"Bob Shuman" wrote in message
...
Simple question on your excellent response which answers the 2 pair vs. 4
pair question:

100BaseT is 100Mbps full duplex. This means it can pass 100Mbps in both
directions simultaneously. This is done by using a pair of wires in each
direction (uplink=send/downlink=receive). You indicate that GbE is a full
1000Mbps and uses the 4 pairs which each send 250Mbps. Does this imply
that
GbE is now half duplex or that the send uses 2 pairs and the receive
another
pair? What is the maximum SIMULTANEOUS transmission rates in the uplink
and
downlink? Can you provide some insight since I had always assumed GbE was
also 1000Mbps full duplex like 100BaseT Fast Ethernet.

Thanks in advance for your insight here. It is important to understand if
GbE is 5 times or 10 times faster than FE.

Bob


Bob -

Excellent question, and I am laughing .. because I was never in favor of
using with copper cabling with GbE (I preferred the usage of fiber optic
cabling).

I have not participated or even kept up with GbE and the current 10 GbE
discussions (and roadblocks) for several years.

1000BASE-T is one (1) of the fours (4) physical layers or transceivers
defined by the two GbE (Gigabit Ethernet) standards:
IEEE 802.3z or 1000BASE-X and IEEE 802.3ab or 1000BASE-T.

1000BASE-X supports:
Multimode fiber media
Single-mode fiber media and
A short-reach, 25-meter Copper media jumper.

Because most of the cabling installed inside buildings today is Category 5
copper, the IEEE 802.3 1000BASE-T standard supports GbE operation over the
Category 5 cabling systems installed according to the specifications of
ANSI/TIA/EIA-568A (1992, revision A in 1995).

I will let you read the Cisco web page, Figure 7 answers your question
http://www.cisco.com/en/US/tech/tk38...080091a86.html