes on the network. communications closet A central building or room where distribution cabling is switched and terminated and where voice and data communications equipment are located; also called equipment room, telecommunications closet, or wiring closet. compression A routing feature that eliminates redundancy in data streams, reducing the amount of bandwidth required to transport LAN protocols over a wide area. A method of encoding large amounts of data into a smaller data format that requires a smaller amount of bandwidth for transmission over a network. Supported over frame relay, X.25, and PPP (dial-up lines or leased lines). concentrator (1) A network device that "concentrates" or combines multiple slower-speed communication channels into a single, higher-bandwidth channel. (2) A physical layer device connected to several other devices that restores a signal's amplitude and timing for transfer across a LAN. The device is known as a repeater in most IEEE 802.3 standards. A concentrator provides Ethernet, FDDI, and/or token ring connectivity and accepts host, network communications, and
network management modules. Also called a hub. configuration (1) Information retrieved by an operating system from a local storage medium or remote server that defines the behavior of an application, computer, or network device. (2) The total combination and setup of hardware components (such as CPU, display device, and printer) and programs that make up a computer system, subsystem, or network. (3) The arrangement of a computer system or network as defined by the nature, number, and chief characteristics of its functional units. The term may refer to a hardware or a software configuration. (4) The process of specifying the appropriate parameters to customize network software. configuration file A binary or ASCII file containing information that defines the behavior of an application, computer, or network device. configuration switching The association of a port on an intelligent hub host module with any one of the various backplane segments built into that hub via software. Also referred to as port switching. congestion Condition that occurs when the offered load nears or exceeds the capacity of a data communication path. connection (1) A path for reliable communication between two network entities. The path can be physical or logical, and the entities can be hardware/software systems or subsystems and/or subsystems attached to the network medium. (2) The path between two networking protocol modules that provides reliable stream delivery service. connection-oriented Transmissions that require a connection to be established prior to the transmission. connectionless Transmissions that do not require a direct connection prior to the transmission. Source and destination addresses are included in each packet. connectionless service The IEEE set of services by which peer entities can exchange protocol data units (PDUs) without the establishment of a connection. See also CLNS. connectivity The act of communicating between computers and terminals; the property of a network that allows dissimilar devices to communicate with one another. CONS Connection-Oriented Network Service. OSI protocol providing service for data delivery. Considered more efficient for WANs than for LANs. constant bit rate (CBR) service A type of telecommunication service characterized by a service bit rate specified by a constant value. ContivityTM Extranet Switch Bay Networks product family providing secure and reliable extranet access over public networks, that is, Virtual Private Networks (VPNs). Contivity products includeExtranet Switches 4000, 2000, and 1000. See also Extranet, tunneling, VPN.
convergence time The time it takes for routers in a network to detect a change in the network topology and recompute all known routes. The time it takes for devices in the network to "converge" on an accurate definition of routes. Conversation Steering ControlTM Bay Networks filtering technique utilizing multiple filters to support two-way conversations to allow remote monitoring on demand. Corporate LAN Access Module (CLAMTM) Bay Networks router in the Nautica family with optional analog voice card. COS Class of service. CP Control point. CPCS Common part convergence sublayer. CPE Customer Premise Equipment, also Customer Provided Equipment. cps Characters per second; also c/s. CPU Central processing unit. CRC Cyclic redundancy check. An error detection method used to verify the integrity of a packet. See also CRC error. CRC error Cyclic redundancy check error. An error condition in which the data failed a checksum test used to trap transmission errors. These errors can indicate problems anywhere in the transmission path. cross-connect A system, chassis, or rack unit containing the electrical (wire), optical (fiber), or digital means to centrally interconnect network devices attached to a premises wiring system. In a wire cross-connect, jumper wires or patch cords are used to make circuit connections. In an optical cross-connect, fiber patch cords are used. See also DACS. crossover A wiring function that connects the transmitter at one end of the link to the receiver at the other, either externally or internally. crosspoint switch matrix Creates dedicated physical paths between any switch input ports based on the desired destination. Takes the place of a shared bus in conventional devices. crosstalk noise generated in one circuit by a signal in an adjacent circuit.
CSLIP Compressed Serial Line Internet Protocol (IP) is a compressed version of the SLIP protocol. See also SLIP. CSMA Carrier sense multiple access. A local area network access technique in which multiple stations connected to the same media channel can sense transmission activity on the medium and defer initiating transmission while the channel is active. CSMA/CA Carrier sense multiple access/collision avoidance. Access scheme to increase Ethernet performance by having an intelligent hub intervene when a collision is detected and "decide" in a fraction of a nanosecond which message is ahead and will be sent. Generally, the transmitter closest to the hub receives priority transmission because of its proximity to the hub, not necessarily because it transmitted first. CSMA/CD Carrier sense multiple access/collision detection. Access method used by stations connected to an Ethernet LAN, defined by the IEEE 802.3 specification. Stations contend for access to the shared media, and a collision results if two stations send packets at the same time. Collisions are normal, and the CSMA/CD method quickly restores the network to normal activity. CS-PDU Convergence sublayer packet data unit. CSU Channel service unit. Device that acts as a safe electrical buffer between the customer and a public WAN to prevent faulty equipment from affecting the network. CTS Clear to send. Hardware signal used in RS-232 interface connections. An enabling signal generated by a receiving device, indicating (to a sending device) that it is ready to receive data. CUG Closed user group. CUGOA Closed user group with outgoing access. D4 D4 Superframe, or frame. One of the two T1 frame formats, ESF being the other. See also ESF. D channel The channel used for signaling data on an ISDN network. It operates on transmission speeds of 16 Kb/s or 64 Kb/s, depending on the interface used. See also B channel. D connector An electrical connector with a D-shaped shell. DA Destination address. In an FDDI frame and token ring block, the station(s) for which the frame is intended. Addresses can be either 16 or 48 bits long. In an Ethernet packet, the field that consists of the first 6 bytes (48 bits) of the packet following the preamble and start bit. DAC Dual attached concentrator or dual attachment concentrator. A hub that is attached to both rings of an FDDI network or that offers a dual attachment to the FDDI network and is capable of accommodating a dual (primary and secondary counter-rotating) ring.
DACS Digital access and crossconnect system. A digital switching device for routing and switching T1 lines among multiple T1 ports. It performs the functions of a normal "switch," except connections are typically set up in advance of the call, not with the call as in most low-bandwidth communications. daemon An unattended background process that is continually running on a UNIX-based host computer. An application typically calls up a daemon to perform a standard routine or service, and the daemon processes the request. DAP Data Access Protocol. DARPA Defense Advanced Research Projects Agency (formerly ARPA). The U.S. government agency that funded research and experimentation with the ARPANET and later the Internet. See also ARPANET. DAS Dual attached station or dual attachment station. An FDDI station that attaches to one or two higher-level concentrators in a dual homed configuration. See also dual homing. data connector A four-position connector used in the IBM Cabling System. data path A logical point-to-point channel that is a permanent leased line. See also multiline circuit. DB-9 A 9-pin serial connector with a D-shaped shell, often used to implement a subset of the EIA RS-232 interface, or used in STP cable plant connections. DB-15 A 15-pin serial connector with a D-shaped shell used to implement the IEEE 802.3 attachment unit interface. DB-25 A 25-pin serial connector with a D-shaped shell used to implement the EIA RS-232 interface. dBm decibel referenced to 1 milliwatt (mW) used to refer to relative strength of a signal. At 0 dBm, a signal delivers 1 mW to a line load. DCALS Defense Department Computer-aided Acquisition and Logistics Support. DCD Data carrier detect. A hardware signal defined by RS-232-C that indicates that a device (modem) is online and ready to transmit. DCE Data communication equipment. A device that establishes and maintains a network interface session. DCE devices, such as modems, connect to data terminal equipment (DTE) devices, such as computers, using an RS-232 or CCITT V.24 standard interface. See also DTE.
Data Collection Engine. An onboard card that can be installed on an Ethernet or token ring network management module or a daughtercard that provides RMON support for a Distributed 5000 hub, a BayStack Ethernet hub, or a BayStack AN Router. A DCE monitors a single Ethernet segment or token ring by collecting data for use in analyzing performance, topology, fault, usage, and protocols. DCM Data collection management or data collection module. In Bay Networks Distributed 5000, a daughterboard module that upgrades the NMM to provide Advanced Analyzer agent capability with RMON and RMON2 capabilities. DCMMW DCM middleware. A software subsystem used by a router to communicate with the DCM software on the Ethernet DCM. See also middleware. DDCMP Digital Data Communication Message Protocol. A byte-oriented synchronous protocol developed by Digital Equipment Corporation that supports half- or full-duplex modes and either point-to-point or multipoint lines in a DNA (Digital Network Architecture) network. DDE Dynamic data exchange. A form of interprocess communication that uses shared memory to exchange data between applications. Applications can use a one-time data transfer or ongoing exchanges. DDN Defense Data Network (X.25). Used loosely to refer to the MILNET, the ARPANET, and the TCP/IP protocols they use. A network containing Department of Defense information. DDP Datagram Delivery Protocol. Unreliable network layer routing protocol developed by Apple Computer as part of the AppleTalk network, used to transmit packets between nodes on the network. DDS Dataphone Digital Service. An AT&T private line digital service with data rates to 56 Kb/s. Private analog lines can be connected to DDS lines. Digital Data Service. A private line digital service from a non-AT&T carrier. DE Discard eligible. DECnet A proprietary peer-to-peer network technology originally developed by Digital Equipment Corporation for use in wide area networking and evolved to include significant Ethernet-based LAN capabilities. DecodeManTM Bay Networks application included with Optivity software used to troubleshoot remote devices by displaying full 7-layer RMON protocol decodes for major protocols. dedicated LAN A configuration where a single end station is connected to a switch port, giving it an uncontested 10 Mb/s Ethernet LAN all to itself, with no possibility of collisions. Also referred to as a private LAN. See also micro-segmentation.
default gateway Often called an IP router, a gateway connects two or more networks or subnets, enabling the passage of data from one subnet to another. The default gateway is the router for the local subnet. default router A routing table entry that is used to direct packets addressed to networks not explicitly listed in the routing table. DEN Directory Enabled Networks. An effort to specify a directory services information model and schema for distributed applications, management tools, and network elements. http://murchiso.com/den/ DEP Directory-Enabled Provisioning. A feature of Bay Networks Extranet Switch products to simplify management and deployment of Extranet switches. department concentrator A modular hub suitable for smaller networks. DesignManTM Part of the Bay Networks Optivity network management software. Provides automatic data collection, Ethernet traffic analysis, and switch simulation in a graphics-based network design tool. deterministic; ATM deterministic A form of the asynchronous transfer mode in which a constant information transfer capacity expressed in terms of a predetermined limiting value for a given service is provided to the user throughout a call. DFC Data flow control. See also flow control. DFF Design for Fabrication. DFM Design for Manufacturing/Manufacturability. DFT Design for Testability. DGTP Data grade twisted pair. A type of unshielded twisted pair wiring designed to carry high-frequency signals. DHCP Dynamic Host Configuration Protocol. Ethernet protocol widely used in heterogeneous networks (such as those that support Windows NT® and other multiple protocols) that provides a centralized administration point for managing multiple operating systems. dial back Security mechanism used in remote dial access. The server authenticates the user, hangs up, and dials the user back on a different telephone line, thus ensuring that the user is calling from an authorized location. dial-on-demand A service that extends internetworking connectivity to small users on an as-needed basis, without requiring dedicated links, leased-line, or packet-switched services.
dial-up connection A temporary, as opposed to dedicated, connection between machines established over an analog or digital phone line. Also called a switched connection. D-inside wire (DIW) An inexpensive unshielded twisted pair wire typically installed as the building cable for telephone systems. Predates and does not quite meet Category 3 cabling specifications, but does meet 10BASE-T requirements. Also called voice grade twisted pair. DIP switch Dual in-line package switch. directed broadcast device Device that allows multiple unique broadcast domains to be created over a single, unified physical infrastructure. Users are assigned to broadcast domains to create logical networks, establishing direct switched connectivity between users and servers, independent of their physical attachment to the network. Router ports provide communication between logical networks. The Bay Networks LattisSwitch and EtherCell/LattisCell/MCS/CMS system are examples of directed broadcast products. DIS Draft International Standard. A development step near final status on an ISO specification. distance vector protocol A routing protocol that defines the best direct route between a source and its destination, in terms of the number of routing hops, regardless of speed. Routing Information Protocol (RIP) is an example of a distance vector protocol. See also RIP. Distributed 5000TM Bay Networks stackable switching hubs for midsize Ethernet networks. distributed backbone network A segmented network architecture with physically distributed internetworking. In this configuration, hubs connect groups of users, and routers connect the hubs to a backbone segment, usually FDDI. The hubs and routers are dispersed. distributed retiming Process by which an Ethernet host module, such as Bay Networks System 5000, provides retiming for its own segments. distribution cabling building wiring that runs from network stations to wiring closets or between wiring closets; also called premises wiring. DIW D-inside wire. An inexpensive unshielded twisted pair wire typically installed as the building cable for telephone systems. Predates and does not quite meet Category 3 cabling specifications, but does meet 10BASE-T requirements. Also called voice grade twisted pair. DIX DEC/Intel/Xerox. Used to refer to an early version of Ethernet. DIX connector DEC/Intel/Xerox AUI style (standard Ethernet) 15-pin D connector used for AUI connections on Ethernet. DLCI Data link connection identifier. A device designating a path between a source and its destination.
Data link control interface. DLC layer Data link control layer. Layer 2 of IBM's Systems Network Architecture (SNA). DLCMI Data link control management interface. DLL Data link layer. Layer 2 of the OSI reference model, responsible for data transfer across a single physical connection or series of bridged connections between two network entities. Defines protocols governing the creation of data packets and transmission into and out of each node. Includes the logical link control (LLC) and media access control (MAC) sublayers. See also LLC, MAC. Dynamic Link Library. A program module that contains executable code and data that can be used by other applications to perform a specific task. DLSw Data link switching. A standards-based mechanism for reliably transporting connection-oriented SNA and NetBIOS data across multiprotocol network backbones. Defined in RFCs 1434 and 1795. DLUR Dependent logical unit requester. DLUS Dependent LU server. DM Disconnected mode. DMA Direct memory access. The process of transferring data directly from a storage device such as a hard disk into memory without going through a processor. DMT Discrete Multitone Technology, associated with xDSL technologies. Design Maturity Test. DMTF Desktop Management Task Force. An industry consortium developing, supporting and maintaining industry standards for PC management. http://www.dmtf.org/ DN Distinguished name. A collection of attributes, referring to an LDAP directory entry. See also LDAP. DNA Digital network architecture. Defines the protocols, formats, and control of message exchange implemented in Digital Equipment Corporation's DECnet network. DNIC Data Network Interface Circuit. An ISDN U Interface.
Data Network Identification Code. An address used by routers using the X.25 protocol to reach a host residing on a different packet-switched network. DNIS Dialed Number Identification Service. A call association/processing application that informs the service operator of the telephone number the caller dialed. See also ANI. DNS Domain name server or domain name service. Addressing system that incorporates the domain name into the IP address. As used on the Internet, some of the domains are: .gov (U.S. government), .edu (educational institution), and .com (commercial organization). DOCSIS Data Over Cable Service Interface Specifications. A project developing standard communications and service specifications for cable modems and associated equipment for the North American cable industry. See also MCNS. http://www.cablemodem.com/ DoD Department of Defense, U.S. Government. domain A collection of network devices that form a subgroup of a network. A domain can be created for logical, functional, or geographic purposes and range from top level to local. Part of the name hierarchy on the Internet. All of the elements within a given domain share a common identifier. See also DNS. Domain (BIND) Implementation of a DNS server developed and distributed by the University of California at Berkeley. Many Internet hosts run BIND, the ancestor of many commercial implementations. DOR Dial-optimized routing. DOS Disk Operating System. dot address The common notation for IP addresses of the form A.B.C.D; where each letter represents, in decimal, one byte of a 4-byte IP address. See also Class A/B/C address, IP address. dotted-decimal notation (1) The syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. Used to represent IP addresses in the Internet; for example, 192.67.67.20. (2) The syntactic representation of a MIB (management information base) object. download The transfer of a system, program, or file from a disk file at one node to the memory of another computer. The activity of loading software into the nodes of a network from one node or device over the network media. downstream
In any ring topology network, the direction of data flow. The downstream node is the next node to receive a frame or token. DR Designated router. Draft International Standard (DIS) A development step near final status on an ISO specification. DRAM Dynamic random access memory. Type of computer memory that stores electrical charges to represent memory states and requires continual recharging (refreshing). driver A software module that controls an input/output port or external device such as a keyboard or a monitor. TCP/IP uses a driver to control the network interface cards. drop cable A cable used to connect a station's AUI port to a transceiver; also called AUI cable, transceiver cable, or transceiver drop cable. DS0 Digital service, level 0. Common carrier digital transmission service at 64 Kb/s. DS1 Digital service, level 1. Common carrier digital transmission service at 1.544 Mb/s. Also known as T1. DS1E Digital service, level 1, E. DS3 Digital service, level 3. Common carrier digital transmission service at 44.736 Mb/s. Also known as T3. DSAP Destination service access point. An internal address of a specific software entity to which data must be delivered when it arrives at its destination, according to the IEEE 802.3 LLC (Logical Link Control) standard. This information may be included in the data field of an 802.3 transmission frame. DSL Digital Subscriber Line, also Loop. Modems on either end of a single twisted pair wire that delivers ISDN Basic Rate Access. See also ADSL, HDSL, RADSL, SDSL. DSP Digital signal processor. A specialized microprocessor that performs complex operations on digitized signals that were originally analog. Useful in processing sound and video. DSR Data set ready. A hardware signal defined by RS-232-C that indicates that a device is ready to operate. DSS Distributed Sniffer System. DSU Digital service unit or data service unit. A device connecting data terminal equipment (DTE) to digital communication lines that ensures that data to be transmitted across the network is formatted correctly.
DSX (T1) Digital System Cross-Connect switch. DSX1 Digital Signal Cross-Connect Level 1. DTE Data terminal equipment. Equipment that is a source or destination of transmitted data, such as a personal computer, workstation, server, bridge, router, gateway, terminal, or other device on the network; also called host, host device, node, or station. A DTE device typically connects to a data communication equipment (DCE) device. See also DCE. DTR Data terminal ready. A hardware signal defined by RS-232-C sent from a computer to an RS-232-compatible DCE device to indicate it is ready to receive a transmission. dual homing A method of connecting devices in which there is a primary connection and a standby connection. dual ring A pair of counter-rotating, logical rings. duplex cable Copper optical cable that consists of a transmit channel and a receive channel bundled together. DVMRP Distance Vector Multicast Routing Protocol. A protocol in the IP suite that allows a router to advertise shortest-path routes to multicasting source networks (networks containing hosts with the capability of issuing multicast datagrams). Each multicasting router periodically issues routing information on each DVMRP circuit, which represents the sum of the hop metrics along the shortest path from the router to the given source network. DXI Data exchange interface. SMDS Interest Group data exchange specification for interaction between internetworking devices transmitting over an SMDS access line. E1 Communications interface used in Europe that transmits at a data rate of 2.048 Mb/s. The European counterpart to T1. See also T1. E2 Communications interface used in Europe that operates at a data rate of 8.448 Mb/s. E3 Communications interface used in Europe that operates at a data rate of 34 Mb/s. E4 Communications interface used in Europe that operates at a data rate of 139.264 Mb/s. E-Carrier A family of digital trunking methods supported in Europe. The European counterpart to T-Carrier. See also T-Carrier.
