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


"gb" wrote in message
. ..

INCORRECT, when the 100 Mb standard was being developed there were other
proposals that did call for all four (4) pairs to be used.
One argument 10 years ago -- that many installations (wiring closet to PC
desktop) were not compliant with EIA/TIA 568 (1992)-- and added undue cost
in rewiring these installations.

The referenced Cisco web page references the IEEE standards on which these
network solutions operate.

As Figure 7 shows, 1000BASE-T (1 Gb) works by using all four of the
Category
5 pairs to achieve 1000 Mbps operation over the installed Category 5
copper
cabling. 1000 Mbps data rates are achieved by sending and receiving a 250
Mbps data stream over each of the four (4) pairs simultaneously (4 X 250
Mbps = 1 Gbps).

In contrast, 100BASE-TX uses two (2) pairs: one to transmit and one to
receive. Fast Ethernet on Copper (100BASE-TX) achieves 100 Mbps operation
by
sending encoded symbols across the link at a symbol rate of 125 Mbaud.

gb
IEEE member
Standards
Communications