RE: [EFM] 100 Mbps Proposals
Behrooz
At 01:39 PM 2/14/02 -0800, Behrooz Rezvani wrote:
Sorry just got of a meeting did not realize
that I have created some
confusion:
You are right Geoff. 100BASE-T4 was 100 Meg combined on a single pair.
No, it was 100 Mb/s on 3 pair. There was one pair dedicated to each
direction and 2 pair that were used in the direction of data
transmission. It only takes one pair to easily handle the carrier sense
information. So the CSMA/CD was done on 1 pair each direction. The data
transmission was done on 3 pairs with 8B/6T encoding. See Figs 23-3,
23-4, 23-23. That is why you can't do full duplex on 100BASE-T4.
So this is not that. I am suggesting just like
100BASE-T put 25Meg full duplex on each pair
100BASE-T does not put 25Meg full duplex on each pair.
I assume that you mean that 1000BASE-T puts 25Meg full duplex on each
pair. That is not true either. There is no pair specific coding in
1000BASE-T. The coding is spread over all 4 pair at once. The decoder
looks at 5 levels on 4 pairs (which yields a code space of 625 points)
and derives 1 byte from it (256 code points plus control codes). The
excess code space is used to provide more than one possible code target
for the subsequent code. Choosing the one that provides the greatest
voltage swing generates extra noise immunity.
And,
Barry
you are correct Spectrum compatibility should be dealt with I think it
can
be dealt with on 400-500 meter reaches
If the team thinks that there is interest for 100 Meg I'll be happy to
send
a short presentation off line to people who are interested
Thanks
Behrooz
-----Original Message-----
From: Geoff Thompson
[mailto:gthompso@xxxxxxxxxxxxxxxxxx]
Sent: Thursday, February 14, 2002 1:09 PM
To: O'Mahony, Barry
Cc: 'larry rennie'; Behrooz Rezvani; Bruce Tolley;
stds-802-3-efm@ieee.org; Roy Bynum
Subject: RE: [EFM] 100 Mbps Proposals
In addition, 100BASE-T4 does not support full duplex
Geoff
At 12:04 PM 2/14/02 -0800, O'Mahony, Barry wrote:
>As was brought up in Raleigh, it has not been demonstrated that
100BASE-T4
>meets the spectrum compatibility objective (and it is unlikely that
it
>does). Leaving aside the discussion as to how close installed
POTS wiring
>is to CAT3.
>
>There may be MxU instances where spectrum compatibility is not
required,
and
>instances where it would be. It is an adopted EFM objective,
however.
>
>~~~~~~~~~~~~~~~~~~~~~~~
>Barry O'Mahony
>Intel Labs
>Hillsboro, OR, USA
>tel: +1 (503) 264-8579
>barry.omahony@xxxxxxxxx
>barry.omahony@xxxxxxxxxxxx
>~~~~~~~~~~~~~~~~~~~~~~~
>
>
>-----Original Message-----
>From: larry rennie
[mailto:Larry.Rennie@xxxxxxx]
>Sent: Thursday, February 14, 2002 11:28 AM
>To: Behrooz Rezvani
>Cc: Bruce Tolley; stds-802-3-efm@ieee.org; Roy Bynum
>Subject: Re: [EFM] 100 Mbps Proposals
>
>
>
>Behrooz,
>
>Is not 100BASE-T4 100Mbits/sec over 4, Cu pairs?
>
>Larry
>
>Behrooz Rezvani wrote:
>
> > Bruce,
> >
> > if there is a success in starting such an effort, I would very
much to
> > encourage you and other people to consider 100 mbps over 4
copper pairs
>for
> > reach <xyz> meters. That has a lot more practical
applications in MxU.
> >
> > Thanks
> > Behrooz
> > ----- Original Message -----
> > From: "Roy Bynum"
<rabynum@xxxxxxxxxxxxxx>
> > To: "Bruce Tolley" <btolley@xxxxxxxxx>;
<stds-802-3-efm@ieee.org>
> > Sent: Wednesday, February 13, 2002 7:59 PM
> > Subject: Re: [EFM] 100 Mbps Proposals
> >
> > >
> > > Bruce,
> > >
> > > I am concerned about putting effort into developing a
standard for
> > > technology that already exists for a market that is
current, not
greatly
> > in
> > > the future.
> > >
> > > Thank you,
> > > Roy Bynum
> > >
> > > At 07:48 PM 2/13/2002 -0800, Bruce Tolley wrote:
> > >
> > > >Colleagues:
> > > >
> > > >Those of you who are also on the 802.3 reflector saw
that there is
call
> > > >for interest on the agenda of the March meeting in St
Louis to
discuss
> > > >starting a 100 Mbps dual fiber SM fiber project
outside of 802.3ah
task
> > force.
> > > >
> > > >While I have not yet decided where I stand on 100 Mbps
solutions for
>EFM,
> > > >I wanted to communicate that I think this call for
interest is
>premature,
> > > >I would strongly encourage the proponents of 100 Mbps
on SM fiber to
> > > >converge on one strong proposal for the March IEEE
802.3ah meeting.
> > > >
> > > >We are already facing the challenge of perhaps too
many EFM PHYs. To
> > > >specify an additional PHY for EFM outside of the
802.3ah TF only
makes
> > > >life more difficult.
> > > >
> > > >Bruce
> > >