E-mail Electronic mail. Applications allowing the sending of electronic messages from one computer to another. Features may include storing and forwarding of mail, enclosure of attachments. Also known as email; however, e-mail is the more common usage. EBCDIC Extended Binary Coded Decimal Interchange Code. A standard character-to-number code used by IBM computer systems. ECF Echo frame. A type of station management frame in FDDI that allows a station to perform loopback testing. echo test A diagnostic test in which a test packet is sent to elicit a standard response in order to check how far a network reaches. ECM Entity Coordination Management. Part of the FDDI station management specification. The ECM resides within the PHY sublayer and is responsible for the media interface to the FDDI network. ED End delimiter. Byte that marks the end of a frame in token ring and FDDI blocks. EDEL End delimiter field. EEPROM Electrically erasable programmable read-only memory. A memory that can be electronically programmed and erased but does not require a power source to retain data. EFS End of frame sequence. In FDDI frame and token format blocks, consists of ending delimiter (ED) and frame status (FS) fields. EG Electrotechnical Group. EGP Exterior Gateway Protocol. A protocol in the IP suite used to exchange network reachability information between routers in different autonomous systems. Routers establish EGP neighbor relationships in order to periodically exchange reliable reachability information. See also BGP. egress The point where an outbound data flow exits a system. See also ingress. EIA Electronic Industries Association. An industry trade organization that sets standards for consumer products and electric components. EIA RS-232 the Electronic Industries Association standard for the 25-pin serial interface used to connect personal computers or terminals (DTEs) to communications equipment, such as modems (DCEs). EIA/TIA-449 A joint standard of the Electronic Industries Association and the Telecommunications Industry Association, providing specifications for RS-449, the physical layer interface. See also RS-449.
EIA/TIA-568 A joint standard of the Electronic Industries Association and the Telecommunications Industry Association, providing specifications for unshielded twisted pair wiring and wire cabling for Ethernet, token ring, ISDN, and other networking systems. The current version is ANSI/TIA/EIA-568-A-1995. EIR Excessive Information Rate. Excess (higher than expected) traffic that can be accepted by a frame relay network if there is no other traffic congestion. See also CIR. EISA Extended Industry Standard Architecture. A common 32-bit data bus architecture used by the computer industry that allows more than one processor to share the bus. ELAN Emulated LAN. Following the ATM Forum Sub-working Group LAN Emulation specification, emulated LANs make connection-oriented ATM networks look like connectionless local area networks. ELAP EtherTalk Link Access Protocol. Part of the data link layer (layer 2) of Apple Computer's AppleTalk network protocol used to transmit packets between nodes on the same physical network. ELM Elasticity Buffer and Link Management. EMA Enterprise Management Architecture. Digital Equipment Corporation's network management scheme based on the ISO network management model. EMC Electromagnetic compatibility. The ability of equipment to be used in the intended environment within designed efficiency levels without causing or receiving degradation due to unintentional electromagnetic interference (EMI). EMI Electromagnetic interference. See EMC. EMT Embedded management tool. A board that gathers statistics and provides embedded core management when installed on a token ring host module, such as Bay Networks Model 559 embedded management tool. Emulated LAN (ELAN) Following the ATM Forum Sub-working Group LAN Emulation specification, emulated LANs make connection-oriented ATM networks look like connectionless local area networks. end point On an ATM network, an end station, server, or internetworking device connected to the network. End points utilize either a user-to-network interface (UNI) for end stations or servers or a network-to-network interface (NNI) for switch-to-switch connections. end-user device A physical device or collection of devices, such as workstations, servers, or printers, that are identified by a MAC or ATM address and connected to a virtual network. ENQ Enquiry character. A control character or byte that indicates an enquiry.
ENS Enterprise Network Services. Software product based on Banyan Systems' Directory Service for VINES that allows networks with other operating systems to use the VINES directory service. See also VINES. enterprise network A network that connects every computer in every location of an organization, often those running different operating systems and attached to different kinds of networks. EOF End of file. A control character or byte used to indicate that the last character of the last record of a file has been read. EOT End of transmission. A control character or byte in computer communications used to indicate the end of the message. Eprom or EPROM Erasable programmable read-only memory. UV light-reprogrammable memory chips that may contain only the special program originally electrically burned in. equipment room A central building or room where distribution cabling is switched and terminated and voice and data communications equipment are located; also called communications closet, telecommunications closet, or wiring closet. ER Explicit route. error rate The percentage or the ratio of errors to the total data packets received for the device. ESAF Ethernet sync adaptor with filter. ESETM Ethernet Switching Engine. A Bay Networks System 3000 Ethernet switching module that allows multiple parallel data exchanges to take place simultaneously with minimal latency. The ESE provides 10 Mb/s switching between the channel A and channel B backplane segments of the System 3000. ESF Extended service frame. A type of station management (SMT) frame in FDDI that allows a vendor to extend and create new SMT services. See also D4. ESIA Extended Sniffer Internetwork Analyzer. ES-IS End system to intermediate system. ESM Enterprise Server Module. The Model 5745 ESM is a high-performance, System 5000-based, channel-attached gateway that provides SNA-to-IP capabilities and Web browser access to IBM mainframes.
ET Exchange terminator. An ISDN device located at a phone company's central office, performing switching exchange functions. EtherCellTM Early Bay Networks Ethernet-to-ATM switches that perform high-speed data switching to connect Ethernet networks or end stations to ATM backbone networks. EtherExpress A 100 Mb/s Fast Ethernet adapter card sold by Intel Corporation. Ethernet Widely used LAN technology defined by the IEEE 802.3 specification. Ethernet networks run at a data rate of 10 Mb/s, 100 Mb/s, or 1000 Mb/s, using baseband transmission and CSMA/CD access on full duplex. The IEEE/ISO standard provides for integration into the OSI reference model and extends the physical layer and media with repeaters and implementations that operate on fiber optics, broadband, and unshielded twisted pair cable. See also CSMA/CD, LAN, topology. Ethernet adapter An expansion card that controls the exchange of data between a personal computer or other DTE and an Ethernet network; also called Ethernet card, network interface card, or NIC card. Ethernet address A 48-bit number usually expressed as a 12-digit hexadecimal number that uniquely identifies a workstation, server, or other device on a network. Ethernet Workgroup Switch (EWS) Part of the Bay Networks BayStack family, this 10BASE-T switch includes six 10 Mb/s ports with an optional 100 Mb/s MDA and provides a segmented dedicated 10 Mb/s path. The switch connects users on different segments without interfering with other network segments. EtherSpeed Bay Networks 16-port switch module for 10 Mb/s half- or full-duplex Ethernet networks over unshielded twisted pair cable. Part of the Centillion 100 family of switching products. ETR Early token release. Mechanism on a 16 Mb/s token ring network whereby a sending station appends a free token to its message so that a token is available before the single token completes its ring. ETSI European Telecommunication Standards Institute. The European counterpart to ANSI, and coordinating with ITU. See also ANSI, ITU. http://www.etsi.org/ Expanded View Part of the Bay Networks Optivity software. A device-configuration tool that graphically depicts all components of a hub in real time in one window and allows remote configuration of the hub. expansion cable Cable used to connect concentrators in a cluster through their expansion ports. expansion port A port on a Bay Networks switch that enables direct connection to another switch unit or transceiver. external crossover A wiring crossover that reverses the transmit and receive wire pairs in a UTP cable.
external transceiver a separate transceiver (equivalent to an IEEE 802.3 MAU), typically connected to the AUI port of an Ethernet network interface card. Extranet A method, using the Internet, by which remote users and multiple LANs can be connected to a corporate intranet. See also tunneling, VPN. Extranet Switches Bay Networks products supporting manageable, scalable access with high security and predictable bandwidth to connect remote users to an intranet via a public network. See also ContivityTM Extranet Switch, tunneling, VPN. EZ InstallTM A Bay Networks application that allows you to boot and configure new hubs automatically from the network management station. EZ InternetworkTM Bay Networks workgroup network management software based on Microsoft® Windows® and designed for configuring Bay Networks routers and for monitoring and managing Bay Networks and other MIB-II-compliant routers. EZ LANTM Bay Networks workgroup network management software based on Microsoft Windows that automatically recognizes any device on the managed network and defines the relationship of the device to other network devices in real time. Fast Ethernet 100BASE-T, IEEE 802.3u Ethernet specification for 100 Mb/s transmissions over unshielded twisted pair or fiber optic cable. FastLinkTM Bay Networks client access software supporting remote nodes and remote node applications. FastMatrixTM An early Bay Networks ATM switching architecture for high-speed switching, such as for the Model 5000AH Switching Hub. FAT File allocation table. FaultManTM Bay Networks UNIX application that works with Optivity to detect network faults automatically and alert the network manager. Evaluates and groups associated traps to reduce the amount of data. fault management One of the five network management application areas defined by ISO; concerned with detecting, isolating, and correcting abnormal network operation. See also network management, ISO. fault tolerance The ability of a program or system to operate properly even when a fault occurs. Fault-tolerant systems are designed to ensure that even in the event of a power failure, a disk crash, or a major user error, for example, data is not lost and the system can continue operation. FBM Frame-based management. Station management (SMT) services provided by specific frame types in FDDI.
FC Frame control. The third byte in a token ring frame. Contains information from the LLC or MAC sublayers. FCC Federal Communications Commission. U.S. government regulatory body for radio, television, and interstate telecommunications services and international services originating in the United States. FCS Frame check sequence. The error check on a frame. In an FDDI and token ring block, FCS detects erroneous data bits within the frame via a 32-bit cyclic redundancy check. FDDI Fiber Distributed Data Interface. A specification developed by ANSI and IEEE for high-performance fiber optic networks operating on two counter-rotating rings at 100 Mb/s. FDL Facility data link. FDM Frequency division multiplexing. Networking process where the total capacity of the medium is divided into multiple, independent bandwidth channels. FDX Full duplex. The ability for communications to flow both ways over a communications link at the same time. FE Framing error. FECN Forward explicit congestion notification. Bits within a frame header in a frame relay system used to indicate congestion in the path in the same direction as the frame is flowing. feeder link The link that connects feeder ports on modular and switching hubs. The feeder link carries traffic for a single virtual LAN. When a feeder link is used to connect two switches, only the network traffic is carried between the two switches (the connected switches do not share global station MAC address information). feeder port An expansion port or attachment port of a switch that connects to a host, a hub, or a repeater. FEP Front-end processor. Specialized processor that manipulates data before passing it on to the main processor. IBM SNA networks use these computers to handle addressing for host mainframes. FERF Far-end receive failure. Remote fault signal in a fiber optic network indicating that a port is not receiving light at the receive fiber. fiber A filament-shaped optical waveguide made of dielectric materials, typically a strand of glass. fiber optic cable A cable containing one or more optical fibers, specifically for data transmission. Thin, transparent fibers of glass or plastic that transmit light.
FID Format identification. FIFO First in first out. A storage retrieval method or buffering scheme in which the data that enters the buffer or storage media first is the first to be retrieved. Contrast to LIFO (last in first out). file transfer The copying of a file from one computer to another over a computer network. See also FTP. filtering The process of examining a data packet on the network and determining the destination of the data to decide whether the packet should be passed along on the local LAN, copied to another LAN, or dropped. Performed by bridges, switches, and routers, filtering is the decision not to forward a packet or how to forward it (for example by specifying a subset of destination addresses). Flatnet flat network. A network bound by routers. flow control A method used for controlling the transfer of data between two points on a data network that avoids data loss when the receiving device buffer is full. In Bay Networks modular and Fast Ethernet switches, a feature used on 100 Mb/s full-duplex links to control traffic and avoid congestion on the link. If the receive port buffer becomes full, the switch issues a flow-control signal to the device at the other end of the link to suspend transmission. When the receive buffer is no longer full, the switch issues a signal to resume the transmission. FLP burst Fast link pulse burst. A burst of 100BASE-T link test pulses that encapsulate autonegotiation information for identifying the speed and mode at which a device operates. FM Frequency modulation. FMD Function management data. FNTM Feeder Node. An early Bay Networks multiprotocol router with up to four LAN/WAN interfaces. FOIRL Fiber optic inter-repeater link. An obsolete fiber optic cable implementation of the IEEE 802.3 standard between repeaters, now superseded by 10BASE-FL. See also 10BASE-FL. FOMAU Fiber optic medium attachment unit. An IEEE 802.3 medium attachment unit that uses a fiber optic medium. forwarding table A table that contains station IDs and addresses and limits forwarding to specific addresses and address ranges. FPGA Field programmable gate array.
FPS Fast packet switching. FPU Frame processing unit. A device used to recognize and analyze various network frames in order to gather network statistics. FR Frame relay. A high-speed, packet-switching WAN protocol, designed to provide efficient, high-speed frame or packet transmission with minimum delay. Frame relay uses minimal error detection and relies on higher-level protocols for error control. FRAD Frame Relay Access Device. Unit(s) providing connectivity to a frame relay network for non-frame relay devices. fragment (1) Smaller piece into which a packet can be divided to fit the physical requirements of the network. It is reassembled at the destination. (2) A piece of a packet resulting from a collision of packets on the same LAN medium or segment. fragmentation The process in which a packet or IP datagram is broken into smaller pieces to fit the requirements of a physical network over which the packet must pass. The reverse process is termed reassembly. frame A unit of data transmission in a local area network, usually Ethernet or token ring. A frame normally includes delimiters, control characters, information, addresses, and checking characters (destination address, source address, length field, data, PAD, and a frame check sequence). The 802.3 standard specifies that the minimum size data frame is 64 bytes and the maximum is 1518 bytes. Frames are OSI layer 2 protocol data units. frame relay A high-speed, packet-switching WAN protocol, designed to provide efficient, high-speed frame or packet transmission with minimum delay. Frame relay uses minimal error detection and relies on higher-level protocols for error control. Frame Relay Forum An association of corporate members including vendors, carriers, users, and consultants committed to the implementation of frame relay in accordance with national and international standards. http://www.frforum.com/ frame switch A device that provides an OSI layer 2 frame-forwarding function between ports so that Ethernet or token ring LAN frames are directed across the network to the addressed end station. In the context of a structured network, a frame switch enables an administrator to rearrange wiring closet, server, and router virtual workgroup relationships as departments move or as network resources are added. Frame-switched segments are combined into logical networks. FRE® Fast Routing Engine. A 32 MHz processor used with Bay Networks Intelligent Link modules. FRE-2 Fast Routing Engine. A 32 MHz or 60 MHz processor module used with Bay Networks Intelligent Link modules to increase the speed of processing in BLN and BCN routers.
FRMR Frame reject. FRSw Frame Relay Switch. See also frame relay. FRU Field replaceable unit. FS Frame status. In FDDI and token-ring blocks, a minimum of three control-indicator symbols that indicate if the addressed station has recognized its address, the frame has been copied, or any station contains an error in the frame. FSI FDDI System Interface. FSMA Field-installable subminiature assembly. A type of threaded connector for fiber optic cable called out in the 802.3 FOIRL specification. FSP File Service Protocol. A file transfer protocol, similar to FTP except that it does not create much load on a server. FTAM File Transfer, Access, and Management. An application layer communications protocol for transferring files between systems of different vendors. FTP File Transfer Protocol. Protocol that allows a user on one host to access and transfer files to and from another host over a network. Defined in STD9, RFC 959. In LAN technology, a file-sharing protocol that operates at layers 5 through 7 of the OSI reference model. On the Internet, a tool for accessing linked files. GAME Gate Access Management Entity. Operating system in Bay Networks Backbone Node and Access Stack Node platforms. gate array A standard chip containing a series of logic gates and mathematical functions (transistors). The chip can be customized to allow a quick, inexpensive prototype of an electronic system. gateway (1) A device that converts the protocols and conventions of one network to those of another, for instance, between a personal computer network and a mainframe. (2) A device that forwards traffic between networks, based on network layer information and routing tables, now known as a router. GB Gigabyte. A unit of measurement equal to 1024 (210) megabytes. One billion bytes. Gb Gigabit. 109 = 1,000,000,000 (1 billion) bits.
Gb/s Gigabits per second. A unit of data transmission rate of 1,000,000,000 bits per second, or 1,000 megabits per second. GEM Global Enterprise Management. Bay Networks UNIX-based network management application. See also AssetManagerTM, Vision DesktopTM. GetNextRequest Command used by an SNMP manager to retrieve data in a table of objects. GetRequest is used to retrieve the first value, and GetNextRequest is used to request subsequent values. GetRequest Command used by an SNMP manager to retrieve information from an SNMP agent. GetResponse Command used by an SNMP agent to send data back to an SNMP manager. GFC Generic flow control. The first four bits of an ATM cell header. Manages traffic flow to the ATM network by controlling the user-network interface (UNI). GGP Gateway-to-Gateway Protocol. The protocol core gateways used to exchange routing information, implementing a distributed shortest path routing computation. GHz Gigahertz. One billion cycles per second. Gigabit Ethernet Data transmission on Ethernet networks at speeds of 1,000,000,000 b/s (1000 Mb/s or 1 Gb/s). Existing Ethernet networks can be upgraded to Gigabit Ethernet in order to provide increased bandwidth and traffic capacity. IEEE standard, 802.3z, addresses various parameters specific to Gigabit Ethernet. See also 802.3z, IEEE. Gigabit Ethernet Alliance An open forum promoting industry cooperation in the development and standardization of Gigabit Ethernet technology. http://www.gigabit-ethernet.org/alliance/ GIGArrayTM The interlinking of up to 16 Bay Networks Centillion 100 switching devices for automatic load-balancing across multiple ATM backbone links. GMII Gigabit Media Independent Interface. A standardized interface within the 802.3 Gigabit Ethernet standard. See also 802.3z. GMT Greenwich mean time. GOSIP Government Open Systems Interconnection Protocol. Set of standards based on the OSI reference model for use in government projects.
