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IST 201

IST 201. Chapter 7. Legacy Ethernet. 10Base5 10Base2 10BaseT Common Characteristics Timing parameters Frame format Transmission process Basic design rule. Parameters. Bit time 100 nanoseconds Slot time 512 bit-times Interframe spacing 96 bits Collision attempt limit 16

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IST 201

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  1. IST 201 Chapter 7

  2. Legacy Ethernet • 10Base5 • 10Base2 • 10BaseT • Common Characteristics • Timing parameters • Frame format • Transmission process • Basic design rule

  3. Parameters • Bit time 100 nanoseconds • Slot time 512 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

  4. Ethernet Frame • Must be between 64 – 1518 bytes #Octets 7 1 6 6 2 46-1500 4 S F D Length Type Preamble Destination Source Data FCS

  5. Encoding • Describes how bits are represented by voltages.

  6. Manchester Encoding • Used in 10 Mbps Ethernet • Direction of the edge transition indicates whether it is a one or zero. • Low to High transition 01 represents 1 • High to Low transition 10 represents 0 • Self-clocking – each bit is transmitted over a predetermined time period Called Biphase code

  7. Shared Ethernet • Share collision domain • Multiple types of media can co-exist • 10BaseT • 10Base2 • 10Base5

  8. Design Rule = 5-4-3 Rule • No more than 5 segments • Separated by no more than 4 repeaters • Coax – no more than 3 segments can have hosts • This rule prevents a 10 Mbps network from having propagation delay problems.

  9. 100 Mbps Ethernet (Fast Ethernet) • 100BaseTx – copper • 100BaseFx – fiber-multimode • Common characteristics • Timing parameters • Frame format • Parts of the transmission process

  10. Timing Parameters 100 Mbps • Bit time 10 nanoseconds • Slot time 512 bit-times • Interframe spacing 96 bits • Collision attempt limit 16 • Collision back-off limit 10 • Collision jam size 32 bits • Max. untagged frame size 1518 octets • Min. frame size 512 bits/64 octets

  11. 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.

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

  13. 1000 Mbps Ethernet • 1000BaseT – Twisted pair • 1000Base-SX - short wave laser or LED on multimode • 1000BaseLX – long wave laser on single mode or multimode (recommended for Backbones)

  14. 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

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

  16. 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.

  17. 1000BaseSX & LX • Fiber • Most often 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”

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