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Ethernet Computer Networks Lecture 4 http://goo.gl/pZE5o8 The History of Ethernet Originally: DIX Ethernet (DEC-Intel-Xerox, Ethernet II) - 10Mbps. No LLC sublayer Later standardized as: IEEE 802.3 Frame format has changed: (type/length field interpretation). Both frame formats are being used today even on the same medium 2 Naming of Ethernet Family Members According to IEEE 802.3 Today, Ethernet is a whole technology suite with a common frame format (both LAN and WAN technologies) {Mbps|GbpsG}{Base|Broad}{seg_len/100[m]|-medium} Medium: T/TX – Twisted Pair, F/LX/SX/… – Fiber optic, … Examples: 10Base5, 10Base-T, 100Base-LX10, 10GBase-T 10Base5, 10Base-T, 100Base-LX10, 10GBase-T 3 Half-duplex Ethernet MAC Access Protocol: CSMA/CD p-persistant Maximum signal delay in the Ethernet network is defined to be 51,2 microseconds 2x maximum time of signal propagation + delays incured by repeaters/hubs Corresponds to 512 bit intervals (64B) at 10Mb/s Implies the maximum network reach and maximum number of repeaters/hubs with a standardized maximum signal delay (5-4-3 rule) A station that detects collision sends a jam signal which helps other stations to detect the collision to limit the duration of a collision 4 Exponential backoff is applied after a collision Half-duplex and Full-duplex Ethernet Half duplex – colission envirnment (CSMA/CD) In half-duplex mode we