GRE Generic Routing Encapsulation. A protocol providing data encapsulation to allow tunneling. Growth bytes Unused SONET Line Overhead bytes, reserved for future functions not yet defined by SONET standards. Growth bytes are positioned as the first two bytes of the last row of a SONET frame. GUI Graphical User Interface. Computer interface method where the user performs various functions by pointing to graphic icons on the screen instead of typing in a string of commands. H.320 An ITU-T standard addressing videotelephony specifications over ISDN and other circuit switched networks and services. See also ITU-T. H.323 An ITU-T standard, an extension of H.320, addressing audiovisual communication on LANs, including corporate intranets and packet-switched networks. See also ITU-T. H.324 An ITU-T standard addressing High Quality Video and Audio Compression over POTS modems. See also ITU-T. H-channels ISDN high-speed bearer channels. half duplex Alternating transmissions over a communications link. Each station can either transmit or receive, but cannot do both simultaneously. HDB3 High-density bipolar coding. HDLC High-level Data Link Control. A bit-oriented (physical) data link protocol developed by ISO for full-duplex communications. HDCM Harpoon Diagnostic Console Monitor. A BN function allowing various reset commands, primarily for the FRE module. HDSL High data rate Digital Subscriber Line. Modems on either end of one or more twisted pair wires that deliver T1 or E1 speeds. header The first part of a packet, frame, or cell preceding the message data and trailer; the header carries special information used by the network to the destination station. For example, in ATM networks, cell header information pertains to ATM layer functionality, mainly the identification of cells by means of a label. The header in an ATM cell is made up of 5 bytes of information. HEC Header error control. The last byte of an ATM cell header. Guards against the misdelivery of cells due to header or single bit errors.
hierarchical backbone A backbone with more than one layer in the overall network architecture. Each layer can be either distributed or collapsed. hierarchical star topology Network topology in which groups of stations are connected to a concentrator and groups of concentrators are in turn connected to a higher-level concentrator. hop A unit of measurement indicating the passage of a packet through one router or bridge. hop count The number of routers and bridges a packet traverses between a source and destination. A header field in the packet stores the hop count. Each router or bridge in the path drops the packet if the hop count exceeds a predetermined value and adds one to the hop count if it does not. horizontal cable The wiring in place between the telecommunications outlet in the workspace and the wiring closet on the user's premises. host, host device A personal computer, workstation, server, or other device connected to a network at a single point that allows the user to communicate with other host computers on a network. Individual users communicate by using application programs such as electronic mail, Telnet, and FTP; also called data terminal equipment, DTE, node, or station. host module A module installed in a chassis, concentrator, or hub that accepts cabling of a particular medium type (such as fiber optic, shielded twisted pair) from host devices to connect user stations on a network. Each medium access type (Ethernet, token ring, or FDDI) has its own host module. host name A name that a system administrator assigns to a system unit to uniquely identify it for users. host number The host part of an Internet address, the remaining portion of the address being the network number. Internet Protocol (IP) hosts encode numbers in dotted-decimal notation, which uniquely identifies a system unit for a network. hot-swap The process of removing and replacing a module or subassembly in a powered-on electronic device without disrupting network communication on other components. HPR High Performance Routing. An APPN enhancement that includes Automatic Network Routing (ANR) and the Rapid Transport Protocol (RTP). See also ANR, RTP. HSSI High Speed Serial Interface. High-level serial interface supporting up to 52 Mb/s and offering LAN-like performance over a wide area. http Hypertext Transfer Protocol. A client/server protocol for linking text files to one another to share information on the Internet and the World Wide Web (WWW).
hub A physical layer device, connected to other devices, that restores a signal's amplitude and timing for transfer across a network. Known as a repeater in most IEEE 802.3 standards and also called a concentrator. The hub usually resides at the core of a star topology network and is used for the transfer of messages. Hubs provide Ethernet, token ring, and/or FDDI functions; accept host, internetworking, and network management modules; and provide retiming/repeater, bridging, and/or network management functionality. A typical hub has multiple user ports to which computers and peripheral devices are attached. See also topology. hybrid cable A communications cable containing two or more types of conductors carrying electric signals, a mix of conductors and optical fibers, and/or two or more kinds of optical fiber. A cable containing signal-bearing media and electric power conductors. hybrid switch A switch with a mixture of frame-based and cell-based external interfaces. Hybrid switches provide translation between the frame domain and cell domain internally. I2O SIG Intelligent Input/Output (I/O) Special Interest Group. A group of leading enterprise vendors defining a technical specification as a standard interface for high-performance I/O systems. http://www.i2osig.org/ IAB Internet Architecture Board. A technical advisory group of the Internet Society, providing oversight of the standards development for protocols and procedures used by the Internet. See also IETF, ISOC. http://www.iab.org/iab/ IBM Cabling System the 150-ohm impedance shielded twisted pair premises wiring systems sold by International Business Machines (IBM) Corporation. IBM data connector A four-position connector used in the IBM Cabling System. IBNM In-band Network Management. ICMP Internet Control Message Protocol. Extension to the Internet Protocol (IP) that allows for generation of error messages, test packets, and informational messages related to IP. icon A graphic symbol on a user interface display. ICP Internet Control Protocol. Protocol that tracks the internet address of nodes, routes outgoing messages, and recognizes incoming messages. IDF Intermediate distribution frame. A metal rack for cable connections located in an equipment room or closet. Provides the connection between the main distribution frame (MDF) and individual phone wiring. IDP Internetwork Datagram Protocol.
IEEE Institute of Electrical and Electronics Engineers. Professional organization that acts as a coordinating body for electrical, electronic, computing, and communications standards. It ensures that systems from different manufacturers communicate with minimum adjustments, enabling a device from one vendor to exchange messages with devices from other vendors. http://www.ieee.org/ IEEE 802 IEEE standards developed by an IEEE subcommittee specifically addressing LAN/MAN standards such as Ethernet, token ring, and various LAN configurations. http://grouper.ieee.org/groups/802/index.html IEEE 802.2 The IEEE standard that specifies the link layer control (LLC) portion of the data link layer (DLL) for various media access methods. See also DLL, LLC. IEEE 802.3 the IEEE standard for Ethernet networks; in full, ANSI/IEEE Standard 802.3. It includes rules for configuring Ethernet LANs, the types of media that can be used, and how the elements of the network should interact. http://grouper.ieee.org/groups/802/3/index.html IEEE 802.5 the IEEE standard for token ring networks. Covers rules for configuring token ring LANs, the types of media that can be used, and how the elements of the network should interact. IETF Internet Engineering Task Force. An international group of network professionals and vendors providing technical contributions to the engineering and evolution of the Internet, with oversight by the Internet Architecture Board (IAB). See also IAB. http://www.ietf.org/ I-Frame Information frame. IFTF Interframe time fill. IGMP Internet Group Management Protocol. A protocol in the IP suite that allows a host to register its local network with the local router to receive any datagrams sent to that router and targeted to a group with a specific IP multicast address. Bay Networks routers support IGMP version 2. IGP Interior Gateway Protocol. Term applied to any protocol used to increase network reachability and distribute routing information within an autonomous system. Routing Information Protocol (RIP) and Open Shortest Path First (OSPF) protocols are common IGPs. See also OSPF, RIP. IGRP Interior Gateway Routing Protocol. Proprietary protocol used by Cisco Systems. IHL Internet header length.
IISP Interim Inter-switch Signaling Protocol. A standardized signaling protocol to enable switched virtual circuits (SVCs) between switches in a private ATM network using static routes. Based on UNI 3.1 with optional support for UNI 3.0. ILACC Integrated local area communications controller. ILEC Incumbent Local Exchange Carrier. Established, formerly regulated telecommunications companies. ILI Intelligent Link Interface. A link module and processor board pair that receives packets or frames, then bridges, routes, switches, or filters them. ILIs fit into Bay Networks Backbone Node hardware platforms and exchange traffic and data over a 2- or 4-way bus called a Packet Parallel Express (PPXTM). ILMI Interim Local Management Interface. An ATM Forum signaling and addressing protocol. IMS Information Management System. An IBM hierarchical database management system for mainframes. IMTC Interactive Multimedia Teleconferencing Consortium. Nonprofit corporation involved in the development and implementation of multimedia teleconferencing issues, based upon international standards, primarily those developed by the ITU. See also ITU, VoIP Forum. http://www.imtc.org/ IN Integrated node. in-band signaling The transmission of signaling information at some frequency or frequencies that lie within a carrier channel normally used for information transmission. indicator A light in a display, often an LED. The state of the light indicates information about the device to which it is attached. industry standard architecture Expansion bus commonly used in PCs that controls peripheral components. ingress The point where inbound data flows enter a system. See also egress. INTAP Interoperability Technology Association for Information Processing. intelligent hub Manageable hub, meaning that each port on the hub can be configured, monitored, and enabled or disabled by a network operator from a hub management console. Hub management can also include processing functions and information gathering of network parameters such as the number or types of transmitted packets, the number of errors, or the number of collisions. See also manageable hub, active hub, passive hub.
interconnect module A network module that provides a single-channel connection from a local concentrator to a central concentrator. internal crossover A crossover implemented through internal circuitry in a device. internal transceiver A transceiver (equivalent to an IEEE 802.3 MAU) implemented as part of the internal circuitry of an Ethernet network interface card; also called onboard transceiver. International Consultative Committee for Telegraphy and Telephony (CCITT) Now ITU-T; International Telecommunication Union-Telecommunications sector. See also ITU, ITU-T. International Organization for Standardization (ISO) A worldwide voluntary federation of national standards organizations, founded in 1946, responsible for creating international standards in many areas, including computers and communications. Members are the national standards organizations of member countries, including ANSI for the United States. Known in networking for its Open Systems Interconnection (OSI) seven-layer reference model, which specifies how dissimilar computing devices such as network interface cards, bridges, and routers exchange data over a network. See also OSI. http://www.iso.ch/welcome.html Internet A computer network that joins many government and university and private computers together over phone lines (mostly T1s and T3s), serving organizations such as the National Science Foundation and Advanced Research Projects Agency. The worldwide Internet that has evolved from the network developed as the U.S. Department of Defense Advanced Research Projects Agency (DARPA) Internet and the TCP/IP Transmission Control Protocol (TCP) and Internet Protocol (IP) it uses. See also IP, TCP. Internet address A 32-bit Internet Protocol (IP) source or destination address. See also Class A/B/C address, IP address. internetwork A collection of two or more packet-switching networks that may be dissimilar, interconnected by routers that allow them to function logically as a single, large network. internetworking (1) Linking individual local area networks together to form a single internetwork. Sometimes called an enterprise network because it interconnects computer networks throughout the entire enterprise. (2) A method of linking hubs by repeating all packets from one hub to the other hub. internetworking modules Modules (or standalone units), such as bridges or routers, that connect individual local area networks together. interoperability The ability of software and hardware on multiple machines from multiple vendors to communicate successfully. intranet A private corporate network providing Internet-like functions and applications to internal users. Occasionally referred to as intranetwork. See also Extranet. invalid cell A cell where the header is declared by the header error control (HEC) process to contain errors.
inverted backbone A distributed backbone that uses a local area network for the backbone but is physically contained in a small area, such as an equipment room. Most common in token ring environments where two-port bridges are connected to a backbone 16 Mb/s ring in the computer room. inverted tree topology the topology used by computer networks, in which groups of stations are connected to a central concentrator, like branches of a tree, and the concentrators at the centers of these branches are in turn connected to a higher-level concentrator in a tree; also called hierarchical star topology. I/O Input/output (interface). Transferring data and control information between a CPU and a peripheral device. IP Internet Protocol. Part of the TCP/IP suite of protocols defined in RFC 791. Describes the software responsible for routing packets and addressing devices.The standard is used for sending the basic unit of data, an IP datagram, through an internetwork. Provides an unreliable, connectionless data delivery service on a "best-effort" basis. IP address Internet Protocol address. The 32-bit (4 byte) address, defined by the Internet Protocol in STD 5, RFC 791, used to represent a point of attachment in a TCP/IP internetwork. An IP address consists of a network portion and a host portion to make routing more efficient. It is usually represented in dotted-decimal notation. See also Class A/B/C address, dot address, network address, subnet address. IPC Interprocess Communication Protocol. The exchange of data between one program and another within the same computer or over a network. A protocol that guarantees a response to a request. IPCP Internet Protocol Control Packet. Specialized IP over PPP network control protocol packet. IPEX Internet Protocol Encapsulation of X.25. IPG Interpacket gap. An idle period between two packets in the IEEE 802.3 standard. IP Multicast Standard IETF communications protocols addressing multimedia data transmission over the Internet, as well as via other communications services and networks. See also IETF. IP Multicast Initiative An international, multivendor forum accelerating the adoption of the IETF IP Multicast standard. http://www.ipmulticast.com/ IPNNI Integrated Private Network-to-Network Interface. An emerging multiple link state protocol, being developed as an extension to the PNNI ATM routing protocol. It will be used for effective route determination and distribution in hybrid LAN/ATM internetworks.
IPsec Internet Protocol Security. An emerging standard, this Bay Networks supported tunneling protocol offers strong encryption, support for IP address translation, and packet-by-packet authentication. Special ISP services are not required. IPX Internetwork Packet Exchange. The Novell NetWare protocol that provides datagram delivery of messages. IPX facilitates communications between end stations on geographically dispersed LANs supporting a large range of applications and provides the network layer functions of addressing and routing to facilitate communications between a client and a NetWare server. IPXCP Internetwork Packet Exchange Control Protocol. IPXWAN Internet Packet Exchange Wide Area Network. Novell NetWare specification/protocol. IR Internetwork router. ISA Industry standard architecture. An expansion bus commonly used in PCs that accepts the plug-in boards that control video display, disks, and other peripherals. Most PC expansion boards on the market are ISA. ISDN Integrated Services Digital Network. An international telecommunications network, based on a set of communications standards, for digital transmission of voice, video, and data over WANs. ISDN interfaces also provide LAN connections and remote access capability. ISDN has two types of service: BRI (basic rate interface) and PRI (primary rate interface). See also BRI, PRI. ISDN BRI Integrated Services Digital Network basic rate interface. See BRI. ISDN PRI Integrated Services Digital Network primary rate interface. See PRI. IS-IS Intermediate System to Intermediate System. ISN Initial sequence number. ISO International Organization for Standardization. A voluntary federation of international standards organizations, founded in 1946, responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of member countries, including ANSI for the United States. Known in networking for its Open Systems Interconnection (OSI) seven-layer reference model, which specifies how dissimilar computing devices such as network interface cards, bridges, and routers exchange data over a network. See also OSI. http://www.iso.ch/welcome.html ISO Reference Model for OSI International Organization for Standardization reference model (ISO 7498:1984) for Open Systems Interconnection. A standard modular approach to network design that divides a complex set of functions into functional layers. Starting from the innermost layer, these layers are: physical, link, network, transport, session, presentation, and application.
ISO 8802-3 An international standard that represents ANSI/IEEE 802.3. ISOC Internet Society. A nonprofit, international organization focusing on Internet standards, education, and policy issues. http://info.isoc.org/index.html isochronous Signals that are dependent on some uniform timing or carry their own timing information embedded as part of the signal. isolated board A board that is not connected to a backplane segment or ring. isolated cluster A host module cluster that is not connected to a backplane segment or ring. isolated ring In a token ring hub, a module-level ring that is not associated with a backplane ring. Only one cluster can operate on an isolated ring. isolated segment A segment within a hub or concentrator that does not connect to any other segment, either locally or through the chassis backplane. ISP Internet service provider. A company that provides users with a network connection to the Internet through SLIP or PPP connections to enable end users to run software such as a Web browser on their PCs or workstations. ISR Interrupt service routine. Routine that processes a service interrupt before returning control to the suspended process. ITU International Telecommunication Union. United Nations organization that develops and standardizes worldwide telecommunications. http://www.itu.ch/ ITU-T International Telecommunication Union-Telecommunications sector. International organization that defines standards for telegraphic and telephone equipment, having replaced the CCITT as the leading telecommunications standards organization. IWU Intermediate working unit. J1 Communication interface used in Japan that operates at a data rate of 1.544 Mb/s, equivalent to DS1 data rate. See also DS1, T1. jabber (1) Under the IEEE 802.3 Ethernet standard, a data packet whose length greatly exceeds specification. (2) An error condition where a station erroneously and continuously transmits. jack A receptacle into which a plug is inserted to make electrical contact.
JCL Job Control Language. JEMA Japan Electronic Messaging Association. JES Job Entry Subsystem. An IBM control protocol and procedure. jitter Short-term instabilities in network signal timing. JPEG Joint Photographic Experts Group. A graphic (still) image compression standard based on the way the human eye perceives color. See also MPEG. jumper A short wire connection between two points on a circuit board or wiring terminal strip implemented either by means of a modular connector or a hard-wired connection. JUNET Japan UNIX Network. K56flex A Rockwell/Lucent proprietary implementation of the 56 Kb/s ITU V.90 standard. Bay Networks Versalar Remote Access Concentrators (RAC) have K56flex capability. See also ITU, RACTM, V.90. kB Kilobaud. 1,000 bits of data per second. Stated as a modem's transmission speed for data rates, such as 19.6 kB. See also baud. Kb Kilobit(s). 103 = 1,000 bits. KB Kilobyte(s). 210 = 1,024 bytes. kHz Kilohertz. One thousand hertz or one thousand cycles per second . L2F Layer 2 Forwarding. A tunneling protocol enabling remote access to corporate networks across the public Internet. See also Extranet, VPN. L2TP Layer 2 Tunneling Protocol. A standards-based protocol providing remote users with dial-in access to a corporate network, via an existing ISP network. See also Extranet, VLAN. LAC L2TP Access Concentrator. Remote access equipment residing at an ISP network, establishing L2TP tunnels between itself and a router at the corporate network. See also LNS, VPN.
