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Unformatted text preview: Data and Computer Communications Communications
Chapter 1 – Data Communications, Chapter Data Networks, and the Internet Data
Eighth Edition by William Stallings Lecture slides by Lawrie Brown Data Communications, Data Networks, and the Internet Networks, The fundamental problem of The communication is that of reproducing at one point either exactly or approximately a message selected at another point - The Mathematical Theory of Communication, Mathematical Claude Shannon Claude Contemporary Data Comms Contemporary trends traffic growth at a high & steady rate development of new services advances in technology emergence of high-speed LANs corporate WAN needs digital electronics significant change in requirements A Communications Model Communications Communications Tasks Communications
Transmission system utilization Addressing Interfacing Signal generation Synchronization Exchange management Error detection and correction Flow control Routing Recovery Message formatting Security Network management Data Communications Model Data Transmission Medium Transmission selection is a basic choice internal use entirely up to business long-distance links made by carrier fiber optic wireless rapid technology advances change mix transmission costs still high hence interest in efficiency improvements Networking Networking growth of number & power of computers is growth driving need for interconnection driving also seeing rapid integration of voice, also data, image & video technologies data, two broad categories of communications two networks: networks: Local Area Network (LAN) Wide Area Network (WAN) Wide Area Networks Wide span a large geographical area cross public rights of way rely in part on common carrier circuits alternative technologies used include: circuit switching packet switching frame relay Asynchronous Transfer Mode (ATM) Circuit Switching Circuit uses a dedicated communications path uses established for duration of conversation established comprising a sequence of physical links with a dedicated logical channel eg. telephone network Packet Switching Packet data sent out of sequence small chunks (packets) of data at a time packets passed from node to node packets between source and destination between used for terminal to computer and used computer to computer communications computer Frame Relay Frame packet switching systems have large packet overheads to compensate for errors overheads 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 Asynchronous ATM evolution of frame relay fixed packet (called cell) length with little overhead for error control anything from 10Mbps to Gbps constant data rate using packet switching constant technique with multiple virtual circuits technique Local Area Networks Local smaller scope Building or small campus usually owned by same organization as usually attached devices attached data rates much higher switched LANs, eg Ethernet wireless LANs Metropolitan Area Networks Metropolitan MAN middle ground between LAN and WAN private or public network high speed large area The Internet The 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 Internet Architecture Internet Example Configuration Example Summary Summary introduced data communications needs communications model defined data communications overview of networks introduce Internet ...
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- Spring '09