Basic Teminology Networking

Introduction to Switches, Routers, Firewalls & Servers A network Switch is a small hardware device that joins multiple computers together within one local area network (LAN).

Technically, network switches operate at layer 2 (Data Link Layer) of the OSI model. Unlike Hubs, network switches are capable of inspecting data packets as they are received, determining the source and

destination device of each packet and forwarding them appropriately. Layer 2 switches are installed in the enterprise for high-speed connectivity between end stations at the data link layer. L2

switches act as IP end nodes for Simple Network Management Protocol (SNMP) management, Telnet, and Web basedmanagement.

Layer 3 switches are routers that do Layer 3 forwarding in hardware. Router is a more sophisticated network device than switch or a hub. Like hubs and switches, network routers are small, box-like

pieces of equipment to which multiple network computers are connected. Routers join multiple area networks (LANs and WANs) on the Internet or on a large corporate network. Routers for home

networks (often called broadband routers) join the home (LAN) to the Internet (WAN) for the purpose of Internet connectionsharing. Hubs or switches are not capable of joining multiple networks or sharing an Internet connection.

Cisco and Juniper are leaders in manufacturing of switches and routers.Cisco and Juniper are leaders in manufacturing of switches and routers. A blade server is a high-density server used in a clustering of servers that are dedicated to multiple task, such as:

File sharing, virtualization, clusteringWeb hosting, web page serving and cachingSSL encrypting of web communicationTranscoding of web page content for smaller displaysStreaming audio and video content

Blade servers can also manage to include load balancing and failover capabilities. Blade servers allow more processing power in less rack space, simplifying cabling and reducing power consumption and

management through a single interface. IBM & HP are the leaders in manufacturing of blade servers. Other competitors include Sun Microsystems, Dell and Cisco.

WAN Topologies WAN topologies consists of both LAN and WAN. The particular WAN topology will depend upon the number of

sites to connect, distance between the sites and existing infrastructure. Peer-to-Peer: WAN with single interconnection points for each location is arranged in a peer-to-peer topology

each one connected to another one through dedicated circuits. This topology is best option for organizationswith only a few sites and the capability to use dedicated circuits that are leased from a telecommunicationsprovider, such as an ISP.

Ring : In Ring WAN topology, each site is connected to two other sites so that the entire WAN forms a ringpattern. This architecture is similar to the ring LAN topology, except that a Ring WAN topology connectslocations rather than local nodes. The advantages of a Ring WAN over a peer-to-peer WAN are twin fold- asingle cable problem will not affect the entire network, and routers at any site can redirect data to anotherroute if one route becomes too busy.

Star: In Star WAN topology, a single site acts as the central connection point for several other sites which

Chapter 3: WAN Technologies

Star: In Star WAN topology, a single site acts as the central connection point for several other sites whichprovides separate routes for data between any two sites. Star WANs are more reliable than the peer-to-peerWAN or ring WAN and provides shorter data paths between any two sites.

Mesh: A mesh WAN topology has many directly interconnected nodes to its destination. If there is issue withany connection, routers can redirect data easily and quickly. Mesh WANs are the most fault-tolerant type ofWAN configuration because they provide multiple routes for data. Only drawback to a mesh WAN is the costfactor. To reduce cost implement partial mesh in which critical WAN nodes are directly interconnected andsecondary nodes are connected through star or ring topologies. Partial-mesh WANs are more practical thanfull-mesh WANs.

Tiered: Tiered WAN topologies is hierarchical hybrid topology. In a Tiered WAN topology, WAN sites connectedin a star or ring formations are interconnected at different levels with the interconnection points beingorganized into layers.

Layer 3 protocols- X.25, ATM, FR, ISDN,PPP, MPLS X.25 is a global standard found in older networks. X.25 had an original maximum transfer speed of 56Kbps later

increased to 64Kbps with the digital version. X.25 is a packet-switching technology. It uses different routes to get the best possible connection between the

sending and receiving device at a given time. As conditions on the network change, such as increased network traffic,so do the routes that the packets take. Each packet is likely to take a different route to reach its destination during asingle communication session. The devices that make it possible to use X.25 service are called packet assemblers/dissemblers (PADs). A PAD is required at each end of the X.25 connection.

