18-07-2012, 03:27 PM
Fast Ethernet and Gigabit Ethernet
Fast_Ethernet.pptx (Size: 955.75 KB / Downloads: 172)
Fast Ethernet Details
UTP Cable has a 30 MHz limit
Not feasible to use clock encoding (i.e., NO Manchester encoding)
Instead use bit encoding schemes with sufficient transitions for receiver to maintain clock synchronization.
100 Base TX
Uses two pair of twisted pair, one pair for transmission and one pair for reception.
Uses either STP or Cat 5 UTP.
Uses MTL-3 signaling scheme that involves three voltages.
Uses 4B/5B encoding.
There is a guaranteed signal transition at least every two bits.
Fast Ethernet Repeatersand Switches
Class I Repeater – supports unlike physical media segments (only one per collision domain)
Class II Repeater – limited to single physical media type (there may be two repeaters per collision domain)
Switches – to improve performance can add full-duplex and have autonegotiation for speed mismatches.
Gigabit Ethernet
Viewed as LAN solution while ATM is WAN solution.
Gigabit Ethernet can be shared (hub) or switched.
Shared Hub
Half duplex: CSMA/CD with MAC changes:
Carrier Extension
Frame Bursting
Switch
Full duplex: Buffered repeater called {Buffered Distributor}
Buffered Distributor
A buffered distributor is a new type of 802.3 hub where incoming frames are buffered in FIFO queues.
Each port has an input FIFO queue and an output FIFO queue.
A frame arriving at an input queue is forwarded to all output queues, except the one on the incoming port.
CSMA/CD arbitration is done inside the distributor to forward the frames to the output FIFOs.