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RE: XAUI and 64b/66b

I don't know about Rich, but I definitely agree with you. The interface on
each side of XAUI should be XGMII. If the implementer chooses a different
i/f that is his choice.


> -----Original Message-----
> From: Benjamin J. Brown [mailto:bebrown@xxxxxxxxxxxxxxxxxx]
> Sent: Thursday, March 16, 2000 1:08 PM
> To: 802.3ae; Rich Taborek
> Subject: XAUI and 64b/66b
> Rich,
> Jonathan just sent me a note saying that I was even confusing
> him right now so I want to stop and ask my question again. I'll
> try to make this as clear as possible.
> In the layer diagram that Brad showed in Albuquerque, the XAUI
> was shown as an XGMII extender. To me this means that the
> reconcilation sub-layer speaks using XGMII language and the PCS
> listens using XGMII language. The XAUI can extend this interface
> by translating from XGMII to XAUI but it must translate back
> again before it gets to the PCS. The XGXS block is the translator.
> The 64b/66b proposal as written ignores the XGXS block between
> XAUI and the PCS. It is my contention that, though this would
> work, it is unnecessary and even burdensome to those implementors
> that choose to not use XAUI. 64b/66b would work equally as well
> without the XAUI specific control codes as they add nothing to
> the efficiencies of 64b/66b (that I can tell). The XGMII specific
> control codes are completely adequate for 64b/66b. In my opinion,
> a serial PCS should be specified as if XAUI didn't exist.
> I'll even go so far as to state that, in my opinion, even a
> parallel/CWDM PCS should be specified as if XAUI didn't exist.
> If this PCS turns out to be identical to the XGXS block then some
> implementors may choose to avoid the encode/decode/encode as
> specified in the standard, but I believe that is how it should
> be specified.
> Is the question/comment still confusing or do you merely disagree?
> Ben
> -- 
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> Benjamin Brown
> Router Products Division
> Nortel Networks
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