RE: [10GBASE-T] Reflections
We did not use or even consider the Shannon capacity of twisted pair
cabling in our previous work.
We did do a lot of investigation into twisted pair cabling
characteristics when we developed 1BASE5 and 10BASE-T. After that
experience we decided that we didn't want to do cabling and worked very
that useful specs for our applications were developed in TIA and SC
When those cabling groups were starting on their specification of Cat 6
we did ask them to characterize the cabling well beyond the zero ACR
point (their traditional cutoff point). They, in fact, did so. What all
of this discussion is about is that they didn't go out far enough so
support this project.
At 10:17 AM 3/3/2003 -0800, Sreen Raghavan wrote:
there may have been innovations in DSP architectures since 1997, Shannon
Capacity of CAT5/6 cables is a theoretical limit, and is unaffected by an
individual s time horizon, or implementation sophistication.
Vativ Technologies, Inc.
On Behalf Of GEisler@aol.com
Sent: Friday, February 28, 2003 8:44 AM
Subject: [10GBASE-T] Reflections
Nice to hear from a lot of the old crew that created the 1000BASE-T
standard. I think that you can all take a bow, judging from what is
happening in the market and the remarkable improvements in
implementations achieved in three short years. But no good deed goes
unpunished, as they say, so you guys earned the job (and created the need
for) taking the next step up. Without a doubt, there are big jumps in the
performance demanded and we don't have the luxury that 1000BASE-T
enjoyed, namely the introduction of coding into the design. That has been
done already. This time around, we have to take advantage of the residual
capacity of the cabling, which we barely touched.
On the other hand, you will agree that the levels of sophistication in
analysis and implementation of DSP based systems has also increased
dramatically since 1997, when GigT started in earnest.
While I enjoyed fond memories of your recollections of what we knew (or
suspected) then and what we added later when we got smarter, it strikes
me that that history is relatively immaterial today. That was then and
our current circumstances are quite different. We now need to agree in
the study group that it is feasible to do 10Gig on some form of
twisted pair cabling at the desired length and go on to form a Task Force
to do the hard work of coming to agreement on the precise details of the
signaling and channel specifications.
It is clear that the channel specifications as written in 11801 will have
to be modified and expanded for our use and installation qualification
test parameters will have to be defined. This is more or less what
happened for 1000BASE-T and seems to me to be a normal and reasonable
step. After all, why should the cabling industry be expected to have
already characterized cabling for the use of a standard for which we are
still in the Study Group phase? As for installed cabling, we will see
whether or how it may be qualified for 10G as part of our effort.
I look forward to our meeting in Dallas and hope that we can get to work
on a PAR draft there.