Re: XAUI and 64b/66b
Rick,
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).
Ben
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
--
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Benjamin Brown
Router Products Division
Nortel Networks
1 Bedford Farms,
Kilton Road
Bedford, NH 03110
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