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Ch 13. Wired LANs: Ethernet

Ch 13. Wired LANs: Ethernet. 13.1 IEEE Standards. Project 802 launched in 1985 To set standards to enable intercommunication among equipment from a variety of manufacturers. Data Link Layers. Framing Logical Link Control (LLC) Medium Access Control (MAC) CSMA/CD for Ethernet LAN

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Ch 13. Wired LANs: Ethernet

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  1. Ch 13. Wired LANs: Ethernet

  2. 13.1 IEEE Standards • Project 802 launched in 1985 • To set standards to enable intercommunication among equipment from a variety of manufacturers

  3. Data Link Layers • Framing • Logical Link Control (LLC) • Medium Access Control (MAC) • CSMA/CD for Ethernet LAN • Token passing for Token Ring and Token Bus LAN  flow and error control

  4. 13.2 Standard Ethernet • Ethernet • Originally developed at Xerox’s Palo Alto Research Center (1976) • Generations • Standard Ethernet: up to 10 Mbps • Fast Ethernet: up to 100 Mbps • Gigabit Ethernet: up to 1 Gbps • Ten Gigabit Ethernet: up to 10 Gbps

  5. Frame Format • 802.3 MAC frame format

  6. Frame Length • Minimum length is required for collision detection • Maximum length is for small buffer size and preventing monopoly of shared medium

  7. Physical Address • Addressing • 6-byte physical address, in hexadecimal notation • Usually dedicated to network interface card (NIC) • Support unicast, multicast, and broadcast • Refer to the textbook

  8. Multiple Access • Access method • 1-persistent CSMA/CD • Slot-time = round-trip time + time to send the jamming • Defined in bits: 512 bits (= 51.2 us over 10-Mbps Ethernet) • To detect collision on time, a station should be able to detect a collision before it sends out the minimum-size frame (512 bits) • Maximum network length • = propagation speed x slot time / 2 • = (2x108m/s) x (51.2 us) / 2 = 5120m • Time for sending the jamming signal and others (e.g., repeater) reduces it to 2500m

  9. Coding • Now, we move from MAC to PHY • Manchester encoding and decoding • Help synchronization owing to the transition in the middle • Requires doubled signal rate of the original

  10. Cables for Ethernet • Implementations

  11. 13.3 Changes in the Standard • Bridged Ethernet • Connect two or more Ethernet networks by “bridge” • Bridge acts as a station in each separate network, and prevents signals from propagating across networks • Effects of bridge • Raising the bandwidth • Separating collision domains domain domain

  12. Layer 2 switch or switching hub • Switched Ethernet • Multi-port bridge allows the bandwidth is shared only between the station and the switch

  13. Full-Duplex Ethernet • Increase the capacity of each domain from 10 Mbps up to 20 Mbps

  14. 13.4 Fast Ethernet • IEEE 802.3u • Upgrade the data rate to 100 Mbps • Make it compatible with Standard Ethernet • Keep the same 48-bit address • Keep the same frame format • Keep the same min. and max. frame lengths • MAC • CSMA/CD • Autonegotiation

  15. PHY • Point-to-point or start topologies only (no bus topo.) • Implementation

  16. 13.5 Gigabit Ethernet • IEEE 802.3z • Upgrade the data rate to 1 Gbps • Make it compatible with Standard or Fast Ethernet • Use the same 48-bit address • Use the same frame format • Keep the same min. and max. frame lengths • Support autoconfiguration as defined in Fast Ethernet

  17. Modes of Gigabit Ethernet • Full-duplex mode with switch – mostly used • Half-duplex mode with hub • Traditional: 512-bit min. frame  slot time = 0.512us  max. network length = 25m • Carrier extension: 512-byte min. frame slot time = 4.098us  max. network length = 200m • Frame bursting: combine multiple short frames as a single frame

  18. Topologies • Point-to-point, star, two stars, and hierarchy of stars • Implementation

  19. Homework • Exercise in Chapter 13 • 16 • 17 • 18 • 19

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