01-Overview-2.pdf

Data and Computer Communications Chapter 1 – Data Communications, Data Networks, and the Internet EIGHTH EDITION BY WILLIAM STALLINGS Data Communications, Data Networks, and the Internet The fundamental problem of communication is that of reproducing at one point either exactly or approximately a me...

Data and Computer Communications Chapter 1 – Data Communications, Data Networks, and the Internet EIGHTH EDITION BY WILLIAM STALLINGS Data Communications, Data Networks, and the Internet The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point - The Mathematical Theory of Communication, Claude Shannon Data Communications, Data Networks 3/23/2024 3 Prepared by Dr. J. VijiPriya Contemporary Data Comms trends ◦ traffic growth at a high & steady rate ◦ development of new services ◦ advances in technology significant change in requirements ◦ emergence of high-speed LANs ◦ corporate WAN needs ◦ digital electronics A Communications Model generates data converts data into Transmittable signals carries data from converts source to destinationreceived signal into data takes incoming data Communications Tasks Transmission system utilization Addressing Interfacing Routing Signal generation Recovery Synchronization Message formatting Exchange management Security Error detection and correction Network management Flow control Communications Tasks Con…  Key tasks are performed in Data Communication System transmission system utilization - need to make efficient use of transmission facilities typically shared among a number of communicating devices a device must interface with the transmission system once an interface is established, signal generation is required for communication there must be synchronization between transmitter and receiver, to determine when a signal begins to arrive and when it ends there is a variety of requirements for communication between two parties that might be collected under the term exchange management Error detection and correction are required in circumstances where errors cannot be tolerated Flow control is required to assure that the source does not overwhelm the destination by sending data faster than they can be processed and absorbed in destination 3/23/2024 PREPARED BY DR. J. VIJIPRIYA 7 Communications Tasks Con…  Key tasks are performed in Data Communication System Con.. addressing and routing, so a source system can indicate the identity of the intended destination, and can choose a specific route through this network Recovery allows an interrupted transaction to resume activity at the point of interruption or to condition prior to the beginning of the exchange Message formatting has to do with an agreement between two parties as to the form of the data to be exchanged or transmitted, such as the binary code for characters Frequently need to provide some measure of security in a data communications system Network management capabilities are needed to configure the system, monitor its status, react to failures and overloads, and plan intelligently for future growth 3/23/2024 PREPARED BY DR. J. VIJIPRIYA 8 Data Communications Model Transmission Medium selection is a basic choice ◦ internal use entirely up to business ◦ long-distance links made by carrier rapid technology advances change mix  Wired(e.g. fiber optic)  Wireless (e.g., satellite and radio). transmission costs still high hence interest in efficiency improvements Networking growth of number & power of computers is driving need for interconnection also seeing rapid integration of voice, data, image & video technologies two broad categories of communications networks:  Local Area Network (LAN)  Metropolitan Area Network (MAN)  Wide Area Network (WAN) Wide Area Networks spans a relatively large geographical area, consists of two or more LANs and MANs are often connected through public networks, such as the telephone system, Internet. connected through leased lines or satellites cross public rights of way rely in part on common carrier circuits alternative technologies used include: WANs have been implemented using following technologies :  circuit switching  packet switching  frame relay  Asynchronous Transfer Mode (ATM) Circuit Switching uses a dedicated communications path established for duration of conversation comprising a sequence of physical links with a dedicated logical channel eg. telephone network Packet Switching Data is sent in a sequence of small chunks (packets) at a time without need to dedicated communications path packets passed from node to node between source and destination used for terminal to computer and computer to computer communications Frame Relay packet switching systems have large overheads to compensate for errors Frame relay provides high data rates and low error rates on modern WAN links. modern systems are more reliable errors can be caught in end system Frame Relay provides higher speeds with most error control overhead removed Asynchronous Transfer Mode (ATM) ATM is culmination (result) of developments in circuit switching and packet switching  evolution of frame relay  Uses fixed packet (called cell) length with little overhead for error control  anything from 10Mbps to Gbps  Allows constant data rate using packet switching technique with multiple virtual circuits Local Area Networks smaller scope ◦ Building or small campus usually owned by same organization as attached devices data rates much higher switched LANs, eg Ethernet wireless LANs Metropolitan Area Networks MAN -middle ground between LAN and WAN spanning a city / metro area with higher speed connections private or public network high speed with large area The Internet Internet evolved from ARPANET ◦first operational packet network ◦applied to tactical radio & satellite nets also ◦had a need for interoperability ◦led to standardized TCP/IP protocols Internet Elements Internet Architecture Example Configuration Summary introduced data communications needs communications model defined data communications overview of networks introduce Internet