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Velu, I think Brad was suggesting earlier using
Clause 73 for backplane/copper auto-negotiation and possibly using Clause 37
for next gen optics speed negotiation. I take your point that you are talking
about making adjustments after an operating speed has been selected however it
may be necessary to do AN to select the operating speed in the first place. I
don’t see the problem with using 8b10b coding for next gen optics speed
AN. The problem with Clause 37 is that it assumes a single physical lane and
that the baud rate may be inappropriate for the components making up the link. These
problems may turn out to have easy solutions. On reflection my comment below
ruling out Clause 73 AN for next gen optics might have been premature. It might
be possible to transport the Clause 73 protocol over optics. Arthur. From: Velu Pillai [mailto:vpillai@xxxxxxxxxxxx] Yes, What I meant by a new clause is
to come up with the protocol to support at speed exchange, rather than opening up Clause 37 and
modifying it. Regards, Velu Pillai From: Brad Booth [mailto:Brad_Booth@xxxxxxxx] Velu, That’s the concept
behind using sequence ordered sets. The protocol is already specified and would
only need minimal modifications to support “at speed” exchanges. Cheers, From: Velu Pillai [mailto:vpillai@xxxxxxxxxxxx] Hi Arthur, CL37 is a 8b10b code-word based page
exchange, hence using it for next generation optical PHYs is not possible. We can come up with a new clause to do
“at speed” auto-negotiation. In back-plane it will be used after
the training sequence to exchange abilities and request for next generation
PHYs. Clause 73 will classify the PHY and this new clause will handle the
advanced abilities. And in Optical PHYs, this will act as the primary
auto-negotiation. This way a common negotiation Clause can exist between the
Back-plane/twinax and Optical PHYs. Regards, Velu Pillai From: Arthur Marris [mailto:arthurm@xxxxxxxxxxx] Brad, Let me make a
few comments. For 802.3bj it
is necessary to use Clause 73 for auto-negotiation because Clause 73 already
supports port types for four-lane twinax and back-plane. If new 100G port types
are being added for these media, they need to be included in Clause 73. Clause
73 also gives you FEC negotiation for free. Clause 73
clearly does not work over optical media. You can use
ordered sets for exchanging ability and requests, but this only works if both
sides of the link are running at the same speed and the error ratio is not too
bad. For next generation optics you are going to need to decide whether you
need to negotiate speed in addition to determining FEC operation (for example
you might want to negotiate between 40GBASE-SR4 and 100GBASE-SR4). If you do
decide to negotiate speed you could consider re-using Clause 37 for
auto-negotiation (which operates at a 1.25G data-rate). If you are not
negotiating speed but are just concerned about bit errors, then the task being
performed is really link training rather than ability resolution. Arthur. From: Brad Booth [mailto:Brad_Booth@xxxxxxxx] Stephen, It depends on the FEC
protocol adopted, implementation requirement, and the associated latency. The
discussion got started around the idea of using Clause 73 AN for FEC ability
exchange in the optical domain. Considering we’re still
in the study group phase, some of those questions cannot be answered as we have
not adopted an FEC proposal. If an exchange protocol is required, then IMHO the
use of sequence ordered sets would be preferred over creating of a new autoneg
protocol. Cheers, |