Asynchronous Transfer Mode (ATM) is a cell-based switching protocol that uses asynchronous time-divisionmultiplexing that organizes digital data into 53-byte cell units. ATM differs from other technologies based on packet-switched networks (such as the Internet Protocol or Ethernet), in which variable sized packets/frames are used. ATMhas properties of both circuit switched and small packet switched networking, making it suitable for wide area datanetworking as well as real-time media transport.

Frame relay is WAN protocol that operates at Physical and Data link layers of the OSI model. FR works between DTEand DCE devices using packet switching and Permanent Virtual Circuits(PVC). The connection is identified by a DataLink Connection Identifier(DLCI)Link Connection Identifier(DLCI)

Integrated Service Digital Network (ISDN) is a digital service running over existing telephone networks. ISDN cansupport both data and voice simultaneously. ISDN provides upto 128Kbps with a PPP multilink connection tocorporate networks or internet.

PPP is a successor to SLIP, provides router to router and host to network connections over synchronous(ISDN) andasynchronous circuits(dial-up). It uses LCP to maintain the data link, authentication using either PAP or CHAP andcompression.

MPLS belongs to family of packet-switched networks, is highly scalable, protocol agnostic, data-carrying protocol. Inan MPLS network, data packets are assigned labels. Packet-forwarding decisions are made solely on the basis of thislabel, without the need to examine the packet itself, due to which end-to-end circuits across any type of transportmedium using any protocol can be created. This eliminates dependence on a particular Data Link Layer technology,such as ATM, FR, SONET or Ethernet and eliminate the need for multiple Layer 2 networks to satisfy different types oftraffic. Subscribers with different access links can be aggregated on an MPLS edge without changing their currentcircuit, as MPLS is independent of access technologies.

Need for IP addressing, Addressing classes

When TCP/IP was introduced in 1980, it had two level addressing scheme. IPv4 was introduced and offered adequate scalability.

IPv4 Address– 32 binary bits, four octets of 8-bits separated by a period.– Hierarchically organized

• Network ID, Host ID decided by address class and subnet mask.• 3 Address classes:

– Class A: 1 byte network, 3 bytes host (1-126, subnet mask:255.0.0.0)

Chapter 4: IP Addressing

– Class A: 1 byte network, 3 bytes host (1-126, subnet mask:255.0.0.0)– Class B: 2 bytes network, 2 bytes host (128-191, subnet mask:255.255.0.0)– Class C: 3 bytes network, 1 byte host (192-223, subnet mask:255.255.255.0)– Class D: (224-239, reserved for multicast)– Class E: (240-255, reserved)

• For example:– Class A address, 10.10.5.21

Class A – 127 possible networks, 16777214 hosts per network Class B --16384 possible networks, 65534 hosts per network Class C– 2097152 possible networks, 254 hosts per network

Public & private addressing

TCP/IP is the dominant protocol in the world. Most network applications and operating systems havebuild their applications/networks around TCP/IP, even if they do not require internet connectivity.

Internet host require globally unique IP address. However, private host that are not connected tointernet can use any valid address, as long as it is unique within the private network.

RFC1918 set aside the following three blocks of IP address for private addressing scheme.

Class A range- 10.0.0.0 to 10.255.255.255 CIDR prefix-10.0.0.0/8Class B range- 172.16.0.0 to 172.31.255.255 CIDR prefix- Class B range- 172.16.0.0 to 172.31.255.255 CIDR prefix-172.16.0.0/16

Class C range- 192.168.0.0 to 192.168.255.255 CIDR prefix-192.168.0.0/16

Rest of IP address not belonging to above three blocks of IP address falls under public IP addressingscheme.

Routing protocols & Routed protocols

What is a Routing Protocol ?It is language spoken by routers to exchange routing information Between the devices.Typically runs on the WAN.Examples are BGP, OSPF, SNMP, Telnet

Chapter 5: Routing and Switching fundamentals

What are Routed Protocols ?Language used by computer systems to talk to one another.Examples of Routed protocols are TCP/IP, Apple talk, Novell IPX

Static routing & Dynamic routing

Static routing is the process of manually entering routes into a device's routing table via aconfiguration file which is loaded when the routing device starts up.

In static routing, any route that is configured manually must be updated or reconfiguredmanually to fix or repair any lost connectivity.

