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RE: [10GBASE-T] Technical feasibility: AutoNegotiation


I'd like to offer my opinion on this - as someone who has had to deal
with many AN related link issues.

> Perhaps someone can give me a quick pointer on how we are going to
> the issue of <100m cable plants that meet ISO 11801 specs not being
> to
> support 10GBASE-T.
> For example, I have a building full of CAT5e and CAT6 cables. The
> were installed to specification. Now, all I see are patch panels and
> jacks. I don't have a record of which cable is how long, or what its
> electrical specs are.

This is probably a common scenario.  We're in the process of rewiring
the LBNL Berkeley site and part of the project is to keep a database of
all test results for the installed cables.  I would hope this is the
case in general since most test equipment makes this relatively easy to

> The current Auto-Negotiation protocol supports HCD resolution which
> that the link, if configured to 10GBASE-T, will resolve to that speed
> both ends of the link support it. However, if the cable (85m of CAT6)
> not, the link will bounce up and down as it negotiates to speed, then
> fails
> to link. Maybe even worse is the link that actually comes up, but
> unreliably due to thermal variation causing changes in parametric
> and
> suffers excessive BER or drops link occasionally.
> What is the fix?

I would MUCH rather see the link fail to come up than to have it come up
and operate unreliably.

> Do I test the wire in advance of using 10GBASE-T?

Do you mean as a matter of installation practice or as a part of the
Auto-Negotiation process?

> Do we fix the Auto-Negotiation protocol to automatically drop speed if
> SNR gets too low to guarantee the BER?

Again, I would rather that it drop the link.  Since AN only runs when
you try to establish the link, are you talking about continuous BER

> If these have already been addressed, please feel free to just send
> to the presentation.

I think these are good questions - and I would like to hear more about
how the speed would be negotiated for the multi-speed PHY as I never
heard any formal discussion on this.  If there's a presentation on that,
I'd like the URL as well.