LAN Local area network. A communications network serving users within a limited geographical area, such as one floor of a building, controlled by a network operating system and using a transport protocol. User devices attached to a LAN include workstations, servers, and printers. Most local area networks employ the Ethernet, token ring, or FDDI access methods, or some combination of these. Several LANs can be interconnected to extend connectivity. See also Ethernet, FDDI, token ring, WAN. LANarchitectTM A Bay Networks Optivity application that graphically depicts a logical representation of virtual LANs for LattisSwitch hubs or workgroups for System 5000 or BayStack hubs. LANCE Local Area Network Controller for Ethernet. A very large scale integration (VLSI) device developed by AMD that provides data link functions for Ethernet controllers. LANE LAN emulation. The method used by switching equipment to emulate the characteristics of shared-media LANs, standardized by the ATM Forum to allow transparent operation of existing LANs and protocols across ATM. Facilitates the operation of broadcast-oriented, connectionless networks and employs a server to resolve addresses between Ethernet and ATM systems. Allows for multicast services for supporting broadcast traffic when needed and MAC driver interfaces in ATM stations, supporting existing protocols such as IP, APPN, NetBIOS, and IPX. LAN segment A portion of a local area network separated from other portions of the LAN by one or more bridges, routers, repeaters, or switches. Segmentation is generally enabled by individual ports on the same device, usually a switch. LAP Link Access Protocol. The link level elements used for data interchange between data circuit-termination equipment and data terminal equipment. A family of error correction protocols used on X.25 packet networks. See also LAPB. LAPB Link Access Procedure Balanced or Link Access Protocol Balanced. A protocol used for accessing an X.25 network at the link level. X.25 also specifies a LAP, or link access procedure (not balanced). Both LAP and LAPB are full-duplex, point-to-point bit-synchronous protocols. See also LAP. LAPD Link Access Procedure Digital, Link Access Protocol Digital, or Link Access Process Data. Link-level protocol devised for ISDN connections. LAT Local area transport. A communications protocol from Digital Equipment Corporation for controlling terminal traffic in a DECnet environment. LATA Local Access Transport Area. A service area within which (telephone) calling services are provided by a telephone company. late collision A collision occurring after the normal collision window of 72 bytes. Late collisions may indicate chattering transceivers, defective interface cards, defective network software or hardware, mismatched equipment, an oversized network, or other problems.
latency The time interval between when a network station seeks access to the channel and when transmission is received. LattisCellTM switches An early Bay Networks family of System 10000 nonmodular high-performance ATM switching hubs. LattisEngineTM An early Bay Networks network utility server. A hardware product that resides in a System 3000 chassis. LattisHubTM Bay Networks Model 28xx 10BASE-T hub, capable of network management. LattisLinkTM Bay Networks Model 28xx Ethernet hub, not capable of network management. LattisNet® Manager Early Bay Networks network management applications. LattisRingTM Bay Networks System 27xx token ring hub. LattisSecure® Early Bay Networks MAC layer filtering and security functionality resident on a Model 3368 Ethernet Host Module. LattisSecure modules provide a level of network security not ordinarily available with Ethernet and reside in a System 3000 chassis. See also BaySecureTM. LattisSpanTM An early Bay Networks protocol used between modular and Fast Ethernet switches and other Bay Networks switches, a variation of the IEEE 802.1d Spanning Tree Algorithm used by many bridges. LattisSwitchTM Early Bay Networks Ethernet switching hubs that provide accelerated performance and switched connectivity in both 10 Mb/s and 100 Mb/s networks. LattisSwitch hubs deliver 2 Gb/s of internal switching capacity. LattisTalkTM Early Bay Networks products supported by AppleTalk. LattisViewsTM An early Bay Networks software application that enabled users to manage Bay Networks Ethernet and token ring networking equipment from a number of integrated enterprise management systems. LattisWareTM Early Bay Networks DOS network management applications. layer A logically distinct level in network architecture. Communication networks are organized as a set of more or less independent protocols, each in a different layer; the lowest layer governs direct host-to-host communication between hardware at different hosts, and the highest layer consists of user applications. Each layer builds on the layer beneath it using protocols appropriate to the layer. TCP/IP has five layers of
protocols; OSI has seven. The methods of passing information from one layer to another are specified as part of the protocol suite, and changes within a protocol layer do not affect the other layers. LBC Line byte count. LCF-PMD Low-cost fiber-physical medium dependent. An FDDI standard developed by the ANSI X3T9 Committee that allows FDDI transmissions over lower-cost, optic fiber medium. LCN Logical channel number. LCP Link Control Protocol. LCT Link confidence test. LDAP Lightweight Directory Access Protocol. An IEEE protocol for accessing certain online services such as searching directories over TCP/IP. LE ARP LAN Emulation Address Resolution Protocol. leased line A private transmission line reserved for the leasing customer's sole use. LEC LAN emulation client. Ethernet port in a virtual LAN network that has its own ATM address. LECS LAN emulation configuration server. Portion of ATM Multicast Server (MCS) software that maintains tables of information such as virtual LAN membership and addresses. LED Light emitting diode. A semiconductor light source that emits visible light or invisible infrared radiation. LEM Link error monitor (or monitoring). Part of the physical sublayer of FDDI concentrator ports that examines the link error rate of an active link. LER Link error rate. The rate at which errors occur on an active link. LES LAN emulation server. Portion of ATM multicast server (MCS) software that provides LAN Emulation Address Resolution Protocol for a virtual LAN. link an electrical or fiber optic connection between a network station and a concentrator or between two concentrators.
linking hubs Because each hub usually represents a single LAN, interconnecting the LANs can be accomplished by an interrepeater or cascaded segment, which repeats all packets from one hub to the hub to which it is linked. link integrity test the 10BASE-T test for link continuity, in which ports monitor the link for either data or link test pulses. link LED An indicator that the cable from the station network adapter card to the host module is correctly installed and connected to an operating station. See also LED. link module A circuit board that fits into a slot in the rear panel of a Bay Networks Backbone Node platform. It provides the connection between a network cable and a Fast Routing Engine processor board. See also ILI. LinkSafeTM An Accelar 1000 series feature allowing a redundant fiber path between 2 Gigabit Ethernet ports. link state routing protocol A protocol, such as OSPF, that allows routers to exchange data regarding accessibility of other networks. Link state protocols exchange information only in response to topology changes. Distance vector protocols, such as RIP, exchange data periodically. See also distance vector protocol, OSPF, RIP. link station An APPN logical connection between adjacent nodes, with configurable parameters to identify and define the various nodes. link status the state of integrity of a physical or logical link in a network. link test pulse a 100 ns pulse transmitted as an idle signal over a 10BASE-T circuit every 16 ms in the absence of data. See also FLP burst. LLAP Local TalkLink Access Protocol. LLC Logical link control. In 802.x LANs, the 802.2 sublayer of the OSI reference model data link layer that provides data repackaging functions for operation between different network types; complements the media access control (MAC) sublayer. See also IEEE 802, DLL, MAC. LMI Local Management Interface. LN® Link Node. An early Bay Networks multiprotocol router with up to 16 LAN/WAN interfaces. LNM LAN Network Manager. LNS L2TP Network Server. A router that resides at the corporate network and serves as the termination point for L2TP tunnels and sessions. See also LAC, VPN.
lobe In a token ring network, the section of cable that attaches a network device to an access unit. lobe cable A cable that connects token ring stations to the concentrator. Lobe cables include the patch cables to wall outlets, horizontal distribution cables, and patch cables in the wiring closet between the patch panel and the concentrator. local segment A segment directly attached to a hub or other LAN interface device. LOF Loss of frame. logical network A network diagram created independent of physical device location that may include groups spread out over different locations (such as floors or even separate buildings). logical signaling channel A logical channel for signaling information that is contained within an information channel or a physical signaling channel. LOH Line Overhead, associated with SONET frames. LOP Loss of pointer. LOS Loss of signal. LQM Link Quality Monitoring. A Point to Point Protocol (PPP) function that checks the percentage of packets received versus packets sent on each end of a link. LQR Link Quality Report. Packets containing counters of incoming and outgoing data so that Point to Point Protocol (PPP) can calculate link quality. LRM Line Resource Manager. LSA Link state advertisement. LSB Least significant bit or least significant byte. The portion of a number, address, or field that occurs farthest right when its value is written as a single number in conventional hexadecimal or binary notation. The part of the number having the least value. LSD Least significant digit.
LSDV Link segment delay value. Value used in calculating the overall round-trip collision delay of an Ethernet network. This value is the delay value of the segment itself and does not include the delay values of the DTEs or repeaters. See also PDV. LSL Link support layer. Implementation of the ODI (Open Datalink Interface) between the NetWare server LAN drivers and communications protocols such as TCP/IP, allowing network interface cards to service protocol stacks. LSP Link state packet. LT Local termination, or line terminator. The terminating of an ISDN line. LTE Line termination equipment. LTP Link test pulse. a 100 ns pulse transmitted as an idle signal over a 10BASE-T circuit every 16 ms in the absence of data. See also FLP burst. LU Logical unit. In Systems Network Architecture (SNA), one end of a communications session. NA Numerical aperture. Roughly equivalent to the sine of the acceptance angle of an optical fiber, multiplied by its refractive index. NAC Null attachment concentrator. Hub that is not attached to either the primary or secondary ring of an FDDI network. NADN Nearest active downstream neighbor. In token ring networks, the ring station directly downstream from any given ring station. See also NAUN. NAK Negative acknowledgment. A communication that indicates that a message was not received, or that a terminal does not wish to transmit. See also ACK. nanosecond (ns) 1 x 10-9 second = 0.000000001 second (one billionth of a second). NANP North American Numbering Plan. Conforming to ITU E.164, the international standard for numbering plans, this Public Switched Telephone Network plan provides a standard format for telephone/fax numbers in the United States, Canada, Bermuda, and many Caribbean countries. NAS Network Access Server. Equipment located at an ISP, acting as interface between a remote user and an Extranet switch, to provide tunneling or VPN capability.
NAU Network accessible unit or network access unit. A communications controller that attaches to a local network, implements the network protocols, and provides an interface for device attachment. Network addressable unit. A program or set of programs that carries out well-defined functions in a network and represents the source and destination of data in a network. NAUN Nearest active upstream neighbor. In token ring networks, the ring station directly upstream from any given ring station.The NAUN is responsible for beginning the beacon removal process in a beaconing ring. See also NADN. NauticaTM family Bay Networks ISDN routers that provide high-performance remote access to ISDN networks. NBMA Nonbroadcast multi-access. NC Network control. NCETM Network Control Engine. Bay Networks product that gathers, analyzes, and reduces management data collected in its own domain. Forwards only high-level data to the management console to decrease network traffic and reduce required processing power of the Optivity network management station. NCP Network Control Protocol or Network Control Program. Software that manages the traffic between workstations and the host. In a LAN, it is called a network operating system, resides in the server, and manages requests from the workstations. NCS Network Control Signaling. NDIS Network device interface specification or network driver interface specification. A device driver specification developed by Microsoft and 3Com that is independent of the NIC hardware and the network protocol. NEBS Network Equipment-Building System. Criteria, as referenced in Bellcore SR-3580, designed to insure that equipment placed in the telephone network meets certain minimum standards. NETarchitectTM A network configuration management system allowing the user to retrieve, modify, store, and distribute configuration files on network devices from a central management station. See also Optivity Network Management SystemTM (NMS). NetBIOS Network Basic Input/Output System. An interface and upper-level protocol developed by IBM for use with a proprietary adapter for its PC network product. NetBIOS provides a standard interface to the lower networking layers. Essentially, the protocol provides higher-level programs with access to the network.
NETGEARTM An independent division of Bay Networks, providing adapters, hubs, routers, and switches to the small office/home office (SOHO) market. This product family's simple, cost-effective connectivity solutions enable end users to make the most of the latest networking technologies without the need for extensive networking experience or knowledge. NetID Network identification. The network part of an IP address. See also Class A/B/C address. NetWare Novell's local area network operating system based on its proprietary Internetwork Packet Exchange (IPX) and Sequential Packet Exchange (SPX) protocols. network A group of nodes that communicates using a common channel. A group of computers, terminals, and other devices and the hardware and software that enable them to exchange data and share resources over short or long distances. A network can consist of any combination of local area networks (LANs) or wide area networks (WANs). See also LAN, MAN, WAN. network address (1) A protocol-specific address on various media devices that identifies the segment or area where a specific station resides (such as IP, Novell IPX, or DECnet). (2) The network portion of an IP address. Assigned Internet network addresses are globally unique. See also Class A/B/C address, IP address, subnet address. (3) A unique number assigned to each system on a network, consisting of the network number and the system number. Also called Internet address. network bridge A device linking two separate networks that share common network addressing protocols but may differ at higher-level protocols. network center A centralized location where shared resources, network backbones, and user connection concentrations are installed and controlled. In a collapsed backbone architecture, the physical point of central administration where all segments are spliced, terminated, and accessed. In a hierarchical backbone architecture, a network may have multiple network centers. Network FabricTM A managed, high-speed communications system that supports new classes of enterprise and multienterprise applications such as electronic commerce, desktop video conferencing, and medical imaging; easily expands and evolves as an organization grows. Refers to all the communications in layers 1, 2, and 3 of the OSI reference model (intelligent hubs, routers, bridges, and switches) that create the physical network. network layer The OSI layer that is responsible for routing, switching, and subnetwork access across the entire OSI environment. Layer 3 of the OSI model defines protocols that govern data routing. network management (1) Administrative services performed to manage a network. Software programs that gather information about network activity. To facilitate interoperability, network managers have agreed on popular standards for network management software operation, including the Simple Network Management Protocol (SNMP) and RMON.See also agent, NMS. (2) Five functional areas defined by the ISO (International Standards Organization) as necessary to keep a network operating near maximum efficiency. These are: configuration management, fault management, security management, performance management, and accounting management.
network number Network address. A unique identifying number that a network administrator assigns to each separate attached network during installation of each file server or other networked device. NEU Network extension unit. NEXT Near end crosstalk. A transmission characteristic of UTP cable that is measured to ensure permissible distances for transmissions across the cable. NFS Network File System. Sun Microsystems distributed file-sharing system that allows a computer on a network to use files of another computer on another network. NHC Next hop client. NHRP Next hop resolution protocol. NHS Next hop server. NHU Network Hub Unit. A concentrator/repeater for StarLAN networks. NIA Network Interoperability Alliance. An association of information and networking companies addressing network interoperability issues and coordinating multivendor testing. http://www.nia-alliance.com/ NIC Network Information Center. Network interface card. NIC card Network interface controller card. A peripheral board that controls the connection to a LAN in a PC, workstation, server, or other such computer, usually residing in an expansion port. NIF Neighbor information frame. A part of the SMT next station addressing process that determines which FDDI station is upstream and which is downstream when two stations are on the same FDDI ring. NIS Network information services. The security and file-access databases on UNIX systems. NIST National Institute of Standards Technology. The standards-defining agency of the U.S. government, part of the Department of Commerce, formerly called the National Bureau of Standards. NLRI Network layer reachability information.
NLSP NetWare Link-State Protocol. Link-state routing protocol developed by Novell for handling IPX traffic in large internetworks. NMA Network management application. (1) Application that provides the mechanism for the network manager to read and alter data, control the network, and access reports. (2) Bay Networks ATM software that manages the LattisCell family of switches and the EtherCell Ethernet-to-ATM switch. NMC Network management console. Dedicated PC or UNIX workstation that runs network management software and requests information from agents. NMI Network management interface. Part of the backplane bus architecture of a hub that allows communications between installed network management modules and other devices on the LAN. NML Network management layer. The layer in the Telecommunications Management Network standard governing network functions including monitoring, management, and control. NMM Network management module. A slot or module that resides in a hub chassis, collects network management data from the hub, and reports it to the network management application. Also performs interconnection, termination, and retiming functions. Each media access method (Ethernet, token ring, FDDI, ATM) has its own network management module. NMP Network Management Protocol. A seven-layer communications protocol based on the OSI reference model and AT&T-defined application language and formatting conventions. NMS Network management station. A workstation supplied with a network management software application that enables it to communicate with and manage network management agents. See also agent, network management. Network management software. Network management system. See also Optivity Network Management SystemTM (NMS). NMVT Network management vector transport. NNI Network-to-network interface. An interface connecting private or public switches. A private NNI is between two private network switches within a building. A public NNI is between public switching devices that create a WAN. The NNI specification can be applied in both switch-to-switch and network-to-network situations. See also UNI. Network node interface. The interface at a network node that is used to interconnect with another network node. nodal processing delay The overall time it takes to move data from an input port to an output port. Nodal delay is dependent on two factors: speed of the node and network load of the node.
node An addressable device, such as a personal computer, server, switching point, bridge, or gateway, that is connected to a network at a single location. A generic term applied to an active element in a network (for example, FDDI station or concentrator), also commonly called a "host." Node Security An Optivity security feature that allows you to restrict packet delivery only to the port with an authorized address that matches the MAC destination address of the transmitted packet. NOS Network operating system. An extensive program that provides communications between LAN workstations and controls access to the file server. NPSI Network Packet Switching Interface. IBM's Network Control Program (NCP) software allowing SNA hosts to attach to X.25 networks, supporting virtual circuits that appear to SNA hosts as point-to-point (SDLC) links. NRM Normal response mode. HDLC mode used on links with one primary and one or more secondaries, allowing a secondary to transmit only after being addressed by a primary. It can then send a series of responses. NRZ Nonreturn to zero. Signaling method that does not automatically return to a neutral state after each bit transmission. NRZ-I Nonreturn to zero - inverted. See NRZ. NRZL Nonreturn to zero level. See NRZ. ns Nanosecond(s). 1 x 10-9 second = 0.000000001 second (one billionth of a second). NSAP Network service access point. The point at which the OSI Network Service is made available to a transport entity. NT1 Network Termination 1, also Terminator or Terminal. The point where the ISDN network (phone company) connects to user equipment. NT2 Network Termination 2, also Terminator or Terminal. The point where switching services connect to user equipment. NTU Network Terminating Unit. Device serving as interface between customer premise equipment and the carrier facility, regenerating and conditioning digital signals in both directions.
NUI Network user identification. A unique alphanumeric set of characters provided to dial-up users to identify them to packet switched networks around the world. NVE Network visible entry. NVFS Nonvolatile file system. NVRAM Nonvolatile random access memory. Program memory designed to hold information during loss of power. NVTS Network virtual terminal service. OA Outgoing access. OAM&P Operations, Administration, Maintenance, and Provisioning. Network management function that is used on a T-Carrier and SONET networks. OC-1 Optical Carrier-level 1. An optical fiber transmission system, with speed of 52 Mb/s. OC-3 Optical Carrier-level 3. An optical fiber transmission system that carries 3 STS-1 signal levels at 155 Mb/s. OC-3c Optical Carrier-level 3 concatenation. An optical fiber transmission system that carries STS-3c frame structures at 155 Mb/s. The "c" stands for unchannelized frame structure, in SONET. Concatenation refers to the linking together of multiple STS-1 frames to form an envelope capable of carrying super rate payloads, such as when SONET carries ATM cells. OC-12 Optical Carrier-level 12. An optical fiber transmission system that carries 12 STS-1 signal levels at 622 Mb/s. OC-12c Optical Carrier-level 12 concatenation. An optical fiber transmission system that carries STS-12c frame structures at 622 Mb/s. The "c" stands for unchannelized frame structure, in SONET. Concatenation refers to the linking together of multiple STS-1 frames to form an envelope capable of carrying super rate payloads, such as when SONET carries ATM cells. OC-48 Optical Carrier-level 48. An optical fiber transmission system that carries 48 STS-1 signal levels at 2.488 Gb/s. octet Eight bits. A precise standard term for an 8-bit byte, often used in networking instead of byte, because some systems have bytes that are not 8 bits long. OCU Office Channel Unit. The central office equivalent to a channel service unit (CSU) device.
ODI Open Datalink Interface. Novell's extension to its Open Datalink Interface specification. ODI isolates the protocol stack from the network adapter drivers allowing hardware independence for network connectivity. OEM Original Equipment Manufacturer. OID Object identifier. A (MIB) series of nonnegative integers, separated by periods (dots), that delineates the path to the object through the SNMP global naming tree. OmniViewTM Bay Networks device-monitoring tool allowing the user to track the performance of multiple hubs within a single window. Part of the Optivity network management suite. onboard transceiver A transceiver (equivalent to an IEEE 802.3 MAU) implemented as part of the internal circuitry of an Ethernet network interface card; also called internal transceiver. one-way transmission A switch link that can either receive data from or transmit data to another switch, but not both. on-net routing Routing between multiple IP subnets on the same physical port. OOF Out of frame. OpenBayTM A Bay Networks Corporate Program for partner development of modules compatible with Bay Networks modular chassis. OpenNET A networking system for Intel Corporation. optical cable A thin cable with a glass or plastic core that passes light instead of electrical signals. optical power budget An allowance for attenuation in a fiber optic link, the difference between transmitter power and receiver sensitivity. Optivity® Bay Networks network management application that builds on Novell ManageWise or HP OpenView DOS systems, or on SunNet Manager, HP OpenView, or IBM NetView for AIX UNIX systems. Optivity Call ReporterTM Bay Networks carrier-class network management application generating comprehensive reports from statistical information gathered from Bay Networks Model 8000 and Model 5399 RACs. See also VersalarTM.