Dynamic routing protocols are supported by IOS running on the routing device (the router),which dynamically learn network destinations and how to get to them and also advertise thosedestinations to other routers.destinations to other routers.

Dynamic routing will 'learn' the routes to all networks that are directly connected to thedevice. Also router will learn routes from other routers that run the same routing protocol.

Dynamic routing protocols learns 'best route' information and forward this information toother routers running the same routing protocol. This gives dynamic routing protocols theability to adapt to logical network topology changes, equipment failures or network outages'on the fly'.

Basics of Switching Switching is a technology that reduces congestion in Ethernet, Token Ring and Fiber Distributed

Data Interface (FDDI) LANs by various traffic management techniques.

Unlike Bridges used in homes/ small office, Switches connect LAN segments in large enterprisenetworks, reduces collision in domains as each switch port is in different collision domain andselectively forward traffic to the appropriate segments. This cause Switch to operate at muchhigher speeds than bridges and support various new functionality such as VLANs, Spanning TreeProtocol (STP), VTP, etc..

The most commonly used LAN media is Ethernet having maximum bandwidth of 10Mbps. FastEthernet(100Mbps), Gigabit Ethernet(1000Mbps) throughputs are also available in higher endswitches.

MAC address table is used to determine the segment on which a datagram needs to betransmitted, thereby reducing traffic on each segment.

Two different forwarding techniques in switching: store-and-forward switching and cut-throughswitching.

In Store-and-forward switching, an entire frame must be received before it is forwarded throughthe switch. Latency is relative to the frame size—the larger the frame size, the longer the delaythrough the switch.

Cut-through switching allows the switch to begin forwarding the frame when enough of theframe is received to make a forwarding decision. This reduces latency through the switch.

Hostname, Interface configuration, routing From the lesson learned till now, you should be able to do basic configuration on routers & switches. Cisco IOS is the operating system software that comes with Cisco routers. Junos is the operating system software that comes with Juniper

routers. Cisco IOS interface provides 6 basic modes of operation- User EXEC mode, Privileged EXEC mode, Global Configuration mode, ROM Monitor

mode, Setup mode, RXBoot mode. In User EXEC mode limited examination of router information is possible. Eg: Router> In Privileged EXEC mode, detailed examination, testing, debugging and file manipulation is possible. Eg. Router# Global configuration mode allows you to change high level router configuration. Router(config)# ROM Monitor mode is automatically entered if the IOS does not exist or the boot sequence is interrupted. Eg. > or rommon> In Setup mode, dialog box is provided to help out in router setup configuration. In RXBoot mode, helper software is present which helps in router boot, when it cannot find IOS image in flash. Eg: Router<boot> There are 5 different password that can be used for securing router: Enable Secret, Enable password, VTY password, AUX password, Console

password.

Chapter 6: Introduction to device configuration

password. Router(config)#enable secret <secret> Router(config)#enable password <password> Router(config)#line vty 0 4 Router(config-if)#login Router(config-if)#password <password> Router can be assigned a hostname by entering the following command at the global configuration prompt. Router(config)# hostname <router name> If no name is entered the default name “Router” will be used. Each interface can be assigned a description to help identify the interface. Router(config-if)#description <description name> To save configuration done in router: Router# copy run start (current configuration stored into NVRAM) Router# copy run tftp (current configuration uploaded to TFTP drive) To enable IP routing: Router(config)#ip routing Add static IP route with: ip route<network><mask> <address|interface> <mask> <admin distance> To enable IP on an interface- Router(config-if)#ip address <ip address><subnet mask>

Network Address Translation (NAT) & Port Translation (PAT) NAT as defined by RFC 1631 is the process of swapping inside local IP address with a globally

unique IP address in the IP packet header. NAT is used so that hosts that are privately addressed by RFC 1918 addresses can access the

internet. NAT translations can occur dynamically or statically. When an outside host sends a response, NAT does the following: A. Receives it B. Checks the current table of network address translations C. Replace the destination global IP address with original inside IP source. In a enterprise/ISP network if all the computer systems uses private IP addresses, then the NAT

router needs a very large set of globally unique IP addresses with Static NAT. Another option is Overloading of NAT pools. Overloading allows NAT to scale to support many

Chapter 7: Basic Security concepts

Another option is Overloading of NAT pools. Overloading allows NAT to scale to support manyclients with only a few public IP addresses.

