CIS 3210 Lecture Notes - Lecture 37: Ethernet Frame, Mac Address, Collision Detection

• School: University of Guelph
• Department: Computing and Information Science
• Course: CIS 3210
• Professor: Xiaodong Lin

Document Summary

Sending adapter encapsulates ip datagram in ethernet frame. Preamble: 7 bytes with the speci c pattern used to synchronize the receiver, sender clock rates. No handshaking between sending and receiving nics. Receiving nic doesn"t send acks or naks to sending nic. Examine incoming frame"s mac address, selectively forward from to one-or-more outgoing links when frame is to be forwarded on segment, uses csma/cd. (csma - carrier sense multiple access / collision detection) Hosts are unaware of presence of switches. Switches do not need to be con gured. Hosts have dedicated, direct connection to switch. Ethernet protocol used on each incoming link, but no collisions; full duplex. Each link is its own collision domain. Switching: a-to-a can transmit simultaneously. Each switch has a switch table, each entry has: Mac address of host, interface to reach host, time stamp. Switch learns which hosts can be reached though which interfaces. When frame received switch learns location of sender: incoming lan segment.