Optivity CampusTM Bay Networks network management software that provides end-to-end management for midsize Ethernet and token ring networks on a Windows platform. Supports the full line of Bay Networks networking products. Optivity AnalysisTM Bay Networks suite of RMON and RMON2-based network management tools, including Real Time Monitoring and the TrafficMan application, for viewing and managing enterprise networks. Optivity Analysis can run on top of an existing network management system or as a standalone application. Formerly known as Optivity Design and Analysis. Optivity EnterpriseTM Bay Networks network management suite of tools and applications for UNIX-based management platforms. The suite consists of Optivity NMS, Optivity Planning, Optivity Analysis, and NETarchitect. Optivity NMS InternetworkTM Bay Networks network management applications providing tools to manage router-based internetworks. Optivity NMS LANTM Bay Networks enterprise network management applications for LANs composed of hubs, frame switches, and cell switches. Optivity Network Management SystemTM (NMS) Bay Networks graphical network management application suite running on Sun Solstice Domain Manager, HP OpenView Network Node Manager, and Tivoli TME 10 NetView for AIX platforms. The suite tools and applications consist of Optivity NMS LAN, Optivity NMS Internetwork, and NETarchitect. Optivity PlanningTM Bay Networks suite of enterprise management tools including NetReporter and DesignMan applications. Optivity Planning allows monitoring and managing of an enterprise network as one cohesive system, from the enterprise to the device level. Optivity WorkgroupTM Bay Networks network management software for small hub-based, router-based, and integrated hub/router internetworks. Includes EZ LAN and EZ Internetwork applications. See also EZ InternetworkTM, EZ LANTM. OS Operating system. A master control program that manages the internal functions and resources of a computer and provides access to memory, applications, storage, and peripheral devices. See also NOS. OS/2 Operating System 2. An IBM registered trademark product. OSI Open Systems Interconnection. International standard computer network architecture designed by ISO committees. An international standardization program to facilitate communications among computers from different manufacturers. See also ISO. OSI reference model Open Systems Interconnection reference model. A seven-layer (physical, data link, network, transport, session, presentation, and application) network architecture standardized within the International Organization for Standardization (ISO) (refer to ISO 7498-0). The OSI reference model is the basis for defining network protocol standards, so any OSI-compatible device can communicate with any other OSI-compatible device for a meaningful exchange of information. In the OSI model, each layer provides a
subset of LAN services and requires only services from the layer below it, resulting in a logical structure for network operations. See also ISO. OSPF Open Shortest Path First. A link-state protocol in the IP suite that enables routers to exchange information regarding topological changes within the network, as the link state database is modified. With this information, each router builds a shortest-path tree with itself as the tree root to identify the shortest path from itself to each destination and to build its routing table. OUI Organizational Unique Identifier. A company-specific portion of a MAC address. out-of-band A remote connection using a communication channel outside of the network (in-band) facilities. This connection typically requires a connection through a local network, using modems at the local and remote devices, and it is useful when network communications are not available. out-of-band-management A communication server application that uses the serial port on any network device, such as a router, to diagnose and manage devices when network communications are not available. out-of-band signaling A method of signaling that uses a frequency outside of a carrier channel or protocol normally used for information transmission; for example, signaling between a network management station and a network management module occurs over a telephone line rather than over the network. oversized packet An Ethernet packet greater than 1518 bytes, including the address length and cyclic redundancy check (CRC) fields. May be caused by jabbering or defective devices in the network. Can cause FIFO buffer overflow, collisions, fragments, CRC errors, or alignment errors. In the case of 802.1q tagged packets, the size needs to exceed 1522 bytes. packet A group of bits, including data and control signals, arranged in a specific format and transmitted as a whole. The structure of a packet depends on the protocol. In general, a packet includes three principal elements: control information (such as destination, origin, length of packet), data to be transmitted, and error detection and correction bits. An information block identified by a label at layer 3 of the OSI reference model. packet capture A router-based utility used for capturing packets on a given interface, supporting various router platforms and media types. packet filter The determination of whether to forward or drop a packet according to a prescribed set of criteria, such as source or destination or packet length. Helps to control network traffic. packet switched network A communications network that uses packet switching technology. packet switching A communications paradigm in which packets (messages) are individually routed between hosts, with no previously established communication path. See also circuit switching, connection-oriented, connectionless.
packet transfer mode A transfer mode in which the transmission and switching functions are achieved by packet-oriented techniques, so as to dynamically share network transmission and switching resources between a multiplicity of connections. PAD Packet assembler/disassembler. A software module that receives characters from terminals, assembles them into packets, and sends them. The receiving end disassembles the packets and sends the characters to a terminal. PAP Password Authentication Protocol. A method of establishing security on PPP links where the caller must provide a password in order to establish the link. parallel LAN backbone A form of collapsed backbone in which multiple segments are distributed to each wiring closet, providing access to all segments from each wiring closet. partition (1) Electronic isolation of an Ethernet device from network communications. Bay Networks products support automatic partitioning of ports on fault or error conditions. (2) A reserved or isolated segment of memory or disk storage on a computer or network device. passive hub Central connecting device in a network that joins wires from several stations but does not provide signal processing or regeneration. See also active hub, intelligent hub. PassThruTM ports PassThru ports provide a direct connection from the StackProbe port to the monitored server or switch, without using hub capacity. See also StackProbeTM. patch cable Length of wire or optical fiber cable used to connect the concentrator ports to locations on a patch panel. The type of patch cable to use is determined by (1) the cable type (single-mode fiber, multimode fiber, STP, or UTP) and (2) the type of patch panel and wall outlet to which the cable is connected. patch panel An array of jacks through which a number of circuits can be connected or interconnected by patch cables. payload The data portion of an ATM cell or packet. The cell consists of a 5-octet header and a 48-octet payload. payload type (PT) Part (3 bits) of an ATM cell header that indicates the type of information that the cell is carrying; for example, user data or management information. PBX Private branch exchange. A private telephone exchange, such as a company switchboard, typically used and operated by a business, that provides internal communication and access to the public network. Most PBX systems are automated to allow users to dial a specified digit to obtain an outside line. PC-MAC-LCT PC MAC Link Confidence Test.
PCI Peripheral component interconnect (bus). A local bus designed by Intel Corporation that provides a high-speed data path between the CPU and up to 10 peripherals. Can coexist within a computer with the ISA or EISA bus. PCM Physical Connection Management. Part of the station management specification of an FDDI network. Resides in the physical sublayer and is responsible for the initialization of connections and signaling between ports. Pulse code modulation. The most common method of encoding an analog voice signal into a digital bit stream. PCMCIA Personal Computer Memory Card International Association. PCS Physical Coding Sublayer. A part of the physical layer of the OSI model (layer 1). See also OSI reference model, PMA, PMD. PDH Plesiochronous Digital Hierarchy. The multiplexing hierarchy used in T-Carrier and E-Carrier voice communication networks. Plesiochronous means "almost synchronous," referring to the process of adding extra bits to multiple 2 Mb/s channels to achieve the same bit rate. See also SDH. PDN Public Data Network (X.25). A packet switched wide area network under government control. Packet data networking technology, level 3 of X.25, defines how user messages are broken into packets, how calls are established and cleared, and how data flows across the entire PDN. PDNs Packet data networks. PDU Protocol data unit. The unit of data in the OSI reference model containing both protocol-control information and user data from the layer above. The block of information is exchanged between two processes within communicating machines. PDV Path delay value. The time it takes an Ethernet packet to travel the longest path across the network. PEP Packet Exchange Protocol. A Xerox protocol used internally by Novell NetWare to transport internal NCP (NetWare Core Protocol) commands. performance management One of the five network management application areas defined by ISO; concerned with evaluating the behavior and effectiveness of network communications. See also network management, ISO. per-port ring selection The ability to associate a workstation connected to a specific port with any token ring supported within a hub. Also known as per-port switching and configuration switching. per-port segment selection The ability to associate a workstation connected to a specific port with any Ethernet segment supported within a hub. Also known as per-port switching and configuration switching.
phantom circuit A circuit derived from two pairs of wires called side circuits, arranged so that each pair of wires is a circuit in itself while also acting as one conductor of the phantom. Used in token ring networks to insert and deinsert a station in the ring based on station power. PHY Physical layer. The sublayer of the various physical layer protocols that provides the clock speed, data-encoding scheme, and control symbols used in the network. physical layer Layer 1 of the OSI reference model. Provides the means to activate and use physical connections for bit transmission. Defines protocols governing transmission media and electrical or optical signals. In plain terms, the physical layer provides the procedures for transferring data across a network physical medium. physical media Any means in the physical world for transferring signals between OSI systems. Considered to be outside the OSI reference model and, therefore, sometimes referred to as layer 0. The physical connector to the medium can be considered as the bottom interface of the physical layer (layer 1 of the OSI reference model). physical unit (PU) A component of an SNA (Systems Network Architecture) node that controls the resources of the node and reports errors. The access method in the node. PI Primary in. In an FDDI network, one of the ports associated with a dual attached device. PING Packet Internet Groper. A program useful for testing and debugging networks. PING sends an echo packet to the specified host, waits for a response, and reports success or failure and statistics about its operation. PLD Programmable Logic Device. PLP Packet Level Protocol. A protocol that defines the means of packet transfer between an X.25 DTE and an X.25 DCE. It supports packet sequencing, flow control, and error detection and recovery. plug A termination on the end of a cable, designed to provide contact with a socket, receptacle, or jack. PMA Physical Medium Attachment (sublayer). A part of the physical layer of the OSI model (layer 1). See also OSI reference model, PCS, PMD. PMD Physical medium dependent or physical layer media dependent (sublayer). A part of the physical layer of the OSI model (layer 1). See also OSI reference model, PCS, PMA. PMF Parameter management frames. A type of station management frame in FDDI used by a station to read or write SMT MIB objects, allowing remote management of the station.
PNNI Private network-to-network interface. A hierarchical, dynamic link-state routing protocol for building large-scale ATM-based networks. PNNI defines signaling requests to establish point-to-point and point-to-multipoint connections across those networks. PO Primary out. In an FDDI network, one of the ports associated with a dual attached device. Generally connects to a trunk ring. PocketProbeTM A Bay Networks Series 1000 Ethernet web-based network monitoring device providing instant network management via RMON/RMON2 instrumentation. The probe is compatible with Optivity Network Management System applications. See also Optivity Network Management SystemTM (NMS), RMON, RMON2. POH Path over head. Part of the SONET framing structure that provides the SPE with overhead information. See also SPE. polling An inquiry from the CPU, central hub, or controller asking for a specific set of data (for example, statistics) from a device, device subsystem, or application (such as a specific protocol or interface). polling interval The time (in seconds) between data requests or inquiries initiated by a CPU and received by a subordinate device or device subsystem. POP Point of presence. The (local or long distance) carrier's switching central office. For an Internet service provider (ISP), a POP is a local number that a user can call to connect to the ISP. port A place where data can enter or leave a network device or computer. On a PC, the serial and parallel ports are external sockets for plugging in communications lines, modems, and printers. POTS Plain Old Telephone System or Plain Old Telephone Service switching circuit. The analog phone lines capable of making and receiving calls. power budget An allowance for attenuation in a fiber optic or broadband link, the difference between transmitter power and receiver sensitivity. power supply A component in a device that coverts external AC power to DC power for the device internal circuitry. PPP Point-to-Point Protocol. Protocol between the terminal and the router. A communications protocol that provides dial-up access to the Internet. PPP encapsulates common network-layer protocols in specialized Network Control Protocol packets; for example, IP over PPP (IPCP) and IPX over PPP (IPXCP). PPTP Point-to-Point Tunneling Protocol. A tunneling protocol using existing Internet protocols of PPP and TCP/IP to create Virtual Private Networks (VPNs). See also tunneling, VPN.
PPX® Parallel Packet Express. The 1 Gb/s processor interconnect in Bay Networks BLN and BCN routers that distributes data to one of four 256 Mb/s data paths to maximize performance and ensure continuous operation. premises cabling Building wiring that runs from network stations to wiring closets or between wiring closets; includes the horizontal cabling on each floor and the backbone or vertical cabling between floors. Also called distribution cabling. premises concentrator A modular Bay Networks concentrator, such as a System 3000 concentrator, suitable for larger networks. presentation layer Layer 6 of the OSI reference model, which determines how application information is represented (that is, encoded) while in transit between two end systems. See also OSI reference model. PRI Primary rate interface or primary rate ISDN (Integrated Services Digital Network). In North America, PRI consists of 23 B channels and 1 D channel for a combined capacity of 1.544 Mb/s. In Europe, 30 B channels and 1 D channel provide a combined capacity of 2.048 Mb/s. See also BRI, ISDN. primary in (PI) In an FDDI network, one of the ports associated with a dual attached device. primary NMM A Bay Networks network management module configured to provide retiming and intended to be active and functional.The main (online) network management module is in charge of gathering concentrator statistics and status and reporting them back to the control console adapter in the network management control console. primary out (PO) In an FDDI network, one of the ports associated with a dual attached device. Generally connects to a trunk ring. primary ring One of the two logical token paths in a dual ring. It is the primary data path. See also secondary ring. prioritization Process performed by filters to assign preference to time-sensitive or mission-critical traffic, thereby reducing the occurrence of session timeouts and improving application response time. Priorities can be assigned based on protocol, source or destination network, packet type, or protocol-specific or other identifiable fields. PRMD Private management domain. A private domain to which message transfer agents (MTAs) send mail. Usually a corporate or government agency e-mail system connected to an administrative management domain (ADMD). probe Device attached to a network that allows you to get information on the network to the packet level. PROM Programmable read-only memory. Read-only memory (ROM) factory-programmed for use in a specific computer.
promiscuous monitoring The process by which a device, such as an NMM, monitors network performance by examining every packet transmitted on the network. protocol A formal set of rules developed by international standards bodies, LAN equipment vendors, or groups governing the format, control, and timing of network communications. A set of conventions dealing with transmissions between two systems. Typically defines how to implement a group of services in one or two layers of the OSI reference model. Protocols can describe low-level details of machine-to-machine interfaces or high-level exchanges between allocation programs. protocol control information Information exchanged between corresponding devices, using a lower-layer connection, to coordinate data transfer (sending and receipt) between one another. See also cell header. protocol prioritization An outbound filter mechanism that lets you specify priority queues of the router to use when transmitting packets. Supports WAN protocols only. See also traffic filter. PRT Pulse repetition time. PSE Path switching elements. An integrated circuit that provides sophisticated management functionality to FDDI products. PSN Packet-switch node. The name of an ARPANET packet switch. PSTN Public-switched telephone network. The worldwide voice telephone network; the local telephone company. PT Payload type. Part (3 bits) of an ATM cell header that indicates the type of information that the cell is carrying; for example, user data or management information. PTT Post Telephone and Telegraph. International administrations that regulate and perform telecommunications services, per ITU-T standards. See also CEPT. PU Physical unit or peripheral physical unit. A component of a Systems Network Architecture (SNA) node that controls the resources of the node and reports errors. The access method in the node. punchdown block A connecting block used in telephone connections, typically consisting of an insulated base covered by four vertical columns of 50 insulation displacement or wire-wrap connectors; also called splice block, telco block, Type 66 block, or wiring block. PVC Permanent virtual circuit. Dedicated connection between devices manually set up to be used for a single purpose (comparable to having a "leased line"). See also SVC. PVV Path variability value. The amount or value of the shrinkage in the path delay value. The maximum PVV that an Ethernet network can tolerate is 49 bits.
Q.2931 An ITU-T specification defining user-to-network interface signaling for Broadband ISDN. See also ISDN, ITU-T. Q.922A An ITU-T recommendation for data link layer specification for frame mode bearer services. See also ITU-T. Q.922A Frame A variable-length unit of data, formatted in standard frame relay format, transmitted as pure data. QENET Quad Ethernet (link module). QLLC Qualified Logical Link Control. A protocol that transfers IBM SNA data over an X.25 network, part of the Bay Networks X.25 services. QMCT1 Quad multichannel T1. QRSS Quasi-random signal sequence. QSYNC Quad Synchronous (link module). Quality of Service (QoS) A measurement of the service provided to a user. In ATM networks, QoS measurements related to traffic can be divided into two categories: cell level and connection level. In ST2 (Internet Stream) Protocol, the QoS must satisfy data rate and delay characteristics of specific packet streams. QUICC Quad Integrated Communication Controller. Quick2Config® Part of the Bay Networks EZ Internetwork network management application. Simplifies router configuration for Ethernet, token ring, and FDDI networks. R interface Reference interface; also reference point. A physical or conceptual point where two ISDN functions merge. ISDN networks include four main reference interfaces/points: R reference interface. The point between the non-ISDN device and a terminal adapter; the boundary between user equipment and the ISDN network. S reference interface. The point between the terminal equipment and the switching device at the user premises. T reference interface. The point between the user switching device and the subscriber side of the local loop; that is, the wire between the user's phone and the phone company's central office. U reference interface. The point between the NTI and the phone company's central office, where the subscriber side and the network side of the local loop meet. RACTM Remote Access Concentrator. Bay Networks Versalar products, the Model 8000 system and Model 5399 module are dial-in remote access servers. Both support up to 48 T1 modems or 62 E1 modems and have x2
or K56flex capability, featuring industry-leading dial access density, call management, and BayDSP modem technology. See also BayDSPTM, VersalarTM. RADIUS Remote Access Dial-In User Services. A combination of IETF RFCs 2138 and 2139 that provides authentication, authorization, and accounting for remote dial access users. RADSL Rate Adaptive ADSL. A version of ADSL where modems test the (telephone) line and adapt their operating speed to the fastest line speed possible. RAF Resource allocation frame. A type of SMT frame in FDDI that defines the allocation of network resources. RAI Remote alarm indication, or indicator. A signal of an error condition, sent from one end of a SONET path to another, thus providing end-to-end failure indication. RAM Random access memory. The main working memory of a computer in which program instructions and data are stored where they are directly accessible to the central processing unit (CPU). Often called read/write memory to distinguish from read-only memory. range pinging A testing and debugging process that involves sending an Internet Control Message Protocol (ICMP) echo request to a range of IP addresses to determine which devices respond. A response indicates that the device address is active, but it does not specify the device type. RARP Reverse Address Resolution Protocol. Internet protocol used by a diskless machine at startup to find its Internet address. The machine broadcasts a request containing its physical hardware address, and a server responds by sending the machine its Internet address. RAS Remote access server. A server residing at an ISP network to provide tunneling capability from a remote user to the corporate network. See also L2TP, LAC, LNS, TMS, VPN. RBOCs Regional Bell Operating Companies. United States telecommunications companies providing large, traditional networks and services. RD Receive data. An RS-232-C standard hardware signal to carry data from one device to another. Also abbreviated Rx or Rxd. RDBMS Relational database management system. RDF Resource denied frame. A type of SMT frame in FDDI used by a station to respond to an unsupported optional frame class or unsupported version of SMT. RDP
Reliable Datagram Protocol. A protocol that provides reliable datagram service on top of the standard unreliable datagram service provided by the Internet Protocol. real time Pertaining to actual time during which a process transpires. An application in which response to input is fast enough to affect subsequent input, as when conducting the dialog that takes place at terminals in interactive systems. receiver sensitivity The minimum received peak optical power that will produce a recovered electrical signal with minimal timing distortion. redundancy A provision of duplicate, backup equipment and/or software processes in case of primary equipment or system failure. REM Ring error monitor. A ring-resident function that maintains statistical records on token ring operating errors. remote (device) Any network device that is accessible only by means of communication over a digital or analog (dial) network. Remote AnnexTM Bay Networks product family of terminal and communication servers that provides local and remote multiuser system access. Remote Console An Annex communication server application that permits users to manage multiple systems or network devices from a single remote console. See also AnnexTM. remote control access A type of remote access to a network wherein a remote PC dials into and takes control of a PC on the network; only screen and keyboard updates are passed over the connection. remote fault signal An indication of far-end receive failure, as seen by a port that is not receiving a light signal. remote node access A type of remote access to a network where a remote PC or workstation dials into and participates as a fully functioning end node on the network while also taking advantage of the processing power of the remote device (such as a server). remote office An office that is geographically distant from the corporate network. remote signaling A verification of proper connectivity between transmit and receive fibers. Bay Networks 10BASE-FL products include a proprietary version because 10BASE-FL standards do not address remote signaling. repeater A device inserted at intervals along a network to boost and amplify analog signals or regenerate digital signals being transmitted, used to connect segments of a network medium together into a single collision
domain. A repeater helps signals travel farther over a cable because the quality and the strength of a signal decay over distance. A repeater operates at the Open Systems Interconnection (OSI) physical layer. reset packet A packet used to reset a virtual circuit at the interface between the data terminal equipment and the data circuit-terminating equipment. resource Hardware or software that can be shared over a LAN; for example, printers, modems, disk drives, and directories. retiming module A module that implements IEEE 802.3 repeater functions for data entering a concentrator and also provides termination for the concentrator backplane. RF Radio Frequency. Electromagnetic wave frequency used for radio transmissions. RFC Request for Comments. A document (for example, RFC 1483, RFC 1577) describing proposals and standards for internetworking protocols, such as the Internet Protocol (IP). RFI Radio frequency interference. Electromagnetic radiation produced by some electronic or electromechanical devices that can interfere with other radio frequency signals. RI Ring in. The input port of a ring in/ring out concentrator module in a token ring network. RIF Routing information field. A bit field that contains routing information. RII Routing information indicator. The first bit of the source address of a token ring source routed frame; part of the RIF. ring A set of stations wherein information is passed sequentially between stations, each station in turn examining or copying the information, returning it finally to the originating station. ring network A cable network topology characterized by a cable that forms a completely closed loop. Contrast with star and bus topologies. A network in which every node has exactly two branches connected to it. ring topology A network topology where stations are connected to the network at a repeater device. The repeaters are linked to each other to form a single, closed, unidirectional loop. See also topology. RingViewTM Bay Networks System 2000 and System 3000 token ring hub agent feature that provides ring/station-level isolation and nonisolation soft error diagnosis, and gathers and reports station adapter card profiles.
