At 11:56 AM 1/11/02, mlh wrote: >how many pairs of two-twisted cable are used for full-duplex Ethernet ? what >is the >difference between full- and half- duplex cable?
10Base-T and 100Base-T unshielded twisted-pair cabling uses two pairs, for both full duplex and half duplex. There's a transmit pair and a receive pair. A station's transmit pair gets crossed over at the hub or switch to mean receive at the hub or switch. The hub or switch's transmit pair becomes receive at the station. It's not the cabling that distinguishes half-duplex and full-duplex. It's the logical topology, hardware, and configuration. With half-duplex, if a station receives bits on its receive pair while transmitting bits on its transmit pair, this is considered a collision. The station must stop transmitting, back off, and retransmit. A half-duplex network is shared. Every device on the hub (or coax cable) shares the bandwidth and must obey the rules of Carrier Sense Multiple Access, Collision Detect. Listen before sending. Listen while sending to see if another station started sending at the same time and back off if that's the case. Full duplex works on a point-to-point link between a station and a switch. Bandwidth is not shared. In this case, receiving while you are sending it perfectly legitimate. So, to upgrade a network from half-duplex to full-duplex doesn't require new cabling, but it does require a new logical topology and possibly new hardware: switches and Network Interface Cards (NICs) that support full duplex. It also requires that the administrator configure everything for full duplex (or use auto-negotiation which is risky because it's buggy.) Hope that helps. Priscilla >Thank you in advance. > > > >Regrads, > >mlh ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=31655&t=31643 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
