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Physical & Data-link

Physical & Data-link. ISQS 6343 #2 John R. Durrett. Media Access Methods. Most important choice is MAC Drives: cable installed performance, cost, reliability IEEE 802 series standards Frame layout: Mac head | LLC head | IP | TCP | data | CRC ARCnet (obsolete). Token Ring. Pros:

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Physical & Data-link

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  1. Physical & Data-link ISQS 6343 #2 John R. Durrett

  2. Media Access Methods • Most important choice is MAC • Drives: • cable installed • performance, cost, reliability • IEEE 802 series standards • Frame layout: • Mac head | LLC head | IP | TCP | data | CRC • ARCnet (obsolete)

  3. Token Ring • Pros: • fast, reliable • well supported by IBM • Cons: • expensive, not widely accepted • Details: • token-based • physical: star or bus, logical: bus • IEEE 802.5 • STP, Coax, Optic fiber, UTP

  4. Ethernet • Bob Metcalfe • CSMA/CD • Carrier Sense - used/idle • Multiple Access - equal right to access • baseband - one transmission at a time • Collision Detection • Physical: star, Logical: bus

  5. High-Speed Ethernet • Full Duplex • new hubs, etc. • 100BaseT • UTP, STP, Fiber • Round Trip delay == limits cable length • 100VG • demand priority • four pairs Cat 3

  6. High-Speed Ethernet

  7. Other High-Speed MAC • FDDI • Fiber • Backbone • CDDI • ATM

  8. Network Cabling • Circulatory system of network • Documentation (BA slides) • Installation very labor intensive • ANSI/TIA/EIA 568 & 569 • generic voice & data standards • multi-vendor • performance & technical criteria • Media, Topology, Distances, Interfaces, Hardware, Performance

  9. Topologies • Physical - way components are connected • Electrical - how functions as a circuit • Logical - way system functions as a whole • Bus • ends terminated • simple to run, hard to fix • Star • hub=based, main choice • Ring • like bus but no termination

  10. Cabling • Coaxial • Thick net (Ethernet 10B5) • Thin net (Ethernet 10B2) • STP • UTP (dominates LANs) • 10BT, IEEE 802.3 • 4 pair up / cable • Cat 3, 4, 5 • distance & signaling rate • 100m total/client • Electrical interference • Fiber

  11. Network Interface Cards • Maintain consistency • in every network device • physical: electrical connection • data-link: assembles frames • media dependent • MAC dependent • Protocol independent • Bus type, configuration, remote boot, client Vs. server

  12. Repeaters • Clean-up, amplify, rebroadcast • physical layer • media dependent • protocol independent • all other active network components contain repeater functionality

  13. Hubs • Concentrators • Multi-port repeaters • Standalone Vs. stackable • Manageability

  14. Bridge • Data-link layer • frame-based • media dependent • higher protocol independent • physical address of source & destination part of frame header • Listens for “outbound” address

  15. Router • Media independent • higher protocol independent • packet headers used for logical addresses • More complex decisions than hubs • Network layer • routable upper-level protocol

  16. Gateways • Translation at 1 or more layers • Most common at upper three layers • Ex: SMTP to MHS

  17. Switch • Broadcast Vs. virtual circuit • Store-and-forward • error checking • filtering • security • cut-through • speed • Virtual LANs

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