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Networks are about Communication!

Networks are about Communication!. What is a good model of communication?. A COMMUNICATION MODEL. DATA COMMUNICATION NETWORK. comm.net. comm net node. net station i.e computer terminal or telephone. DATA COMMUNICATION NETWORKS. Communication networks. switched unswitched.

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Networks are about Communication!

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  1. Networks are about Communication! • What is a good model of communication?

  2. A COMMUNICATION MODEL

  3. DATA COMMUNICATION NETWORK comm.net • comm net node net station i.e computer terminal or telephone

  4. DATA COMMUNICATION NETWORKS Communication networks switched unswitched

  5. DATA COMMUNICATION NETWORKS Switched Packet Switched Circuit Switched

  6. DATA COMMUNICATION NETWORKS Unswitched(broadcast nets) packet radio satellite local • Packet switched nets are store and forward nets.

  7. DATA COMMUNICATION NETWORKS ckt switched nets have dedicated communication paths (i.e. telephone) For example: A Broadcast Comm. Net can be WAN, the media is unshared

  8. DATA COMMUNICATION NETWORKS Dish LAN EXAMPLES:

  9. DATA COMMUNICATION NETWORKS Ethernet with a bus topology:

  10. DATA COMMUNICATION NETWORKS Ring topology net: Note: No switching nodes ,media is shared in LAN For packet radio,every station can hear every other, the media is shared so this is a LAN technology

  11. DATA COMMUNICATION NETWORKS Agent input device transmitter channel channel receiver output device This course addresses the communication systems parts between the input and output devices.

  12. Computer Communications Architecture The Three Layer Model Application run on computer which use networks • network layer - xchange of data between computer • and network • transport layer - error detection and correction • application layer - file xfer etc.

  13. Computer Communications Architecture

  14. Protocol Data Units • TPDU1 = transport protocol data unit := transport hdr, chunk1 • TPDU2 = transport hdr, chunk2 • NPDU = network protocol data unit network hdr, TPDU

  15. Protocol Data Units • Application data = chunk1 + chunk2 + ... • Destination SAP (service access points) • TPDU has destination SAP so that appropriate application obtains data

  16. Protocol Data Units • Sequence # TPDU’s may be sent in any order,and by different routes and may arrive at different times. • TPDU may have error detection or correction • codes built-in • NPDU • destination address (i.e. IP address) • facilities requires (i.e. priority)

  17. Transmission Terminology • point-to-point :- guided transmission is unshared I.e. O(N**2) connectivity (completely connected) = number of links

  18. Transmission Terminology Multipoint guided transmission allows shared medium

  19. Transmission Terminology ANSI Defs: • simplex - one direction only • half-duplex - two-way but not at the same time. • full-duplex - simultaneous two way transmission

  20. Transmission Terminology • CCITT • CCITT vs ANSI • simplex = half-duplex • duplex = full-duplex • CCITT = international telegraph and telephone consultive committee

  21. Analog and Digital Data Transmission • data - entities which convey meaning • signals - encoding of data • signaling - act of sending a signal • transmission - communication of data by propagation and processing of signals

  22. Analog and Digital Data Transmission • digital data - takes on discrete values, i.e. text integers. • analog data - takes on continuously varying patterns of intensity, i.e.. sound But what is digital? What is Analog? How do we defines these things?

  23. Analog and Digital Data Transmission s(t) is continuous (i.e. analog) iff for all a

  24. DATA and SIGNALS • Modem (modulator/demodulator) modulation involves two waveforms: The modulating signal (the message) and the carrier wave which is altered by the modulating signal • The complementary process is called demodulation Bits <-> modem <-> analog signal <-> modem <-> bits

  25. ISO-OSI Model • ISO= International Standards Organization • OSI = Open Systems Interconnection • OSI Model = a 7 layer model used to describe most networks today

  26. 1. Physical Layer • This is a physical connection between machines. BITS

  27. 2. Data Link Layer • Provides reliable transfer of information across the physical links. FRAMES/Packets or DLPDU

  28. 3. Network Layer • Routing

  29. 4. Transport Layer • error recovery and flow control

  30. 5. Session Layer • Control for communication, close and open connections

  31. 6. Presentation Layer • Data formatting and character code conversion

  32. 7. Application Layer • file transfer, • virtual terminals, electronic mail • etc..

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