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IST 201

IST 201. Chapter 7. Repeater Classes. Class I Between one Ethernet media and another of the same speed Any unlabeled repeater Class II Daisy-chaining is ok if cable length is less than 5 meters. Repeaters cannot adapt between speeds. Bridges connect Ethernet segments of differing speeds.

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IST 201

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  1. IST 201 Chapter 7

  2. Repeater Classes • Class I • Between one Ethernet media and another of the same speed • Any unlabeled repeater • Class II • Daisy-chaining is ok if cable length is less than 5 meters. • Repeaters cannot adapt between speeds. • Bridges connect Ethernet segments of differing speeds.

  3. Link Configuration • Autonegotiate – preferable • Manual configuration is ok if autonegotiate fails.

  4. 1000 Mbps Ethernet • 1000BaseT – Twisted pair • 1000Base-SX - short wave laser or LED on multimode • 1000BaseLX – long wave laser on single mode or multimode

  5. 1000-Mbps Parameters • Bit time 1 nanoseconds • Slot time 4096 bit-times • Interframe spacing 96 bits • Collision attempt limit 16 • Collision back-off limit 10 • Collision jam size 32 bits • Max. frame size 1518 octets • Min. frame size 512 bits/64 octets

  6. Frame • Same for all Ethernet.

  7. Transmission • Bits are sent faster • Shorter duration • Require more timing considerations • Pushing bandwidth limits • More susceptible to noise

  8. Encoding • Symbols used for data and controls • Improves transmission of efficiency • Improves synchronization • Improves bandwidth efficiency • Improves SNR characteristics

  9. 1000BaseT Encoding • 8B1Q4

  10. Line Encoding • 4D-PAM5 • Cat5e or better • Uses all 4 wire pairs in full duplex simultaneously • Operates in permanent collision • Send/receive on same pair • Uses sophisticated hybrid circuits • Uses a technique called echo cancellation • Varied voltage levels • Level 1 forward error correction (FEC) • Careful cabling to standard prevents problems with • Noise

  11. Interoperability • Gigabit Ethernet • Fast Ethernet • 10BaseT • Bridge provides transfer from one speed to another • Important for office desktop applications • Wiring closets

  12. Half Duplex – 1000BaseT • Works with CSMA/CD in half-duplex • Not recommended

  13. Timing • Master clocking Mark time for • Slave clocking transmissions • Autonegotiate or manual configured for which device will act in which role. • Usually a multiport device handles the master role when autonegotiate determines.

  14. 1000BaseSX & LX • Fiber • Most recommended for backbones • Group FastEthernet devices • Good noise immunity • No ground problems between floors/buildings • New device options • Excellent distance characteristics • Not susceptible to dc drift (bias) that causes clocking errors (same digit represented sequentially) • Not usually used for office desktop connections • Copper 10/100/1000 network interfaces are common • Copper is more “user proof”

  15. Encoding • 8B/10B

  16. Line Encoding • NRZ – level driven not edge driven

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