RINT Receive interrupt. RIP Routing Information Protocol. A distance vector protocol in the IP suite (used by IP and IPX network-layer protocols) that enables routers in the same autonomous system to exchange routing information by means of periodic updates. For RIP, the "best" path to a destination is the path with the fewest hops. RIP computes distance as a metric, usually the number of hops from the origin network to the target network. Remote Imaging Protocol. A graphics format designed for transmitting graphics over low-speed lines. RI/RO Ring in/ring out. Connections used to connect token ring hubs together. RIPSO Revised IP Security Option. RISC Reduced Instruction Set Computer. A relatively inexpensive processor that recognizes a limited number of assembly language instructions. RJ-11 A four-contact or six-contact modular connector commonly used in telephones, fax devices, modems, and other analog (dial) network devices. RJ-45 Common term for the type of connector used in terminating 10BASE-T UTP or STP cabling at the NIC or hub. An 8-pin modular connector used for data communications (IEC 603-7). RLC Redundant Line Cord. A BCN configuration supporting two 220 VAC power feeds for system redundancy. See also BCN®. RMON Remote monitoring. An SNMP protocol used to manage networks remotely. It collects statistics from the data link layer of the OSI reference model (layer 2) and enables a management station to monitor network devices from a central location. It provides multivendor interoperability between monitoring devices and management stations (RFC 1757). RMON2 Advanced RMON standard that adds broader vendor compliance and enterprise-wide traffic monitoring at the network through application layers of the OSI reference model, and additional information about network traffic at these layers. See also MIB, SNMP. RMON probe The interface defined by the DCE/MCE assigned to a network segment for RMON data collection. RMT Ring management. RO Ring out. The output port of a ring in/ring out concentrator module in a token ring network.
roaming Moving an end user device from one location to another within a network while still maintaining unique identification and other properties. Mobile devices (for example, phones, computers) in a cellular packet-switched network can roam areas without losing communication. ROM Read-only memory. An integrated circuit for memory storage that permanently stores information, even after power has been switched off. root concentrator The highest-level concentrator in an inverted, tree-structured network. route The path that network traffic takes from its source to its destination. Also, a possible path from a given host to another host or destination. router (1) A device that forwards traffic between networks, based on network layer information and routing tables. It decides which path network traffic will follow, using routing protocols to gain information about the network and algorithms to choose the best route based on a "routing matrix." In OSI terminology, a router is a network layer intermediate system. See also bridge. (2) A protocol-specific internetworking component configured to know which LAN segments it can communicate with and that takes responsibility for getting packets from one segment to another via the best way. A router must be able to recognize all of the different network layer protocols that may be used on the networks they link together. A multiprotocol router can route many different protocols. RouterManTM Bay Networks graphical information display. RouterMan gathers and displays fault and performance statistics for the overall router, individual protocols, and router interfaces. A real-time monitoring, management, and diagnostic application for network routers. router microsegmentation The act of connecting single end users to a dedicated router port (dedicated routed LAN). router module A module that connects physically separated networks, including networks that operate under different protocols or run on different media or are supplied by different vendors. routing The process of efficiently moving data packets among subnetworks by selecting the correct interface and next hop for a packet being forwarded. See also hop, router. routing domain A set of routers exchanging routing information within an administrative domain. See also AD, router. routing protocol Protocol used by routers to report their status to other routers in the network and to keep their internal tables up to date. routing switch A class of switch that integrates IP routing into hardware, allowing IP traffic to move 10x faster than a router (that is, at Gigabit Ethernet speeds). See also AccelarTM.
routing table A table with entries for every route known to the local device. Entries contain data such as the destination address, next-hop address, and various route metrics. RPOA Recognized private operating agencies. R/RH Response/request header. RPSU Redundant power supply unit. In a Bay Networks chassis, a secondary power supply that provides an immediate backup in case the main power supply fails to prevent any impact on the network. RS-232-C The Electronic Industries Association (EIA) standard for the 25-pin (or 9-pin subset) serial interface used to connect personal computers or terminals to communications equipment, such as modems and fax devices. RS-449 The Electronic Industries Association (EIA) 37-pin standard for higher-speed (up to 2 Mb/s) serial binary data interchange using synchronous data-link lines. RSVP Resource Reservation Protocol. Protocol that provides a method for real-time applications to communicate requirements to network elements along the data path. RSVP conveys Quality of Service (QoS) information between network elements and the application. In addition to the data used to directly invoke QoS control services, RSVP carries authentication and policy information needed to manage the use of these services. RTM Release to Manufacturing. RTMP Routing Table Management Protocol. The protocol that lets an AppleTalk bridge or gateway dynamically discover routes to the various AppleTalk networks within an internetwork. RTP Rapid Transport Protocol. A connection-oriented, full-duplex protocol that supports data in high-speed networks at APPN network node end points. RTP supports nondisruptive path switching, end-to-end error recovery, and end-to-end flow and congestion control. RTS Request to send. RS-232-C standard hardware signal requesting permission to transmit. runt packet An Ethernet packet with a frame size between 8 and 63 bytes with frame check sequence (FCS) or alignment errors. The runt packet is presumed to be a fragment resulting from a collision. Rx or Rxd Receive data. RS-232-C standard hardware signal to carry data from one device to another. Also called RD. RZ Return to zero. The signal pauses at zero voltage between each pulse when making zero crossings. S-frame Supervisory frame.
SA Source address. An address in a network frame that designates the source of the packet it is carrying. SABM Set Asynchronous Balanced Mode. SABME Set asynchronous balanced mode extended. A logical link control (LLC) command protocol data unit (PDU) used to establish a link. The SABME command PDU establishes an LLC2 (numbered and acknowledged) connection to the destination LLC that operates in asynchronous balanced mode. SAC Single-attached concentrator. A hub that offers a single attachment to the FDDI network, usually to the primary ring. SAP Service access point. The point at which the services of a protocol layer are made available to the next higher layer. Each service access point has a SAP address, by which the particular entity that is employing a layer service can be differentiated from all other entities that might also be able to use that layer service. Service Advertising Protocol (in IPX). A Novell protocol that provides a means for servers to advertise their services to routers and other servers. SAR Segmentation and reassembly. In ATM, a sublayer of AAL; a process performed on ATM information cells. SAS Single-attached (concentrator) station. A station that has a single attachment to the FDDI network, usually to the primary ring. save and restore The ability of many Bay Networks products to save and restore network management and host module configurations after a power cycle or the hot-swap of a unit. SBI Stop bracket initiation. SC Session control. SC connector Square/subscriber connector. A square-ended connector for fiber optic cable. See also ST connector. scalability The ability to grow and adjust network hardware and software resources according to user demand for communication services. SCC Serial communication controller. SCP Session Control Protocol. SCS SNA character string.
SCSI Small Computer System Interface. ANSI-defined high-speed parallel interface that uses one computer port to connect to peripheral devices in a daisy-chained configuration. SD, SDEL Start delimiter. Single byte that marks the beginning of a token ring frame. SDDI Shielded twisted pair (STP) FDDI. Early, proprietary schemes for running 100 Mb/s FDDI over twisted pair wiring. SDDI was replaced by the FDDI TP-PMD standard. See also TP-PMD. SDH Synchronous Digital Hierarchy. A standard technology for optical fiber-based synchronous data transmission, running on copper cable. The international equivalent of SONET. See also PDH, SONET. SDLC Synchronous Data Link Control. A protocol based on HDLC (High-level Data Link Control). An IBM term for a link protocol used to transfer data between nodes. SDSL Symmetric Digital Subscriber Line. Data transmission over a single telephone line, in which upstream and downstream transmission rates are the same. SDU Service data unit. Unit of information transferred between a service provider and a service user across the OSI interface. SDV Segment delay value. A value used in calculating the path delay variance in Ethernet networks. secondary NMM A second network management module (jumpered to disable retiming) installed in a hub to serve as a secondary link in case a problem occurs with the primary NMM or the link connected to it. secondary ring One of the two logical rings of an FDDI network. It can be used as a backup to the primary ring and also to provide additional bandwidth for data. See also primary ring. security management One of the five network management application areas defined by ISO; includes tools that allow the network manager to restrict access to various resources in the network. See also network management, ISO. segment (1) An electronic path between two network devices. (2) In structured networking, the physical set of end stations (both users and elements) that form an Ethernet collision domain. The boundaries of a collision domain are defined by bridges or routers. (3) An Ethernet backplane path in a hub, more precisely known as a backplane segment. (4) A port or group of ports defined by their connection together. Ethernet segments can be isolated, local, backplane, or cascaded. Token ring segments can be isolated, local, or backplane. segment (physical) In Ethernet, a single section of bus-type transmission media. In token ring, a single ring of transmission media containing cables, components, and lobes. In FDDI, a single dual ring of transmission media.
segment splicing Technique used in structured networking to accommodate users from a variety of locations who must be in the same network. A network center splices subsegments from different wiring closets to connect them as a full segment. segmentation (1) The process by which a network protocol breaks long frames into multiple, smaller PDUs. (2) The act of breaking segments (rings) into multiple smaller segments (rings); for example, to divide a large network into separate smaller networks for the purpose of increasing performance. segmentation and reassembly (1) In ATM, a sublayer (SAR) of AAL; a process performed on ATM information cells. (2) In APPN, a flow control operation that functions at SNA layer 4. server A computer or specialized device that provides and manages access to shared network resources, such as hard disks and printers. See also client. service bit rate The bit rate that is available to a user for the transfer of user information. service port A 9-pin male serial port on a module used to set configuration information such as the module telephone number, location, key, and retiming status from an attached terminal. session layer Layer 5 of the OSI reference model. Establishes, maintains, and controls a communications session between clients and servers or between peers on a network. SF Superframe format. SFD Start-of-frame delimiter. SFM Switch Fabric Module. The Bay Networks Model 5720 ATM Switch Fabric Module is a 16-port ATM-based switch that supports general, switched high-performance network connections. shared access Shared-media terminology meaning that all devices attached to the LAN share a single communications medium channel, usually a coaxial, twisted pair, or fiber optic cable. shared LAN The original LAN configuration in which stations share a single communication channel using a MAC. All stations receive the transmissions of all other stations. Station operation is half-duplex: there can be only one station originating data on the LAN at one time, determined by the MAC protocol. The aggregate bandwidth of all the stations is limited to that provided by the LAN bit rate. See also switched LAN. SI Secondary in. In an FDDI network, a port that connects dual attached devices, typically to trunk rings. SIF Status information frame. A type of station management frame in FDDI that transmits and receives information about the configuration and operational parameters of other stations.
SIG SMDS Interest Group. signaling virtual channel A virtual channel for transporting signaling information. silver satin A low-performance telephone cable that is flat in shape and typically has a silver vinyl jacket, used for telephone patch cables and horizontal distribution cables but not suitable for high-speed data applications. SIMM Single inline memory module. SIP Switched multimegabit data service (SMDS) Interface Protocol. The protocol used to support SMDS service, consisting of the level 3 protocol data unit containing source and destination addresses and an information field up to 9188 bytes long. See also SMDS. SIS Switched Internetworking Services (BaySIS). SLC Serial link connector. Asynchronous expansion module for the Annex 3 and the Remote Annex 4000. See also AnnexTM, Remote AnnexTM. SLIP Serial Line Internet Protocol (IP). A TCP/IP protocol that allows IP packets to be transmitted over a serial link, such as a dial-up or private telephone line. slot A location in a network device where a module can be inserted. SmartSwapTM Feature in Bay Networks products that allows a host or network management module to be inserted or removed while the chassis remains functional and is receiving power. Also known as hot-swap. SMB Server message block. A message format derived from the Microsoft/3Com file sharing protocol used to transfer file requests (such as open, close, read, write) between clients and servers. It provides services at the application layer (layer 7) of the OSI reference model and is used in networks such as LAN Manager, LAN Server, and Windows NT. SMDS Switched multimegabit data service. A connectionless, high-speed data service offered by most telephone companies that allows LANs to connect across a wide area network. Other common WAN services include frame relay, PPP, and X.25. SMF Single-mode fiber (FDDI networks). A laser-driven optical fiber whose core diameter is small enough to limit transmission to a single bound mode, commonly used in long distance communications in excess of three miles. See also MMF.
SMF-PMD Single mode fiber-physical medium dependent. A standard for the physical medium dependent (PMD) sublayer that sets the specifications for operating FDDI protocols in a single-mode fiber environment and extends the basic FDDI link distance to 60 kilometers. SMIT System Management Interface Tool. SMP Standby monitor present. SMT Station management. An integral specification within the FDDI standard that specifies the network management interface for each protocol layer. SMTP Simple Mail Transfer Protocol. A service designed specifically for electronic mail that functions as a unified post office for addressing mail to all users on all nodes of wide area and local area networks. SN Switch NodeTM. A Bay Networks modular, 5-slot Ethernet frame switch providing wire-speed forwarding of network traffic at OSI layer 3. The Switch Node's layer 3 switching capability combines high-speed layer 2 switching with IP routing capabilities. The Bay Networks Accelar product family provides the latest routing switch technology. See also AccelarTM. Subarea node. SNA Systems Network Architecture. A proprietary network architecture used in IBM systems to connect terminals to a mainframe. SNAP Subnetwork Access Protocol. A version of the IEEE local area network logical link control frame similar to the data link level transmission frame that allows the use of nonstandard higher-level protocols. sniffer A device or software subsystem that functions as a protocol analyzer and statistics probe on a network. SNM Switched net module. SNMP Simple Network Management Protocol. A standard for network management that uses a common software agent to manage local and wide area network equipment from different vendors; part of the Transmission Control Protocol/ Internet Protocol (TCP/IP) suite and defined in RFC 1157. SNMPv2 Simple Network Management Protocol, version 2. A combination of proposal updates to SNMP, most of which deal with security. SNRM Set normal response mode. SO Secondary out. In an FDDI network, a port that connects dual attached devices, typically to trunk rings.
SOH Start of header. A transmission control character used as the first character of the heading of an information message. SOHO Small office/home office. The small office and home-based segment of the computer and networking market. SONET Synchronous Optical Network. A family of fiber optic transmission rates ranging from 51.84 Mb/s to 13.22 Gb/s that provides the flexibility to transport many digital signals with different capacities and to provide a design standard for manufacturers. See also SDH. SPB Session parameter block. SPE Synchronous payload envelope. A SONET frame containing overhead information (POH) and actual user data. See also POH. SpeedViewTM Bay Networks management application for the Centillion 50/100 and Model 5000BH switches. SpeedView LiteTM A Bay Networks graphical configuration and management application used to configure, monitor, and control network traffic on Bay Networks BayStack 301 Ethernet switches. SPEXTM Stack Packet Exchange. Bay Networks high-performance system interconnect (bus extension) that allows up to four individual ASN (Access Stack Node) router/bridges integrated in a stack configuration to act as a single router/bridge entity. SPID Service Profile Identifier. splice block A connecting block used in telephone connections, typically consisting of an insulated base covered by four vertical columns of 50 insulation displacement or wire-wrap connectors; also called punchdown block, telco block, Type 66 block, or wiring block. spliced backbone network A configuration in which users in different physical locations or floors share the same ring and applications, with host connectivity through a separate wiring closet concentrator located physically near each workgroup. In the equipment room concentrator, the connection is made by connecting each of the associated ring segments together by way of a Bay Networks System 5000 token ring backplane. SPP Sequenced Packet Protocol. Xerox Network Systems protocol governing sequenced data. SPS Service Provisioning System. A Bay Networks licensed software program, supporting BayStream Multiservice and Site Manager software.
SPX Sequenced packet exchange. Novell NetWare protocol set implemented over IPX to form a transport layer interface. SQE test Signal quality error test. A collision test signal sent after transmissions by IEEE 802.3 medium attachment units. SQL Structured Query Language. ANSI and ISO standard query language system developed by IBM for use in mainframe applications with relational database systems. squelch A communication function that turns receiver amplifier circuits off when noise is the only signal present. In an Ethernet transceiver, this function prevents noise from propagating to all network segments. SR Source route or source routing. A token ring standard that supports routing frames through a multiple ring. Each source route frame carries information about the route the frame must follow to reach its destination. SRAM Static random access memory or static RAM. A computer memory that retains its contents as long as power is applied and does not need refreshing. SRB Source route bridge or source route bridging. A systems-level concept used in many token ring environments where the end stations take on the responsibility of learning the exact ring-to-ring path a packet must take to reach its destination and provide all that information in a special routing field of the LAN packet. SRF Status report frame. A type of station management frame in FDDI that periodically announces conditions of interest to the FDDI manager, such as configuration changes, undesirable conditions, and MAC neighbor changes. Specifically routed frame. Frame generated by an end station that receives an ARE or STE frame. The SRF contains a list of routing designators and maps a specific path back to the source end station. SRM-F System Resource Module-Front. This optional unit for BLNs and BCNs provides 1 Gb/s total bandwidth and PPX redundancy. SRM-L System Resource Module-Link. Each BLN and BCN includes one SRM-L, which provides a 25-pin D-connector for a terminal or modem to access the Technician Interface (software) for diagnostic and maintenance operations. SRT Source route transparent. A token ring standard that supports both source route and transparent bridging frames between bridges and end stations on multiple-ring token ring networks. SRT bridge Source route transparent bridge. Device that can support both source route and non-source route end stations.
