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Subnets

Subnets. Token Ring. Access Methodology = token passing Logical topology = sequential Physical = traditionally ring, currently star Logical ring, physical star. Token Ring. Token Ring Overview Token Ring Architecture was developed in the 1980s Ethernet is the most popular

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Subnets

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  1. Subnets

  2. Token Ring • Access Methodology = token passing • Logical topology = sequential • Physical = traditionally ring, currently star • Logical ring, physical star

  3. Token Ring • Token Ring Overview • Token Ring Architecture was developed in the 1980s • Ethernet is the most popular • IEEE 802.5 Standards • IBMs • PCs • Midrange Computers • Systems Network Architecture • 1985 – IBM became an ANSI standard

  4. Token Ring • Token Ring networks can run at 4, 16, or 100 Mbps • High-Speed Token Ring (HSTR) • Use token-passing routine and star-ring hybrid physical topology • Token passing: 3-byte packet (token) transmitted between nodes in circular fashion around ring • When station has something to send, picks up token, changes it to a frame, adds header, information and trailer fields • All nodes read frame as it traverses ring

  5. Token Ring • Token-passing control scheme avoids possibility for collisions • More reliable and efficient than Ethernet • Active monitor: maintains timing for ring passing, monitors token and frame transmission, detects lost tokens, corrects errors • Token Ring connections rely on NIC that taps into network through a MAU • Self-shorting feature of Token Ring MAU ports makes Token Ring highly fault tolerant

  6. Token Ring Data Frame

  7. Free Token.. Control of the Token.. Flagging a Token..

  8. Logical Ring

  9. Token Ring (continued) Interconnected Token Ring MAUs

  10. Monitoring the system • First PC to come online • Ensures the delivery of the token • Checks frames • Beaconing • Notification of lack of contact • Sends a message with source and the address of the PC that didn’t respond • Repairs • Active monitor • Recognising a computer • Checking for duplicate addresses • Notification

  11. Hardware Components • Hub houses the ring • Multiple Hubs • STP; UTP • Patch Cables • Fibre-Optic Cable • MAU • MSAU • SMAU

  12. Hub Capacity • IBM MSAU • 10 Connection ports • 8 Computers • Each ring can have up to 33 Hubs • MSAU: • 72 Computers; UTP • 260; STP • Each connected so part of the logical ring

  13. Adding Hubs

  14. Built-in Fault Tolerance • Token-passing • NIC Failure • Detects and disconnects from the failure point • No affect on the ring

  15. Hub to Computer Distance

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