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 Token passing for Token Ring and Token Bus LAN  flow and error control

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

Frame Format MAC frame format

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

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

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 = (2x10 8 m/s) x (51.2 us) / 2 = 5120m Time for sending the jamming signal and others (e.g., repeater) reduces it to 2500m

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

Cables for Ethernet Implementations

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

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

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

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

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

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

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

Topologies – Point-to-point, star, two stars, and hierarchy of stars Implementation

Homework Exercise in Chapter 13 – 16 – 17 – 18 – 19