SS Switching System. Associated with SMDS. SS7 Signaling System 7. A standard signaling protocol used in PSTN, supporting advanced calling services. This protocol is supported by Bay Networks Versalar products. See also PSTN, VersalarTM. SSAP Source Service Access Point. An address field used be logical link control (LLC) protocols to identify the specific service access point that initiated a protocol data unit (PDU). SSCP System services control point. SSE Single Sync/Single Ethernet (link module). SSF Silicon Switch Fabric. A part of Accelar routing switches that contains the core switch fabric and the CPU subsystem for chassis operation. The SSF is built into the chassis of Bay Networks Accelar1100/1150 models. An SSF module is available for Bay Networks Accelar 1200/1250 models, including a second optional module for additional redundancy. SSI SMDS to access Server Interface. ST connector Straight-tip connector. An AT&T bayonet connector for fiber optic cable that uses a precision ceramic plug and a flexible sleeve. See also SC connector. S/T interface Subscriber/Transport interface.The boundary between the user and an ISDN network. STA Spanning tree algorithm. An algorithm used to ensure that a single data path between any two stations on an extended LAN is implemented at any specific time. A technique for determining the best path between segments of a multiloop, bridged network. stackable hubs Hubs that look and act like standalone hubs; however, several can be connected together, usually by a short length of cable, to act like a modular hub that can be managed as a single unit. One manageable hub used with a stack can provide the management for all other hubs in the stack. StackProbeTM Bay Networks probe management product incorporating RMON and RMON2 capabilities in a universal, stackable device. See also RMON, RMON2. standalone configuration A network with a single hub. standalone hubs Single products with a number of ports. Usually include some method of linking them to other standalone hubs by connecting with a length of 10BASE5 coaxial twisted pair cable between individual ports on each hub. Usually the least expensive hubs and often not managed. Best suited for small, independent workgroups with fewer than 12 users.
Standard agent A Level 1 SNMP agent for a Bay Networks device. It monitors the device and gathers statistical data in MIB format to report to the network management station. See also agent, Advanced agent, Advanced AnalyzerTM agent. standard Ethernet A coaxial cable specified by the IEEE 802.3 10BASE5 standard, approximately 12 mm in diameter and usually colored yellow, to which devices are attached by means of DB-15 connectors and a cable-mounted transceiver; also called thick coaxial cable or thick Ethernet. StarLAN An obsolete 1 Mb/s 802.3 standard, star-configured Ethernet local area network from AT&T Information Systems, based on 802.3 type 10BASE5 over twisted pair cables. star topology LAN topology in which each peripheral node is connected to a hub by an individual length of twisted pair cable, in a layout resembling a star. Each node is connected to a hub, which acts as a focal point for network cabling. All information passes through the central point and is passed to the nodes. See also bus topology, ring topology. station A device, such as a personal computer, workstation, server, bridge, or router, connected to a network at a single location; also called data terminal equipment, DTE, host, host device, or node. STE Spanning tree explorer. A single frame generated by an end station configured for spanning tree broadcast routing that follows a loop-free path from source to destination. STG SNMP Transport Gateway. Bay Networks software application that provides the integration of SNMP-manageable devices into existing IBM SNA networks. STM Synchronous Transfer Mode. Clocked data transmission, where the receiving device knows when to expect the next unit of data. Synchronous Transport Module. A definition of the electrical level signal rate and frame structure for SDH networks. STM-1 is equivalent to STS-3 for SONET. See also SDH. store-and-forward device A device that receives packets completely on one interface and queues them for transmission out of the destination interface; for example, a device that supports interfaces running at different speeds, such as 10 Mb/s and 100 Mb/s Ethernet. A data-transmission scheme using a message-switching technique that temporarily stores a message at intermediate points before retransmitting it to its next destination. STP Shielded twisted pair (cable). A cable consisting of two insulated wires, twisted together and surrounded by a braided metal shield or foil under the outer insulation. Shielding provides more protection against EMI (electromagnetic interference). See also IBM Cabling System, UTP. Spanning Tree Protocol. Technique based on the IEEE 802.1 standard that detects and eliminates logical loops in a bridged or switched network. When multiple paths exist, the STP algorithm configures the network to use only the most efficient path.
structured cabling A cabling method used to design network cabling structures to universal standards and conformity. With structured wiring, all network stations are physically star-wired to intelligent hubs (hubs that can be monitored easily and turned off if necessary). Structured cabling makes adding users, moving users, or making other physical changes very simple. Supports Ethernet star topology. structured networking A method of designing the network fabric in which workgroup hubs are connected via fiber optic trunks to a hub located at a centralized location, referred to as a network center. Structured networking decouples physical connections from logical associations, allowing networks to be built around the way organizations are structured instead of around the way buildings are structured. STS-3c Synchronous transport signal - level 3 concatenated. Signal obtained by byte interleaving three STS-1 (51.840 Mb/s) signals together. The rate of STS-3c is three times 51.840 Mb/s or 155.52 Mb/s. STS-N Synchronous transport signal level N. A SONET term for a signal obtained by interleaving N STS-1 signals together. STS synchronous payload envelope A 125-microsecond frame structure composed of STS path overhead and bandwidth for payload. The term generically refers to STS-1 SPEs and STS-Nc SPEs. STUN Serial (SDLC) tunneling. Process that allows SDLC traffic to be bridged over token ring LANs. See also SDLC. SUA Stored upstream address. In token ring networks, the stored address of the upstream neighbor. sublayer (1) A division of a layer in the International Organization for Standardization (ISO) Open Systems Interconnection (OSI) reference model; for example, the logical link control (LLC) sublayer in the data link layer (DLL). (2) A division of a protocol layer. subnet A physically or logically independent portion of a network, distinguished by a subnet number. A subnet is to a network what a network is to an internetwork. See also network. subnet address The subnet portion of an IP address. In a subnetted network, the host portion of an IP address is split into a subnet portion and a host portion using an address (subnet) mask. See also Class A/B/C address, IP address, network address. subnet mask A template or filter imposed on an Internet address for the purpose of separating the members of a particular subnetwork. The "1" bits in the subnet mask indicate the significant bit positions in the subnet address; the "0" bits indicate bit positions that are ignored. summing module A Bay Networks module for System 3000 hubs that manages the current between two redundant power supplies.
SuperAgentTM Bay Networks proprietary distributed software that collects and analyzes raw data from embedded device agents within its domain before sending the synthesized data to the management system. SVC Switched virtual circuit. On-demand connection between an ATM or frame relay source and destination that lasts for the duration of the transmission. SVV Segment variability values. The maximum increase to the bit size of the preambles of Ethernet packets as they travel through each repeater on the path. switch A network device that completes or selects a path for data circuits, packets, frames, or cells to follow from a local device input to a specific local output at wire speed or slightly lower. Switches enable simultaneous transmissions to take place, providing up to 155 Mb/s of network bandwidth. switch control module A Bay Networks ATM embedded controller, such as the Model 5740 Switch Control Module, that handles all aspects of chassis operation (switch management, connection management, SNMP control). switch fabric A matrix of binary switching elements across an ATM backplane. Switch NodeTM A Bay Networks modular, 5-slot Ethernet frame switch providing wire-speed forwarding of network traffic at OSI layer 3. The Switch Node's layer 3 switching capability combines high-speed layer 2 switching with IP routing capabilities. The Bay Networks Accelar product family provides the latest routing switch technology. See also AccelarTM. switched LAN A generalized term encompassing all switched approaches to providing LAN information transport, including frame switching, hybrid switching, and cell switching. Also a LAN configuration in which stations connect to a switch, operate in full-duplex mode, and do not use media access control. All stations have access to nearly the total aggregate bandwidth available. switching Establishment of a direct transmission path from a particular station to another station. Switching provides high-throughput (wire-speed) connections on data networks. SwitchManTM Bay Networks software application that manages the Model 3328 Ethernet Switching Engine, monitors switches, monitors LANs, and can be used to simulate alternative LAN designs. SwitchSafeTM An Accelar 1200 feature using two Silicon Switch Fabric modules that provide backup and resumption of switching functionality in case of failure. synchronous Signals that are sourced from the same timing reference. Causes the interval between successive bits, characters, or events to remain constant or "locked in" to a specific clock frequency. SYSCON System Controller. Accounting program in Novell NetWare LANs that enables a file server to charge for network services.
SYS I/O System input/output. System 800TM Bay Networks family of Ethernet hubs for small, standalone workgroups. System 2000TM Bay Networks family of hub products designed for small to midsize networks. Includes Ethernet, token ring, and FDDI hubs. System 3000TM Bay Networks family of hub modules designed for integrated Ethernet, token ring, and FDDI connectivity; internetworking; and network management capabilities. System 5000TM Bay Networks family of multi-LAN switching hubs with host, management, network, and internetworking modules. Allows integration of Ethernet, token ring, FDDI, and ATM network access methods into a single chassis. T.120 An ITU-T standard addressing Real Time Data Conferencing (Audiographics). See also ITU-T. T1 A North American Telecommunications term for a digital carrier facility used to transmit a DS1 formatted digital signal at 1.544 Mb/s. T3 A term for a digital carrier facility used to transmit a DS3 formatted digital signal at 44.736 Mb/s. T-Carrier A family of digital trunking methods supported in North America. The European counterpart is E-Carrier. See also E-Carrier. TA Terminal adapter. A device providing ISDN connectivity to non-ISDN equipment. TB Transparent bridging. A system-level concept where the bridges perform MAC address learning and look-ups to determine whether or not a packet on a LAN must be forwarded to another segment. The bridging function is transparent to the end station because the end station does not need to know if the device it is addressing is on the same physical segment. All Ethernet bridges are transparent. T connector A T-shaped BNC connector used on Ethernet 10BASE2 thin coaxial cable. TC Transmission control. TCL Tool Command Language. A set of scripting commands on the Switch Node platform, supported by the BCC. TCP Transmission Control Protocol. The major transport protocol in the Internet suite of protocols providing reliable, connection-oriented, full-duplex streams. TCP is both an OSI transport layer 4 protocol that
regulates source-to-destination communication over virtual circuits and the portion of the TCP/IP protocol suite that governs the exchange of sequential data. See also IP. TCP/IP Transmission Control Protocol/Internet Protocol. A set of networking protocols designed to link computers from multiple vendors. TCP/IP was originally developed by the Advanced Research Project Agency (ARPA) as part of the UNIX operating system and has been adopted as a networking standard in many government, academic, and technical computing environments. TD Transmit data. RS-232-C standard hardware signal to send data from one device to another; also called Tx or Txd. TDM Time division multiplexer. A device that performs circuit switching. It converts analog signals to digital signals and integrates video, voice, and data applications. TE Terminal equipment. TE1 Terminal equipment 1. ISDN-compatible devices, such as a router with an ISDN/BRI module. TE2 Terminal equipment 2. Non ISDN-compatible devices, such as analog phones and PCs. Technician Interface Bay Networks software providing management access to Bay Networks routers. It may be used to install a router, to maintain router operation, and to monitor and configure various router functions. TEI Terminal endpoint identifier. telco Any telephone company. telco block A connecting block used in telephone connections, typically consisting of an insulated base covered by four vertical columns of 50 insulation displacement or wire-wrap connectors; also called punchdown block, splice block, Type 66 block, or wiring block. telco connector A 50-pin D connector for 25-pair unshielded twisted pair cable. telecommunica-tions closet A central building or room where distribution cabling is switched and terminated and voice and data communications equipment are located; also called communications closet, equipment room, or wiring closet. TELENET A public packet switched network using the CCITT X.25 protocols. It should not be confused with Telnet. Telnet
The Internet standard protocol for remote terminal connection service. The TCP/IP protocol governing the exchange of character-oriented terminal data and described in RFC 854. It allows users of one host to log in to a remote host and interact as normal terminal users of that host. terminal A device that consists of either a video display and keyboard or a teletypewriter that you use to type and view information. A terminal may be connected to either of the RS-232-compatible serial interface ports on the back panel of the desktop terminal unit. terminal emulation A type of remote access to a network where a PC or workstation connects to a host computer by emulating an asynchronous or block mode terminal; for example, a VT100 or VT52 terminal emulator program. terminal emulator A program that allows a computer to emulate a terminal for communication with a mainframe or minicomputer. The workstation thus appears as a terminal, typically a VT100 or VT52, to the remote host. terminal server A device connecting many terminals to a network usually used to reduce the number of cables needed to connect terminals to a mainframe. The terminal server allows terminals to use the LAN as a connection point instead of direct RS-232 serial cables. A terminal server can also connect many network users to its asynchronous ports for dial-out capabilities and printer access. See also LAN. terminator An electrical impedance attached to the open end of a transmission line to eliminate reflections. TFTP Trivial File Transfer Protocol. A simplified version of FTP that transfers files but does not provide password protection, provide directory capability, or allow transmission of multiple files with one command. TG Transmission group. TH Transmission header. thick coaxial cable A coaxial cable specified by the IEEE 802.3 10BASE5 standard, approximately 12 mm in diameter and usually colored yellow; also called standard Ethernet, thick Ethernet, ThickNet, or just yellow cable. thin coaxial cable A coaxial cable specified by the IEEE 802.3 10BASE2 standard, approximately 5 mm in diameter and usually colored black, to which devices attach by means of BNC T-connectors; also called thin Ethernet or ThinNet. threshold A limit value associated with a specific parameter or attribute of device or network performance. Detection of this value triggers an appropriate response from the local or remote systems or device. For example, when a threshold value is crossed, a warning message can be sent or a module or port can be partitioned. throughput The amount of data transmitted end-to-end successfully, per limit of time (usually in a one-second interval).
THT Token holding timer. A counter on an FDDI ring that controls how long a station can transmit asynchronous frames. TIA Telecommunications Industry Association. A national trade organization, including members from communications and information technology companies contributing to voluntary industry standards that promote trade and commerce in telecommunications products. http://www.tiaonline.org/ TIC Token ring interface card or token ring interface coupler. An IBM adapter card that allows a controller to attach directly to a token ring LAN. TIFF Tagged Image File Format. TINT Transmitter interrupt. TIP Terminal Interface Program. TLAP Token-Ring Link Access Protocol. TLI Transport layer interface or transport level interface. An interface for transport services (layer 4 of the OSI reference model) that provides a common language to a transport protocol and allows client/server applications to be used in different networking environments. TMS Tunnel Management Server/System. The Tunnel Management System database resides on a Bay Networks Tunnel Management Server. The database verifies user or domain name information supplied by a remote access server and supplies the server with remote users' tunnel addressing information. See also L2TP, LAC, LNS, VPN. TN3270 Delivery of a 3270 data stream via Telnet, provided as part of the TCP/IP protocol suite. TNC connector Threaded Neill-Concelman connector. A threaded connector for thin wire Ethernet coaxial cable. See also BNC connector. token A sequence of data bits passed from one node to another around a ring, giving permission to the station possessing the token to send data frames. token passing The access method used on token ring networks. token ring A network topology and data signaling scheme in which a special data packet (called a token) is passed from one station to another along an electrical ring. A transmitting station takes possession of the token, transmits the data, then frees the token after the data has made a complete circuit of the electrical ring.
token ring network A baseband networking system that operates over shielded twisted-pair copper wires, using a ring topology and token passing access protocol. The original protocol developed by IBM was succeeded by the IEEE 802.5 standard for token ring network communications. Can be run at 4 Mb/s or 16 Mb/s. See also 802.5, Ethernet, LAN. TokenSpeedTM Bay Networks switching module for token ring networks with wire-speed switching. Part of the Centillion 100 family of switching products. topology The physical or logical arrangement of nodes on a network. Physical topology describes the physical relationships between nodes and links. Logical topology is the description of the possible logical connections between network nodes, indicating which pairs of nodes are able to communicate. LANs are usually configured in one of three topologies: star where devices are linked to a central point; ring where devices are connected in a closed loop; or bus where devices are attached to a linear, open-ended cable terminated at each end with a resistive load. TP Transaction Program. Transport Protocol. Twisted pair. A cable consisting of two sets of insulated 18- to 24-AWG (American Wire Gauge) wires twisted together to reduce electrical interference, with or without a shield under the outer insulation. TPE Twisted pair Ethernet. TP-PMD Twisted pair - physical medium dependent. The ANSI standard for running FDDI over UTP wire. Adopted by the IEEE 802.3 for use in 100BASE-TX applications. traffic filter A configuration file that lets an interface selectively handle specified network traffic (packets, frames, or datagrams). Using traffic filters, you can instruct a router to block, forward, log, or prioritize certain traffic. TrafficManTM Bay Networks tool included with Optivity Analysis software that assembles information gathered by multiple NMMs and presents the data in a traffic map to aid in identifying redundant links, traffic bottlenecks, and misconfigured internetworking devices. trailer Part of a packet (message data surrounded by a header and trailer) that carries special information used by the network to the destination station. transceiver Transmitter-receiver. An internal or external device for receiving and transmitting data; for example, an IEEE 802.3 medium attachment unit (MAU), through which Ethernet stations attach to the network cabling medium and which provides circuitry to convert signals between a form suitable for the network and a form suitable for the station. transceiver cable A cable used to connect a station's AUI port to a transceiver; also called AUI cable, drop cable, or transceiver drop cable.
transfer mode Aspects covering transmission, multiplexing, and switching in a telecommunications network. translation bridges (XB) Bridges between source routing networks (SRB) and transparent bridge networks. These bridges allow end stations using different bridging techniques to communicate as though they used the same bridging technique. See also transparent bridging (TB), SRB. translational device A device, such as a router, that connects dissimilar MAC-layer networks (Ethernet to FDDI, for example) together. All translational devices are store and forward. transmitter power The minimum peak power injected into an optical fiber by the transmitter. transparent bridging (TB) A system-level concept where the bridges perform MAC address learning and look-ups to determine whether or not a packet on a LAN must be forwarded to another segment. The bridging function is transparent to the end station because the end station does not need to know if the device it is addressing is on the same physical segment. All Ethernet bridges are transparent. transport layer Layer 4 of the OSI reference model, responsible for reliable end-to-end data transfer between end systems. Manages the transfer of data from a source program to a destination program. trap An alarm message that a monitored device sends to the management station whenever that device detects an alarm condition. Alarm conditions include device errors, network errors, status changes, and threshold values exceeded. TrendManTM Bay Networks software application that works with the Optivity network management application and collects and displays data showing long-term performance trends to aid in planning network expansion. Used to baseline Ethernet, token ring, and FDDI network performance. TRT Token rotation timer. A timer that controls FDDI ring scheduling during normal operation and detects serious ring errors. trunk A main or high-bandwidth communication cable between a telco central office and a PBX or between PBXs in different locations. trunk cable Cable that connects the ring in (RI) and ring out (RO) ports on token ring hubs in order to connect more than one hub to the token ring network. trunk link A link that connects two trunk ports. For Bay Networks modular and Fast Ethernet switches, trunk links can be either 100 Mb/s full-duplex or 200 Mb/s full-duplex, but not 10 Mb/s. trunk port An expansion port or attachment port used to connect two Bay Networks modular or Fast Ethernet switches.