Example: A network with three different hosts connects to a web server using TCP. The samenetwork will have three TCP connections from the same client. All six connections connect to thesame server IP address and same TCP port (80, the well-known port for web services). In eachcase, the web server differentiates between the various connections because their combined IPaddress and port numbers are unique.

The advantage of NAT is their capability to use Port Address Translation (PAT), which allowsmultiple inside address to map to same global address. NAT router keeps track of differentconversations by mapping TCP and UDP port numbers.

NAT overload can use more than 65,000 port numbers, allowing it to scale without needingmultiple global IP addresses.

Firewall

• Firewall is a system or group of systems that enforces an access control policybetween two or more networks.

• Firewall can block traffic and permit traffic using access control policy.• Firewall enforces policy, imposes the policy on everything behind it.• Firewall keeps unwanted traffic out of network, while still allowing users from inside

to communicate freely with the outside network.• Firewall are configured to protect against unauthenticated, unauthorized traffic into

entering inside network.• Firewall cannot provide protection of the network, if any internal system is connected• Firewall cannot provide protection of the network, if any internal system is connected

to any external system, directly bypassing the firewall.• Three types of firewalls: Network Layer, Application Layer and Hybrid firewalls.• Network Layer firewall is a router capable of examining the packet headers traversing

through them.• Application layer firewalls are hosts running proxy servers, which permit no traffic

directly between networks.

Summary From these lessons, you should have learned Fundamentals of networking How to do basic configuration on routers.

Voice

Typical Telecom Network

The main elements of a Telecom Network are:

Switching Centers Nodes in the network. Routes the call (Switches) in the

Network Transmission

Links in the network.Links in the network. Provides the connectivity in the

network. End Equipments

User’s interface to the network. Customer Premises equipment.

Voice – How it is carried

• Analog VoiceElectrical signal varies one to one with voice signal on a continuous basis. More susceptible to noise

• Digital Voice– Sampling– Quantizing– Encoding– Encoding– Transmitting– Switching– Receiving– Decoding– Reconstruction (D to A conversion)

Voice Coding

Analog signal is converted to Digital using PCM

To transmit voice in a digital medium such as a 2.048 Mbit/s line, the analog voice signal needs tobe transformed into a binary format, then converted into a bit stream suitable for digitaltransmission.Sampling/ Nyquist Theorem:Sampling/ Nyquist Theorem:A signal must be sampled at a minimum of twice its maximum frequency in order to be reconstructed in ananalog format without major loss of information.

For voice signals, a maximum frequency of 4000 Hz provides adequate clarity and contains themajority of the information while conserving transmission bandwidth. Thus, a 4000 Hz voice signal mustbe sampled at at least 8000 samples per second. Each amplitude value (sample) is expressed as a 13-bitcode “word". An 8-bit byte is formed by comparing the sample to a "companding characteristic", which isa non-linear formula.

Internationally, a companding characteristic known as "A-law" is used, intended to provide optimum signal-to-noise performance over a wide range of signal levels.In North America, encoding is done according to the “μ-law”.These 8-bit words occur 8000 times per second for the 64 kbit/s digital bit stream. Data is generallytransmitted at a rate of 64kbit/s. Recommendation G.703 provides requirements for different interfaces. Foreach direction of transmission, three signals can be carried across the interface: 64kbit/s information, 64 kHztiming, and 8 kHz timing. The 8 kHz timing signal is not mandatory.

Access Network

OTE

NTE

EXTERNAL INFRASTRUCTURE - PHYSICAL MAKEUP

JOINT

BOX

PCP/SCP

DP

CABLE

CHAMBER

Access Node CUSTOMER PREMISES

DP

JOINT

`E`SIDE

JOINT

`D`SIDE

OFF

MDF

INTERMEDIATE

ELECTRONICS

ASDH

NTE

OTE

DSLAM

WDM

PAIRGAIN

ETC.

SPLITTER

PAIR GAIN

LINE OF SIGHT

RADIO ANTENNA

RTE

BLOWN

FIBRE &

TUBE

LINE LENGTH

LINE CHARACTERISTICS= COPPER

= FIBRE

SPLICE

PRIMARY

DUCT

TPON

SECONDARY

DUCT

Access network is the part of the telecom network which is closest to the customer.It starts from the switch and includes the access nodes.The main advantages of the access nodes are multiplexing, consolidating the traffic.The link between the switch and the access node is fibre , so quality of the signal is better with the access node.The media between the access node and the customer could be copper, fibre, or coaxial cable or wireless.

