Two Most Popular LANs
Ethernet (IEEE 802.3)
- bus topology (computers receive all messages, process only those addressed to them)
- logically and truly: bus (one central cable)
- physically (with a repeater): appears to be a star
- contention based MAC: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) = wait until the bus is free then transmit (analogies: “ordered chaos” or “small talk in a small group”)
Token Ring (IEEE 802.5)
- ring topology (computers receive all messages, process only those addressed to them)
- logically and truly: a ring
- physically (with a hub): appears to be a star
- MAC: Token Passing = wait for a free token, change it into a busy token, attach a message to it, retransmit it to the next computer in the circuit.
- (analogies: “free tokens,” “lost tokens,” and “token monitors”)