TSO Time-sharing option. TTL Time to live. The TTL counter specifies the maximum number of hops that an IP data packet can traverse in the network before an intermediate router discards the packet, thus preventing packets from looping endlessly through the network. TTRT Target token rotation timer. Part of the FDDI token claim process. When the ring is initialized by stations inserting onto the ring, the TTRT of each frame is checked and the frame that contains the lowest TTRT wins the claim. Tunnel A virtual, direct pathway with which to transmit bidirectional traffic between two end points. See also VPN. tunneling A mechanism of forwarding traffic from remote users to a corporate network through an existing public IP network. Data is encapsulated within an IP datagram and then decapsulated at the other end point of the tunnel. See also BayDVSTM, GRE, VPN. tunnel management The establishment and tearing down of virtual (IP) tunnels, based on server and remote user information. See also TMS, VPN. TVX Valid transmission timer. In an FDDI network, the valid transmission timer is used to recover from transient ring errors. twisted pair A cable consisting of two sets of insulated 18- to 24-AWG (American Wire Gauge) wires twisted together to reduce electrical interference, with or without a shield under the outer insulation. Tx or Txd Transmit. RS-232-C hardware standard signal sending information from one device to another; also called TD. TX is also used to indicate the medium type, as in 100BASE-TX (indicating UTP connection). Type 1 cable A shielded twisted-pair cable used as distribution cable in the IBM Cabling System. See also IBM Cabling System. Type 2 cable A shielded twisted-pair cable used as distribution cable in the IBM Cabling System, the same as Type 1 cable with the addition of four voice-grade pairs. See also IBM Cabling System. Type 6 cable A flexible shielded twisted-pair cable used for patch cables or short-distance distribution cables in the IBM Cabling System. See also IBM Cabling System.
Type 8 cable A flat shielded twisted-pair cable used for under-carpet wiring in the IBM Cabling System. See also IBM Cabling System. Type 9 cable A thin shielded twisted-pair cable used as low-cost, short-distance distribution cable in the IBM Cabling System. See also IBM Cabling System. Type 66 block A connecting block used in telephone connections, typically consisting of an insulated base covered by four vertical columns of 50 insulation displacement or wire-wrap connectors; also called punchdown block, splice block, telco block, or wiring block. U-frame Unnumbered frame. UA Unnumbered acknowledgment. UART Universal asynchronous receiver/transmitter. An integrated circuit containing a transmitter and a receiver. UDP User Datagram Protocol. An efficient but unreliable, connectionless protocol that is layered over IP, as is TCP. Application programs are needed to supplement the protocol to provide error processing and retransmission of data. UDP is an OSI layer 4 protocol. UDP/IP User Datagram Protocol/Internet Protocol. A datagram transmission protocol implemented on top of the Internet Protocol. UI Unnumbered Information (frame). A logical link control (LLC) frame type on which LLC does not perform link-level error recovery. UID Unique Identifier (or Unique ID). UL Underwriters Laboratories. A nonprofit third-party safety testing and certification organization in the United States and North America. http://www.ul.com/ ULP Upper level protocol. Any protocol above IP or TCP in the layered protocol hierarchy that uses IP or TCP. Includes transport layer, session layer, presentation layer, and application layer protocols. UNA Upstream neighbor address. UNH-IOL University of New Hampshire Interoperability Lab. Site of FDDI TP-PDM (twisted-pair physical media-dependent) implementation interoperability testing.
UNI User-to-network interface. Generic term to indicate interfaces to both public or private frame relay or ATM networks.Typically end point devices such as client workstations, client servers, or ATM routers. The current UNI specification describes the signaling protocols that let users set up connections between ATM devices in customer premises equipment or public carrier equipment. The UNI specification includes support for switched virtual circuits. UNIX Operating system developed at Bell Labs, trademarked by UNIX Systems Lab, which is now owned by Novell. unnumbered links A method of connecting two LANs through a WAN, where the WAN end points do not have their own IP addresses. UPS Uninterruptable power supply. A battery backup system that provides continuous power in the event of power failure or fluctuation. upstream In a token-ring network, the direction from which data flows. A station detecting a ring failure upstream transmits (beacons) a special MAC frame used to isolate the location of the error. user name A string of letters, and possibly numbers, that identifies a user to the system. utilization The level of traffic over a communications channel. utilization rate The fraction of the capacity being used, expressed as a percentage. UTP Unshielded twisted pair (cable). A cable medium with one or more pairs of twisted insulated copper conductors twisted together to reduce electrical interference and bound in a single plastic sheath. Now becoming the most common method of bringing telephone and data to the desktop. See also STP. UUCP UNIX-to-UNIX Copy Program. Standard UNIX Utility/Communications Protocol. V.34 An ITU-TSS (international) standard (1994) for 28,800 b/s dial-up modems. Also known as "V.Fast." V.90 A 1998 ITU standard for 56K modem technology, downloading data at up to 56 Kb/s and uploading at 33.6 Kb/s. This standard requires the service provider (that is, POTS) to have a direct digital connection to the user line because the 56K digital signals are not converted to analog signals at the service end. See also ITU, K56flex, VersalarTM, x2. http://www.v90.com valid cell A cell in which the header is declared by the header error control process to be free of errors. valid transmission timer In an FDDI network, the valid transmission timer is used to recover from transient ring errors.
VAX Virtual Access Extended. A registered product of Digital Equipment Corporation. VBM Virtual buffer memory. Bay Networks network management mechanism for cell/packet buffering. VBR Variable bit rate. VBR service Variable bit rate service. A type of telecommunication service characterized by a service bit rate specified by statistically expressed parameters that allow the bit rate to vary within defined limits. VC Virtual circuit. A network service that provides connection-oriented service regardless of the underlying network structure. See also connection-oriented. Virtual channel. A concept used to describe unidirectional transport of ATM cells associated by a common unique identifier value. VCC Virtual channel connection. Link set up between any source and destination in the ATM network. VCI Virtual channel identifier, also virtual circuit identifier. Address or label contained in the ATM cell header to designate the virtual channel within the virtual path on the physical ATM link. VCU Versalar Configuration Utility. A Web-based, menu-driven, graphical user interface that configures and manages Bay Networks Versalar 5399 and 8000 Remote Access Concentrators (RACs). See also RACTM, VersalarTM. VersalarTM Bay Networks family of access products, including the Versalar 5000 Access Switch, Versalar Remote Access Concentrators (RACs), Versalar Cable Modem Termination System (CMTS), and Versalar Cable Modems (CMs). The Versalar 5000 Access Switch and RACs have x2 and K56flex configuration capabilities. Bay Networks Versalar cable modem products have DOCSIS-based interoperability for broadband services. See also CM, CMTS, DOCSIS, K56flex, RACTM, x2. VGTP Voice-grade twisted pair. A type of unshielded twisted pair wiring designed to carry voice signals; also called D-inside wire. VIA Vendor's ISDN Alliance. A nonprofit corporation formed by key ISDN vendors to address interoperability issues. See also ISDN. http://www.via-isdn.org/ VINES Virtual Network Systems. Banyan Systems' UNIX-based network operating system for enterprise networking. virtual channel link A means of unidirectional transport of ATM cells between the point where a virtual channel identifier (VCI) value is assigned and the point where that value is translated or removed.
virtual community A group of virtual LAN devices that are managed through software control as a single subset or virtual domain. virtualization The ability to separate the physical layout of a network and its devices from how people are organized into groups (known as logical configuration). The ability to reconfigure logical network end stations relates to the way workgroups interact rather than their physical location. virtual LAN assignment The act of configuring single end stations or groups of users to a specific virtual LAN. virtual LAN membership A policy set, based on the MAC address of the attached end user device, defining how a new or moved device is treated upon connection to a virtual network port. virtual network A network of devices that interact as if they were on a common network segment, regardless of their geographical proximity. virtual network segmentation Segmentation process utilized in Bay Networks Model 281xx switches wherein each port connects to a segment that is a single collision domain. Network management applications group multiple ports into a single broadcast domain, called a VLAN, and ports (or end stations attached to ports) are assigned to different broadcast domains using the network management application without physically reconfiguring the network. Virtual networking provides the benefits of physical segmentation, but with more flexibility for future network changes and growth. virtual path link The group of virtual channel links, identified by a common value of the virtual path identifier, between the point where the VPI value is assigned and the point where the VPI value is translated or removed. virtual routing A type of routing in which a single high-speed physical interface supports an arbitrary number of logical networks. virtual view A logical or simulated representation of actual entities, devices, or physical objects. Vision DesktopTM Bay Networks Global Enterprise Management (GEM) software application. Provides an expanded view graphical user interface to enable network managers to manage a wide variety of desktop devices that run the host resources MIB agent. See also AssetManagerTM. VLAN Virtual LAN. A logical group of user end stations, servers, and other network devices that appear to be on the same LAN, regardless of their physical location. VME VersaModule-Europe. Standard bus (ANSI/IEEE-1014, 1987) that served as a backplane for early Bay Networks routers such as the AFN, ALN, CN, FN, and LN. These early routers were also referred to as VME-based routers.
VNR Virtual Network Router/Routing. A router or device providing routing functions between two virtual networks, typically through ATM protocols and interfaces. VNR capability is provided by the Bay Networks ARE router, as well as by the Bay Networks Model 5782 module. See also ARE, ATM. VoIP Forum Voice over Internet Protocol Forum. An IMTC-sponsored forum defining and establishing open, consistent guidelines for devices performing telephony communications over IP data networks. See also IMTC. http://www.imtc.org/i/activity/i_voip.htm VP Virtual path. A concept used to describe unidirectional transport of ATM cells belonging to virtual channels that are associated by a common identifier value. VPC Virtual path connection. A connection of virtual path links that extends between the point where the virtual channel identifier values are assigned and the point where those values are translated or removed. VPI Virtual path identifier. Identifier contained in the ATM cell header to designate the virtual path on the physical ATM link. VPN Virtual private network. A wide area communications network provided by a common carrier that offers the appearance, functionality, and usefulness of a dedicated private network, but actually it shares backbone trunks among all customers as in a public network. It allows a private network to be configured within a public network. VT Virtual terminal. A universal terminal as referred to in the ISO Virtual Terminal Protocol. See also virtual terminal protocol (VTP). Virtual tunneling. Encapsulating data packets in a variety of protocols and tunneling them through an IP network, using the generic routing encapsulation (GRE)mechanism. See also VTP. VTAM Virtual telecommunications access method. An IBM protocol. VTOA Voice and Telephony Over ATM. An ATM Forum interoperability specification that addresses voice and telephony over ATM networks to the desktop. See also ATM, ATM Forum. VTP Virtual Terminal Protocol. An International Standards Organization (ISO) standard that describes the operation of a universal terminal so that any terminal can talk with any host computer. See also virtual terminal (VT). Virtual Tunneling Protocol. A draft IETF standard that allows various layer 2 and layer 3 protocols to be tunneled through an IP network. VTP specifies a mobile IP-like message exchange protocol to create and manage IP tunnel sessions dynamically. VTP uses the generic routing encapsulation (GRE) mechanism to encapsulate multiprotocol payload traffic. See also virtual tunneling (VT).
WAN Wide area network. A large (geographically dispersed) network, usually constructed with serial lines, that covers a large geographic area. A WAN connects LANs using transmission lines provided by a common carrier. See also LAN, WLAN. wire speed Transmission of data from device input to output at the same speed attainable through a straight segment of wire or optical fiber. Instantaneous transmission of data from input to output. wiring block A connecting block used in telephone connections, typically consisting of an insulated base covered by four vertical columns of 50 insulation displacement or wire-wrap connectors; also called punchdown block, splice block, telco block, or Type 66 block. wiring closet A central building or room where distribution cabling is switched, terminated, and routed and where voice and data communications equipment are located; also called communications closet, equipment room, or telecommunications closet. WLAN Wireless Local Area Network. Standard-supported radio frequency technology allowing users to connect portable PCs to campus LANs without the constraints of wire-based connections. Wireless adapters (access points) connect users to each other to create an independent WLAN, or to remote LANs to enable use of network resources. workgroup A collection of terminals or other devices in a single location. Similar to a cluster, a workgroup typically has 2 to 16 nodes. In the context of structured networking, workgroup is interchangeable with network. workgroup hub A small preconfigured hub, or concentrator, suitable for use by a cohesive group. workstation A personal computer or similar device that serves a single user. World Wide Web (WWW) Information accessible through the Internet, where sites are connected by hypertext links and are accessed through a Web browser application. wrap To electronically isolate a token ring module or port from the rest of the network, using the management station. x2 A 3Com proprietary implementation of the 56 Kb/s ITU V.90 standard. Bay Networks Versalar Remote Access Concentrators (RAC) have x2 capability. See also ITU, RACTM, V.90. X.25 A CCITT X-Series Recommendation concerning protocols for OSI layers 1, 2, and 3, governing connections to public data networks. A series of widely adopted recommendations governing connections to packet switching networks using virtual circuits. XATOM eXpandable ATM Output Modular Switch. A main component of the Centillion 1600 switch, equipped with a large-capacity buffer.
XB Translation bridges. Bridges between source routing networks and transparent bridge networks. These bridges allow end stations using different bridging techniques to communicate as though they used the same bridging technique. See also transparent bridging (TB), SRB. XID eXchange station IDentification. XMIT Transmit. XNS Xerox Network System. Protocol between the terminal and the router that allows network stations to use the files and peripherals of other computers as if they were local. Y2K Year 2000 Challenge and Compliance. An issue and subsequent compliances that arose as a result of previous programming of information technology products. Computer applications, systems, software, and hardware had not been specifically configured to accurately process date and time data related to transition from the 20th century to the 21st century. In order to save computer memory, programmers employed a 2-digit date field (that is, "98" for 1998). Using only 2-digit fields, the transition from 1999 to 2000 would be read as "99" to "00," which is illogical. Programmers and information technology experts have devised various solutions to this and related problems. Hardware, software, systems, and applications are now specifically required to accurately process and calculate date-related information into the 21st century. Bay Networks Year 2000 product compliance information may be found at http://www.baynetworks.com/year2000/. ZIP Zone Information Protocol. An AppleTalk protocol. zone 10 Mb/s 10 megabits per second. Data transmission speed over standard Ethernet (10BASE-T) networks. 100 Mb/s 100 megabits per second. Data transmission speed over Fast Ethernet (100BASE-T) networks. 1000 Mb/s 1000 megabits per second, also 1 gigabit per second (Gb/s). Data transmission speed over Gigabit Ethernet networks. See also 802.3z, Gigabit Ethernet. 1BASE5 IEEE 802.3 standard for 1 Mb/s baseband data transmission over two-pair unshielded twisted pair wiring; also called StarLAN. 10BASE2 IEEE 802.3 specification for 10 Mb/s Ethernet running over thin coaxial cable, also known as ThinNet or Cheapernet. The maximum cable segment length is 185 meters. 10BASE5 IEEE 802.3 specification for Ethernet running over thick, yellow coaxial cable at 10 Mb/s. Maximum cable segment length is 500 meters.
10BASE-F IEEE 802.3 standard for 10 Mb/s Ethernet running over fiber. It includes subgroups 10BASE-FL (asynchronous fiber, interoperable with FOIRL, greater link distances), 10BASE-FB (synchronous fiber, serial chains of repeaters), and 10BASE-FP (asynchronous fiber and passive star topology, not supported by Bay Networks). 10BASE-FB IEEE 802.3 specification for 10 Mb/s Ethernet running over fiber optic cable. 10BASE-FB utilizes a synchronous signaling method in support of backbone networks. 10BASE-FL IEEE 802.3 specification for 10 Mb/s Ethernet running over fiber optic cable. 10BASE-FL utilizes an asynchronous signaling method used in standard 10 Mb/s links between end stations and the network. 10BASE-T IEEE 802.3 specification for Ethernet running over unshielded twisted pair wire. 10BASE-T derives its name from a baseband network that transmits at 10 Mb/s over twisted pair wire. 100BASE-FX Part of the IEEE 802.3u (100BASE-T) Ethernet specification for 100 Mb/s transmissions over fiber optic cable, using the FDDI TP-PMD standard for the PMD (physical media dependent) portion. 100BASE-T2 IEEE 802.3 specification for 100BASE-T (Fast Ethernet) transmission over two pair Category 3, or better, voice-grade unshielded twisted pair cable. 100BASE-T4 Part of the IEEE 802.3u (100BASE-T) Ethernet specification for 100 Mb/s transmissions over four-pair Category 3, or better, unshielded twisted pair cable. Unlike 100BASE-TX and 100BASE-FX, 100BASE-T4 uses a different physical signaling method, 8B/6T, where 8 binary bits are transmitted in 6-bit ternary signals. 100BASE-TX IEEE 802.3u (100BASE-T) Ethernet specification for 100 Mb/s transmissions over two-pair Category 5, or better, unshielded twisted pair cable. 1000BASE-CX IEEE 802.3z specification defining a specific physical layer using two pairs of specialized balanced copper cable. 1000BASE-LX IEEE 802.3z specification defining a specific physical layer for long wavelength transceivers using two multimode or single-mode fibers. 1000BASE-SX IEEE 802.3z specification defining a specific physical layer for short wavelength transceivers using two multimode fibers. 1000BASE-X IEEE 802.3z specification addressing repeaters, 8B/10B encoding and physical layers, as associated with Gigabit Ethernet technology. 2B1Q Two binary, 1 quaternary signaling, associated with xDSL technologies.
4B/5B The symbol encoding method at the physical sublayer for FDDI, 100BASE-FX, and 100BASE-TX networks. In 4B/5B, 4-bit data streams are encoded as 5-bit code words. 8B/10B The symbol coding method at the PCS sublayer for fiber channels and 1000BASE-T, 1000BASE-SX, and 1000BASE-LX networks. The 8-bit data stream is encoded as a 10-bit code word. 80/20 rule A networking industry convention postulating that 80 percent of network traffic occurred on a single LAN, while 20 percent of traffic originated remotely and required routing, bridging, or switching services for access to other LANs.This rule is now considered outdated because of the proliferation of Internet technologies, corporate intranets, server consolidations, and a larger workforce accessing corporate LANs remotely. 802.x The set of IEEE standards for the definition of LAN protocols. See also IEEE. 802.1d The IEEE standard for inter-LAN bridges, usually Ethernet and token ring networks, which includes the Spanning Tree Protocol (STP) to prevent loops in redundant bridges. 802.1Q A draft IEEE standard for virtual bridged LANs. The draft addresses architecture, services, and associated algorithms and protocols for virtual bridged LANs. See also VLAN. 802.2 The IEEE standard that specifies the link layer control (LLC) portion of the data link layer (DLL) for various media access methods. See also DLL, LLC. 802.3 The IEEE standard for Ethernet networks. 802.3z An IEEE extension of the 802.3 standard, to address Gigabit Ethernet (1,000 Mb/s). It includes specifications for media access control (MAC) parameters, as well as physical layer, repeater, and management parameters for Gigabit Ethernet. See also Gigabit Ethernet. 802.5 The IEEE standard for token ring networks using the token ring passing access method on a ring topology. Copyright © 1998, Bay Networks, Inc. All rights reserved.
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