Switches

Switches perform the function of call routing Various types of exchanges are:

Manual -Human intervention required at most stages.High dependency on efficiency of personnel.Difficult to manage as number of subscribers and the traffic handled by the

exchanges increased.Step by step – Electromechanical (Strowger exchange and Cross bar)Switching is through lots of moving parts responding to electrical signals. Use some

basic circuitry for operational control Electronic Electronic

All the functions of the early day operator are performed by computers with help ofStored Programs.

Offers a wide range of services Contains the user’s service information.Contains the network rerouting informationProvides the path for information flow.Sets up and monitor the calls

Basic purpose of the switch is to switch over the voice of one person to another.– Call Setup and Routing– Call Supervision– Operations and Maintenance– Records call data for Billing Information

• Perform Line testing if required.• Has intelligence in form of programmed

tables.• Determine where the call should go (

routing tables )• Find the optimum route to destination• Actual switching of calls across different

switching equipments• Service to subscribers as per pre-decided

classes. Eg whether the customer is entitledto certain services or not ( service tables )

• Basic Components– Switching Module– Administrative Module– Communication Module

• Switch Vendors and equipment models– Lucent - 5ESS– Siemens – EWSD– Alcatel – OCB– Fujitsu – Fetex– Nortel – DMS to certain services or not ( service tables )

• Maintain records of calls• This provides the man machine interface

whereby the configuration of the Switch canbe altered

• Add / modify information in tables• Change class of service• Put in new lines or trunks• Remote diagnosis and maintenance of the

Switch• Monitor traffic

– Nortel – DMS– Ericsson - axe

• Some more functions are:• When the user lifts the receiver, issue a dial

tone• Sense the digits of the dialed number• For incoming calls, sense the called number

and check if the called party is busy• Issue ring to the called party• From exchange to subscriber’s premises,

ensure that the received call is routed to thecorrect subscriber.

Switching Topologies

• Class 1 Exchanges were internationalgateways - handing off and receiving trafficfrom outside the country

Class 2 Exchanges were tandem exchangeswhich interconnected whole regions of the

network.

Class 3 Exchanges were tandem exchangesconnecting major population centres withinparticular network.

1 1

2 2

3 3 3 3

Class 4 Exchanges were tandem exchangesconnecting the various areas of a city ortowns in a region.

Class 5 Exchanges were those to which end-users telephone lines would connect.

4 4 4 4 4 4 4 4

5 5 5 5

Signaling Signaling is the control information exchanged between two

network elements. During the call signaling comes into pictureat the following stages Initiation of the call, eg, going off hook, dialing the

number During the call, checking the credit limit Ending the call, releasing all resources

Types CAS ( Channel associated signaling, In band Signaling) CCS (Common Channel Signaling, Out of band signaling) Line or Subscriber Signaling Trunk Signaling

Common Channel Signaling (CCS)

Channel Associated Signaling (CAS)Voice & signaling share the same path

Voice & Signaling

Common Channel Signaling (CCS)Voice & signaling carried on separate facilities

Common Channel Signaling (CCS) Signaling is carried in a separate channel, hence the

term “out-of-band” signaling Uses “common” signaling channel for many lines

SS7 - used worldwide ISDN - used worldwide DASS 2 - used in the UK

Information carried as messages in packet form A major advantage of CCS is that one signaling link supports

many trunks (transmission paths between switches). Thisstresses the need for reliability. If one link crashes, manyroutes are out of service. Thus, redundancy is a key element ofsignaling systems.

