Course Objectives. Data communications play a key role in modern information systems. Objective of this course is to make students familiar with data communication technologies and how to use them to: Design Implement Operate Manage enterprise networks. Course Format. Formal lectures - PowerPoint PPT Presentation
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• Data communications play a key role in modern information systems.
• Objective of this course is to make students familiar with data communication technologies and how to use them to:– Design– Implement– Operate– Manage
• High speed networking• Wireless communications• Networking trends (futures)• LAN and WAN design• LAN and WAN case studies• Design and implementation Laboratory
• A computer network interconnects a variety of computing devices (end nodes) so that they may communicate with each other.– It consists of computing devices, transmission media
(communication channels) to transmit data and control signals, communication electronics for routing/switching data from sources to destination and the software for doing so.
– Networks may span small to large geographical areas (LANs, MANs, WANs).
• Bounded Media • Unbounded Media (air or a vacuum)- Twisted pair wire - AM and FM radio- Co-axial cable - TV broadcasting- Fiber optic cables - Satellite communication- Wave guides - Microwave radio
• Network electronic devices serve a variety of functions including routing or switching data from source to destination or for providing the interface between different transmission media or different communication protocols.
• Software in end nodes implements techniques and protocols which define the rules and end procedures for initiating and terminating data transfers, interpreting how data is represented and transmitted and how errors are handled.
• Software in the network electronics performs other functions to ensure data is transmitted from source to destination(s).
• Interface: the point of interaction between two devices such as a printer and a PC.
• Interconnection standards: specification of the methods of interfacing two devices, making it unnecessary for vendors to know the insides of each other’s equipment as long as the specifications at the boundaryare met.
• Architecture: blueprint of standards for a network consisting of items such as choice of media, media interfaces, encoding methods, transmission protocols, routing protocols, etc.
• Needed to ensure interoperability between various devices and equipment made by different vendors.
• Resource sharing (ending the tyranny of geography): making all programs, computing equipment and data available to anyone on the network without regard to the physical location of the resource and the user.
• High reliability:– Redundancy in hardware, software and the network
continue to make services available in a transparent way to the user even if some components fail. An airline can lose millions of $’s if its reservation system is not available 100% of the time.
– Networks also allow physical redundancy, ensuring continued service if a disaster strikes one location.
• Effective use of computer and communication technologies can:– Enhance business revenues– Reduce operating costs– Avoid costs by increasing people productivity– Create new business opportunities (ATM machine
networks, internet commerce etc.)– Provide a competitive edge (eg., SABRE reservation
• The TV network uses a combination of coaxial cable, satellite links, and electromagnetic propagation through air to transmit video (including voice) signals.
• The data network uses a variety of transmission media, including the voice and TV networks, to transmit data in the form of digital signals.
• Today voice and video are becoming increasingly digitized (digital phones, high resolution digital TV) and are increasingly transmitted by data networks.
• Ultimately all voice, video, and data will be digital and will be transmitted by digital (data) networks.
• The reason is that it is far more cost effective to build, operate and manage networks that use digital rather than analog signals. (eg., if the telephone network were built today, it would be an all digital network).
• Future data networks will interconnect multimedia devices capable of handling voice, video, and data.
Differences In CharacteristicsBetween Data And Telephone (Voice) Communication
Data Communication Voice Communication
• Desirable set-up time in one • One second to one minute second or less to set up a connection• One or two way transmission • Two way transmission in most cases• Data received is error free • Tolerant of noise and some
Differences In CharacteristicsBetween Data And Telephone (Voice) Communication (Cont.)
Data Communication Voice Communication
• Little or no redundancy in • Much inherent redundant information information• Transmission usually in • Transmit or receive bursts continuously until call is
disconnected• Data can be stored and • Not tolerant of transmission transmitted when convenient delays
Differences In CharacteristicsBetween Data And Telephone (Voice) Communication (Cont.)
Data Communication Voice Communication
• Transmission has high peaks • Transmission rate relatively Peak to average ratios as high constant as 1,000. • Connection may be required • Duration of connection for 24 hrs/day, 7 days/week usually limited to (eg., cash machine) several minutes
• Computer networking started to evolve in the early and mid 1960’s with the advent of timesharing.
• By 1970 timesharing machines supported networks of local and remote terminals.
• These early networks supported timesharing and remote batch processing.
• In the latter part of the 1970’s, computer to computer network connections were used for loadsharing and data interchange (eg., early electronic funds transfer).
