Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: XAUI and 64b/66b


This is what I was asking for when I started this thread.
Your presentation had only XAUI encodings transported over
the 64b/66b. I asked for only XGMII (encodings, not the actual
physical interface). Since you didn't weigh in, I assumed your
position hadn't changed. I was compromising with Rich Taborek,
thinking I'd really accomplished something.

I agree with you whole-heartedly on all of your comments. Can
we sway Rich on this? I know we've heard from several others
earlier in this thread but I can't recall who they were at this
point (sorry for my poor memory).


Rick Walker wrote:
> Dear Ben,
> > "Brown, Ben [BAY:NHBED:DS48]" <bebrown@xxxxxxxxxxxxxxxxxx> writes:
> > I need to apologize to you. I've been having this conversation
> > with Rich Taborek as if it is his proposal and not including
> > you. Please, accept my apology and chime in any time with your
> > opinion.
> No problem.  It's the information flow that counts.  Thanks for
> thinking of me, though.
> > Wonderful! I agree with you completely. This means the transmit
> > PCS simply 64b/66b encodes the information it gets from the MAC
> > service interface, be this information in the form of XGMII
> > encodings or XAUI encodings.
> I don't like this.
> I think that a reasonable alternative would be for XAUI to always
> take in XGMII and deliver XGMII.  A 64b/66b code has no business
> indicating /A/ characters.  None at all.
> All PMD's could take their input from pure XGMII and convert back to
> XGMII at their output.  It makes no sense to burden all the PMDs with
> complex rules for converting between the idiosyncrasies of other coding
> schemes.
> > The receive PCS must have the intelligence to know whether its MAC
> > service interface requires XAUI encodings or XGMII encodings.
> This is really bad.  If a future new PMD is invented, how do you upgrade
> all the installed base of PMDs to have the new "intelligence" to know
> about how this new PMD operates?
> > It simply 66b/64b decodes the information then may pass the data
> > straight through or convert it to XAUI or XGMII, whichever is
> > applicable.
> I think that all PMDs should operate on and deliver pure XGMII signals.
> > Rich Taborek writes:
> > The only thing I disagree with is a REQUIREMENT to implement the XGMII
> > between the PCS and XGXS.  The writing of the standard should not
> > basterdize straightforward implementations.
> Of course, I don't mean here that you actually need a 36-bit bus in your
> physical implementation, just that the space of control signals should
> be strictly limited to the fully sufficient set defined for XGMII.  This
> does not bastardize the implementation - it is simply a guideline for
> what sorts of signalling is supported by a PMD.
> Best regards,
> --
> Rick Walker

Benjamin Brown
Router Products Division
Nortel Networks
1 Bedford Farms,
Kilton Road
Bedford, NH 03110
603-629-3027 - Work
603-624-4382 - Fax
603-798-4115 - Home