Voice

Signaling

SS7

• SS7 is the currently prevalent type in signaling

The SS7 protocols have been developed by AT&T since 1975 anddefined as standard by ITU-T during 1981 in ITU-T's Q.7XX-seriesrecommendations. SS7 was designed to replace Signalling System#5 (SS5), Signalling System #6 (SS6) and R2, all of which are ITUstandards defined by ITU-T prior to SS7 and were once inwidespread international use. SS7 has substantially replaced SS6,SS5 and R2, with the exception that R2 variants are still used innumerous nations. SS5 and earlier used in-band signaling, wherethe call-setup information was sent by playing special tones intothe telephone lines (known as bearer channels in the parlance ofthe telecom industry). This led to a number of security problemsthe telecom industry). This led to a number of security problemswhen users discovered on certain telephone switching equipmentthat they could play these tones into the telephone handset andcontrol the network even without the "special keys" on anoperators handset. So-called phreakers experimented withfooling the telephone exchanges by sending their own user-generated signaling tones from small electronic boxes known asblue boxes. Modern designs of telephone equipment thatimplement in-band signaling protocols explicitly keep the end-user's audio path—the so-called speech path—separate from thesignaling phase to eliminate the possibility that the MF tones usedfor signaling are introduced by the end-user, which defeats theblue-box phreaking technique.

• SS7 moved to a system in which the signaling information wasout-of-band, carried in a separate signaling channel. Thisavoided the security problems earlier systems had, as the enduser had no connection to these channels. SS6 and SS7 arereferred to as so-called Common Channel Interoffice SignallingSystems (CCIS) or Common Channel Signaling (CCS) due to theirhard separation of signaling and bearer channels. However italso required a separate channel dedicated solely to signaling,but due to the rapid rise in the number of available channels atthe same time this was a moot point.

• There are two essential components to all telephone calls. Thefirst, and most obvious, is the actual content—our voices, faxes,modem data, etc. The second is the information that instructstelephone exchanges to establish connections and route the“content” to an appropriate destination. Telephony signaling isconcerned with the creation of standards for the latter toachieve the former. These standards are known as protocols.SS7 or Signaling System Number 7 is simply another set of

• To understand SS7 we must first understand something of thebasic inefficiency of previous signaling methods utilized in thePublic Switched Telephone Network (PSTN). Until relativelyrecently, all telephone connections were managed by a varietyof techniques centered on “in band” signaling.

• A network utilizing common-channel signaling is actually twonetworks in one:

1. First there is the circuit-switched "user" network whichactually carries the user voice and data traffic. It provides aphysical path between the source and destination.

2. The second is the signaling network which carries the callcontrol traffic. It is a packet-switched network using a commonchannel switching protocol.

• The original common channel interoffice signaling protocolswere based on Signalling System Number 6 (SS#6). Today SS#7 isbeing used in new installations worldwide. SS#7 is the definedinteroffice signaling protocol for ISDN. It is also in common usetoday outside of the ISDN environment.SS7 or Signaling System Number 7 is simply another set of

protocols that describe a means of communication betweentelephone switches in public telephone networks. They havebeen created and controlled by various bodies around theworld, which leads to some specific local variations, but theprincipal organization with responsibility for their administrationis the International Telecommunications Union or ITU-T.

• Signalling System Number 7 (SS#7 or C7) is the protocol used bythe telephone companies for interoffice signaling. In the past,in-band signaling techniques were used on interoffice trunks.This method of signaling used the same physical path for boththe call-control signaling and the actual connected call. Thismethod of signaling is inefficient and is rapidly being replaced byout-of-band or common-channel signaling techniques.

today outside of the ISDN environment.• The primary function of SS#7 is to provide call control, remote

network management, and maintenance capabilities for theinter- office telephone network. SS#7 performs these functionsby exchanging control messages between SS#7 telephoneexchanges (signaling points or SPs) and SS#7 signaling transferpoints (STPs).

• The switching offices (SPs) handle the SS#7 control network aswell as the user circuit-switched network. Basically, the SS#7control network tells the switching office which paths toestablish over the circuit-switched network. The STPs route SS#7control packets across the signaling network. A switching officemay or may not be an STP.

SS7 Protocols• The SS7 network is an interconnected set of network elements

that is used to exchange messages in support oftelecommunications functions. The SS7 protocol is designed toboth facilitate these functions and to maintain the network overwhich they are provided. Like most modern protocols, the SS7protocol is layered.1 Physical Layer (MTP-1)

• This defines the physical and electrical characteristics of thesignaling links of the SS7 network. Signaling links utilize DS–0channels and carry raw signaling data at a rate of 56 kbps or 64kbps.2 Message Transfer Part—Level 2 (MTP-2)