• In the late 1970’s and early 1980’s, ARPA (Advanced Research Projects Agency) started to test networks for peer-to-peer computer communication and terminal support on a national scale.
• By the mid 1980’s this network became available to the universities and NSF (National Science Foundation) started funding university connectivity.
• Early applications of these networks included electronic mail, downloading large data sets (ftp) and remote access to computers (telnet).
• Companies such as Compuserve and America On Line began to provide a number of services using the internet, including providing internet connectivity to personal computers in people’s homes.
• Today, about 20 million workstations are connected to the commodity Internet and usage continues to increase, resulting in congestion at peak times of the day over many parts of the network.
• The increasing network congestion reduced the value of the Internet for new applications such as web-based distance education and low latency, high bandwidth connection to and among supercomputers.
• These applications require support for QoS (Quality of Service) not available on the current Internet.– eg., bandwidth reservation– low variance in latency to prevent jerkiness in video
• Consequently, leading research institutions are leading the development of Internet 2, a new high bandwidth network strictly for universities to avoid congestion due to commercial traffic and one that supports QoS functions required by multimedia and other applications.
• In general, the vast majority of today’s networks are store and forward networks in that stored data is forwarded from its source to its destination in a series of hops when it is convenient to do so.
• While the store and forward technique has several disadvantages (eg., it is difficult to transmit voice because the transmission delays are highly variable), it has the advantage that results in more affordable networks and it allows errors to be detected and corrected through retransmission.
• The store and forward concept makes it convenient for networks to be used for:– Exchanging electronic mail– Reading and posting to electronic bulletin boards– Accessing files and information anywhere in the network
(eg., library and web services)– Accessing unique hardware and software resources– Sharing of information (workgroup collaboration)
• Such applications provide users with access to needed information and resources when they are needed from wherever there is telephone or some other means of network access.
• This is changing how we play, work, communicate, teach, learn, and conduct business.
• They provide both new opportunities and new challenges.• These challenges will slow the deployment of networks to a
• Address space shortage. IP addresses are limited to 2**32 and efforts are underway to increase this to 2**128.– enterprises cannot use all 2**24 addresses allowed by a
class A license.– Class C addresses are more effective but they increase
the size of routing tables in routers, reducing the efficiency of packet forwarding.
• Decentralized control allows the network to easily scale.
• It also threatens to turn it into an anarchy where reliable service is not guaranteed. Security is also an issue.
• It also means there is no uniform way to do usage accounting, which is required to guarantee Quality of Service for emerging applications (eg., multimedia).
• Multimedia (voice, video, and data) applications need real-time performance guarantees such as a certain minimum bandwidth or bounded latency with small variance (jitter).
• These Quality of Service (QoS) performance parameters are not well supported with the current Internet technologies.
• QoS requires signaling to inform all routers in the path about the quality of service parameters for each class of traffic. New traffic streams must be allowed or denied entry to the network depending upon the current traffic streams and their QoS parameters.
• This is difficult to accomplish under decentralized network control.
• General High Usage Terms• Network Electronics Terms• Network Technology Terms• Computing Terms• Services and Application Terms• Standards Organizations• Popular Protocols• Operating Systems
• ATM - Asynchronous Transfer Mode. International Standard for cell relay in which voice, video, and data can be transmitted in fixed length 53 byte cells.
• Circuits, Channels, Trunks - Communication paths between two or more points.
• Frame Relay - Industry standard for handling multiple switched virtual circuits between connected devices.
• Packet Switching - Communication method in which nodes share bandwidth with each other by sending packets of data with source and destination addresses for proper routing
• Connectionless - Term used to describe data transfer without the existence of a virtual circuit
• Connection Oriented - Term used to describe data transfer that requires the establishment of a virtual circuit.
• Host - Computer (usually large system) connected to a network.
• End Systems - End-user workstations on a network.
• Workstation - A computing device used by a user to perform his / her work. Some people use the word to imply a device more powerful than a conventional personal computer.
• Client / Server - Distributed networked systems in which application responsibilities are divided into 2 parts - the client (front end) and the server (backend).
• Distributed Sytems - Distributed and networked systems• Rlogin - Remote login• FTP - File Transfer Protocol• Email - Electronic mail• News - News service
• ISDN - Integrated Services Digital Network. Communication protocol offered by phone companies which allows phone networks to carry voice, video, and data.
• CDPD - Cellular Digital Packet Data. Standard for 2-way wireless data communication over high frequency cellular phone channels.
• DQDB - Distributed Queue Dual Bus. Data link layer protocol designed for metropolitan area networks.