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Lecture 4a: Communication and Networking

Lecture 4a: Communication and Networking. CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology. Overview. Network standards and standardization bodies The ISO 7-layer reference model in general and its instantiation in TCP/IP

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Lecture 4a: Communication and Networking

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  1. Lecture 4a: Communication and Networking CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology

  2. Overview • Network standards and standardization bodies • The ISO 7-layer reference model in general and its instantiation in TCP/IP • Circuit switching and packet switching • Streams and datagrams

  3. Overview • Physical layer networking concepts • Theoretical basis • Transmission media • Standards • Data link layer concepts • Framing • Error control • Flow control

  4. Standards and Organisations- International: • ITU-T: International Telecommunications Union - Telecommunications Standardization Sector • Telephone and data communications • Formerly the CCITT • ITU-R: Radiocommunications Sector • Radio Frequencies • Formerly the CCIR

  5. Standards and Organisations- International: • ISO - International Standards Organisation for all communication types • IETF – Internet Engineering Task Force

  6. Standards and Organisations - American • ANSI: American National Standards Institute for data communications • EIA: Electrical Industries Association for interfaces, connectors, facsimile, media • IEEE: Institute of Electrical and Electronic Engineers specifically for 802 LAN standards • NIST: National Institute of Standards and Technology the all American equivalent to the ISO (of course!!)

  7. The OSI Stack • Proposed by the International Standards Organisation (ISO) and other standards bodies • Its a layered approach to network protocols involving encapsulation of packets at each level of the stack and the sub-layers

  8. The OSI Stack Application 7 Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  9. The OSI Stack Application 7 • End-to-end connections • Segments and reassembles data in proper sequence • Setup and teardown of “virtual circuits” (connection oriented) • Can ensure segment delivery with error correction, recovery and flow control Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  10. The OSI Stack Application 7 • Moves information to the correct address • Assembles and disassembles packets • Addresses and routes data packets • Determines the best path for moving data through the network Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  11. The OSI Stack Application 7 • It is up to the data link layer to detect and if necessary correct errors • This is typically done by breaking the bit stream into distinct frames Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  12. Data Link Layer Concepts • Methods of framing include • Character count • Start/end characters – character stuffing • Start/end flags – bit stuffing • Physical layer coding violations

  13. Data Link Layer Concepts • Error control • A noise burst on the line can destroy a frame completely • Identified by • Acknowledgements • Timeouts • Individual packets can be retransmitted • Flow control • Throttles the sender to a rate that allows the receiver to keep up and handle all traffic

  14. The OSI Stack Application 7 • The OSI physical layer is concerned with the transmission of bits on the network • The order of bits • Bit level error-checking • Electrical / mechanical characteristics Presentation 6 Session 5 Transport 4 Network 3 Data Link 2 Physical 1

  15. Network Transmission Media • To be propagated (sent) from one location to another, a signal must travel along a physical path • The physical path that is used to carry a signal between a signal transmitter and a signal receiver is called the "transmission medium"

  16. Network Transmission Media • There are two types of transmission media • Guided media • Unguided media

  17. Network Transmission Media • There 4 basic types of guided media: • Open wire • Twisted pair • Coaxial cable • Optical Fibre • Unguided media • RF propagation • Microwave • Satellite

  18. OSI Instantiation in TCP/IP • Another widely used reference model is the TCP/IP model

  19. Principles Used to Determine Layers • Level of conception • Accurately defined duty • Internationally standardised protocols • Minimal information flow across layer boundaries • Number of layers

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