• The level 2 portion of the message transfer part (MTP Level 2)provides link-layer functionality. It ensures that the two endprovides link-layer functionality. It ensures that the two endpoints of a signaling link can reliably exchange signalingmessages. It incorporates such capabilities as error checking,flow control, and sequence checking.3 Message Transfer Part—Level 3 (MTP-3)

• The level 3 portion of the message transfer part (MTP Level 3)extends the functionality provided by MTP level 2 to providenetwork layer functionality. It ensures that messages can bedelivered between signaling points across the SS7 networkregardless of whether they are directly connected. It includessuch capabilities as node addressing, routing, alternate routing,and congestion control.4 Signaling Connection Control Part (SCCP)

• The signaling connection control part (SCCP)provides two major functions that are lacking inthe MTP. The first of these is the capability toaddress applications within a signaling point. TheMTP can only receive and deliver messages from anode as a whole; it does not deal with softwareapplications within a node.

• While MTP network-management messages andbasic call-setup messages are addressed to a nodeas a whole, other messages are used by separateapplications (referred to as subsystems) within anode. Examples of subsystems are 800 callprocessing, calling-card processing, advanced

• 6 Transaction Capabilities Application Part (TCAP)• TCAP defines the messages and protocol used to

communicate between applications (deployed assubsystems) in nodes. It is used for databaseservices such as calling card, 800, and AIN as wellas switch-to-switch services including repeatdialing and call return. Because TCAP messagesmust be delivered to individual applications withinthe nodes they address, they use the SCCP fortransport.

• 7 Operations, Maintenance, and AdministrationPart (OMAP)OMAP defines messages and protocol designed toprocessing, calling-card processing, advanced

intelligent network (AIN), and custom local-areasignaling services (CLASS) services (e.g., repeatdialing and call return). The SCCP allows thesesubsystems to be addressed explicitly.

• 5 ISDN User Part (ISUP)• ISUP user part defines the messages and protocol

used in the establishment and tear down of voiceand data calls over the public switched network(PSN), and to manage the trunk network on whichthey rely. Despite its name, ISUP is used for bothISDN and non–ISDN calls. In the North Americanversion of SS7, ISUP messages rely exclusively onMTP to transport messages between concernednodes.

• OMAP defines messages and protocol designed toassist administrators of the SS7 network. To date,the most fully developed and deployed of thesecapabilities are procedures for validating networkrouting tables and for diagnosing link troubles.OMAP includes messages that use both the MTPand SCCP for routing.

Erlang : Traffic is measured in the Unit called Erlang.

Calculations of Erlang:

One Time Slot /Circuit/Channel, continuously occupied for one hour constitutes 1 Erlang.In general the traffic per circuit has been taken for calculation as 0.7 Erlang1 Channel = 0.7 Erlang1 E1 = 21 Erlang ( 30 Channels *0.7 )Which means an E1 is dimensioned to carry the traffic of only 21 Erlang.For 10 E1’s 210 Erlang, 20 E1’s 420 Erlang and so on.

Traffic Engineering Basics- Erlang

For 10 E1’s 210 Erlang, 20 E1’s 420 Erlang and so on.

Common Terms in Erlang Calculation :

In Normal practice we define the volume of Traffic carried in terms ofMilli Erlangs & Deci-Erlangs since it will be ease for calculation .To convert Milli Erlang to Erlang just divide the value by 1000.To convert Deci-Erlang to Erlang divide the Value by 10.

NGN

SS7

MGC

SS7STP

Called Party

SS7STP SwitchSwitch

Calling Party

MGW MGW

Next Generation Network(NGN) is the next stage in the evolution of switches from circuitswitching to packet switching.A Packet-based network able to provide telecommunication servicesAble to make use of multiple broadband, QoS-enabled transport technologiesDecomposed architecture with service-related functions independent from underlyingtransport-related technologies.

* MGC – Media Gateway Control* STP – Signalling Transfer Point* H.248 – Signalling between MGC and MGW

NGN Network

A Soft switch (i.e. call agent, call server ormedia gateway controller) is a softwarebased switching & control solution thatruns on industry standard open platformsto provide the functionality of a traditionalTDM switch in modular, distributedfashion.

VoIP (voice over IP - that is, voice delivered

Advantages of NGN Network Avoids the need to install a switch in each location.

Instead a Media Gateway is installed serving thepurpose of Point Of Presence(POP).

