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Chapter Objectives

Chapter Objectives. After completing this chapter you will be able to: Describe in detail the following Local Area Network (LAN) technologies: - 802.3 Ethernet - 802.5 Token Ring - Fibre Distributed Data Interface (FDDI) - Wireless LAN. LAN Protocols. Ethernet.

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Chapter Objectives

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  1. Chapter Objectives After completing this chapter you will be able to: • Describe in detail the following Local Area Network (LAN) technologies: - 802.3 Ethernet - 802.5 Token Ring - Fibre Distributed Data Interface (FDDI) - Wireless LAN

  2. LAN Protocols

  3. Ethernet Ethernet is one of a family of network architectures governed by a protocol called Carrier Sense Multiple Access/Collision Detect (CSMA/CD). This type of network follows the Institute of Electrical and Electronic Engineers (IEEE) standard 802.3

  4. CSMA/CD Carrier Sense Multiple Access Collision Detect ListenWaitSend & Listen Access All Terminals Detect Calculate Send

  5. Ethernet Access Media

  6. Ethernet Hubs There are two kinds of hub: • Repeater hubs - Each port of a repeater hub links individual Ethernet media segments together to create a larger network that operates as a single Ethernet LAN. • Switching hubs - This kind of hub provides packet switching, typically based on bridging ports. Each port of a packet switching hub provides a connection to an Ethernet media system that operates as a separate Ethernet LAN. Unlike a repeater hub whose individual ports combine segments together to create a single large LAN, a switching hub makes it possible to divide a set of Ethernet media systems into multiple LANs that are linked together by way of the packet switching electronics in the hub.

  7. Components in an Ethernet System

  8. Twisted-Pair Media System

  9. Ethernet Frame Format Number of bytes: 7 1 6 2 4 6 46-1500 S O F Destination Address Source Address FCS Data Preamble Type SOF = Start of frame Minimum frame size = 64 bytes FCS = Frame check sequence Maximum frame size = 1518 bytes

  10. MAC Addressing There are two, MAC Layer addresses in an Ethernet frame. The first is the address of the source device and the second is the intended destination device. Each address consists of 48 bits, or 12 hexadecimal digits, which are typically denoted by six, two-digit hexadecimal numbers: 00-80-2C-00-19-20 The first six digits (high order) identify the manufacture and the last six digits (low order) are used for a serial number

  11. Multicast Octet Order Bit Order 7 - 0 7 - 0 7 - 0 7 - 0 7 - 0 7 - 0 Manufacturer's Address Serial Number Multicast Bit

  12. Fast Ethernet Transmission Medium

  13. Gigabit Ethernet • Latest extension to Ethernet • 1000 Mbit/s - 10 times faster than Fast Ethernet • Compatible with existing Ethernet

  14. Token Ring Network

  15. Advantages of Token Ring • High reliability, the ring can continue normal operation despite any single fault • Bypassing inactive stations • Effective use, 95% in Token Ring only whilst 30-40% in Ethernet • Excellent traffic handling • Large maximum frame length • High bandwidth efficiency. 70% in Token Ring, 30% in Ethernet • Many media choices: UTP, STP, coaxial or optical fibre • Supports transmission priority

  16. Frame Formats

  17. Token Ring Management • Sending out a new token if one is lost • Re-sending messages • Ensuring that the token is passed in its proper sequence • Managing congestion • Automatically correcting network errors

  18. Token Ring PC Token MSAU PC PC PC

  19. FDDI Rings Failed Station Outer ring used for data Inner ring unused except during failure Inner ring unused except during failure Workstation Workstation A B

  20. Station Types • Dual attached station (DAS), which is connected to both rings • Single attached station (SAS), which is attached only to the primary ring • Dual attached concentrator (DAC), which is connected to both rings and provides connection for additional stations and concentrators. It is actually the root of a tree • Single attached concentrator (SAC), which is connected only to the primary ring (through a tree)

  21. Main Steps in a Normal Frame Transmission 1. Sending station waits for token. 2. Sending station captures and strips token, and then transmits frames. 3. Sending station issues token at the end of transmission. 4. Destination station copies the transmitted frame and sets the A and C bits (address recognised and frame copied indicators). 5. Sending station removes the data from the ring by stripping the sent (and acknowledged) frame. 6. The first bytes of the frame are not stripped, and continue to circulate on the ring (as a fragment). Each repeating station strips one byte from the fragment, and a transmitting station completely strips it

  22. Frame Formats

  23. Wireless LAN

  24. Peer-to-Peer

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