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Re: XAUI and 64b/66b


What several people is saying that making the 8B10B codes a required
precursor to the 64B/66B encoding removes the "optional" label that has been
put on XAUI.  You can have your cake and eat it too.  Either XAUI is an
optional XGMII extender and 8B10B is not part of the 64B/66B encoding, or
8B10B is part of 64B/66B and XAUI is a requirement for all implementations.

While I laud your work and experience with 8B10B, there are other solutions
that are just as elegant.  I recognize that you have wanted 8B10B to be part
of the requirements for 10GbE from day one.  This has perhaps clouded your
ability to be pragmatic.

If I were not pragmatic about the uses of protocols, I would be proposing
that we use HDLC, but I am not.  SDLC and HDLC have been around longer than
8B10B as communications protocols.  I have been working with SDLC and HDLC
as long if not longer than you have with 8B10B.  The first protocol that I
used to any extent other than SDLC was BiSync (1968).  Do you see me
suggesting these?  I am pragmatic and unlike the IETF, recognize that HDLC
has some major flaws and should not be part of  the requirements for 10GbE.

Again, is XAUI going to be optional or not?  If it is not optional, then I
think that you are going to have a hard time getting 75% of the people to
include it in the standard.  If XAUI is optional, then 8B10B encoding can
not be a required precursor to any PCS.  Which is it?

With respects,
Thank you,
Roy Bynum

----- Original Message -----
From: Rich Taborek <rtaborek@xxxxxxxxxxx>
To: HSSG <stds-802-3-hssg@xxxxxxxx>
Sent: Thursday, March 16, 2000 4:22 PM
Subject: Re: XAUI and 64b/66b

> Ben,
> I disagree with your direction on this issue for the same reason that I
> trouble with the lack of specification of an optional interface in
> which is implemented in 100% of Ethernet products implementing 1000BASE-X.
I may
> be being politically incorrect in stating this, but I typically like
products to
> match specs.
> I view XAUI as being a very prevalent 10 GbE interface, perhaps not as
> as the serial side of the GbE Ten-Bit-Interface. Barring no other complete
> workable XAUI/XGXS proposals that meet the requirements of an optional
> extender, my view is that the PCS should accommodate the optional XGMII
> as well as operate properly without one. Since we'll have multiple PCS's
> probably corresponding to PMA/PMDs, and one of the heavily backed (27
> Serial PHY proposals endorse a 64B/66B PCS, I believe that this PCS should
> support the optional XGMII extender which is specified to be PHY/PMD
> independent. The Serial PHY proposal already does this and I see no
benefit or
> savings in cost, complexity, etc. in removing it.
> I also see no significant difference in complexity between converting
> XGMII and PCS 64B/66B codes whether or not the IPG includes only /I/ or
> Best Regards,
> Rich
> --
> "Benjamin J. Brown" wrote:
> >
> > 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
> >
> > --
> > -----------------------------------------
> > Benjamin Brown
> > Router Products Division
> > Nortel Networks
> > 1 Bedford Farms,
> > Kilton Road
> > Bedford, NH 03110
> > 603-629-3027 - Work
> > 603-629-3070 - Fax
> > 603-798-4115 - Home
> > bebrown@xxxxxxxxxxxxxxxxxx
> > -----------------------------------------
> -------------------------------------------------------
> Richard Taborek Sr.                 Phone: 408-845-6102
> Chief Technology Officer             Cell: 408-832-3957
> nSerial Corporation                   Fax: 408-845-6114
> 2500-5 Augustine Dr.        mailto:rtaborek@xxxxxxxxxxx
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