Uniformity is achieved in configuration, databasemanagement, hardware maintenance by theinstallation of centralized soft-switch at any desiredlocation.

Drastic reduction in the floor space required for aswitch.

Redundancy can be achieved by coming up withanother soft-switch at another geographical location

.

VoIP (voice over IP - that is, voice deliveredusing the Internet Protocol) is a term usedin IP Telephony for the delivery of voiceinformation using the Internet Protocol(IP). In general, this means sending voiceinformation in digital form in discretepackets rather than in the traditionalcircuit-committed protocols of the publicswitched telephone network (PSTN).

another soft-switch at another geographical location More voice calls can be carried within a lesser

bandwidth compared to circuit switching through thepacketisation of the TDM voice calls to voice packets.

This results in a significant reduction in theoperational expenditure thus by increasing therevenues.

Dynamic call routing is possible through the inclusionof routers into the architecture.

Advanced GUI enables quick, convenient andeffective interface with the MGC and the MGWs.

GSM

Global System for MobileCommunicationsIt is a wireless method for providingtelephony services, along with dataservicesMain components of the network are:MSC and BSSFrequency bands used are 900 MHzand 1800 MHz and the channelseparation is 200 KHzGaussian Minimum Shift Keying GMSKis the modulation technique.

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSCBSCis the modulation technique. BSC

A interface

PSTN

GSM Components

• Mobile services Switching Center (MSC)• Base Station Controller (BSC)• Base Transmission Station (BTS)• Home Location Register (HLR)• Visitor Location Register (VLR)• Authentication Centre (AuC)• Equipment Identity Register (EIR)

Mobile services Switching Center (MSC)• MSC is the central component of the network subsystem. The

MSC performs the telephony switching functions for the mobile network. It controls calls to and from other telephony and data systems, such as the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), public data networks, private networks and other mobile networks. It is connected to BSS via A-interface. Gateway functionality enables an MSC to contact a network’s HLR in order to route a call to a Mobile Station (MS). Such an MSC is called a Gateway MSC (GMSC). MSC BTS BTS BTS BTS BTS BTS BTS BTS BSCBSCA interface

• MSC connectivity with BSS• Home Location Register (HLR)• Home Location Register (HLR)

The HLR is a centralized network database that stores and manages all mobile subscriptions belonging to a specific operator. Call routing and roaming capability is provided by the MSC in association with HLR and VLR. It acts as a permanent store for a person’s subscription information until that subscription is canceled. The information stored includes:· Subscriber identity· Subscriber supplementary services· Subscriber location information· Subscriber authentication informationThe HLR can be implemented in the same network node as the MSC or as a stand-alone database. If the capacity of a HLR is exceeded by the number of subscribers, additional HLRs may be added.

• Visitor Location Register (VLR)Information about all the mobilesubscribers currently located in an MSCservice area is stored in the VLR database..Thus, there is one VLR for each MSC in anetwork. A VLR may be in charge of one ormore MSCs areas. The VLR temporarilystores subscription information so thatthe MSC can service all the subscriberscurrently visiting that MSC service area.The VLR can be regarded as a distributedHLR as it holds a copy of the HLRinformation stored about the subscriber.

• Authentication Center (AUC)The main function of the AUC is toauthenticate the subscribers attemptingto use a network. It stores an identity keyfor each mobile subscriber registered withthe associated HLR. In this way, it is usedto protect network operators againstfraud. The AUC is a database connected tothe HLR, over an interface denoted the H-interface , which provides it with theauthentication parameters and cipheringkeys used to ensure network security.Equipment Identity Register (EIR)

When a subscriber roams into a new MSCservice area, the VLR connected to thatMSC requests information about thesubscriber from the subscriber’s HLR. TheHLR sends a copy of the information tothe VLR and updates its own locationinformation. When the subscriber makes acall, the VLR will already have theinformation required for call set-up.

Equipment Identity Register (EIR)The EIR is a database that contains one orseveral databases which store(s) the IMEIsused in the GSM system. This helps toblock calls from stolen, unauthorized, ordefective MSs. The mobile equipment maybe classified as "white listed", "grey listed"and "black listed" and therefore may bestored in three separate lists. It should benoted that due to subscriber-equipmentseparation in GSM, the barring of MSequipment does not result in automaticbarring of a subscriber.

Thank You!