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Re: I/F locations


I have to respectfully disagree that the XSBI is in any way a required
interface of the 10GBASE-LW4 PHY. As you clearly indicate in D2.0,
Clause 53, Figure 53-1, the XSBI is an optional interface for the
10GBASE-LW4 PHY. Figure 53-1 clearly illustrates that the WIS may be
directly attached to the LW4 PMA.

I don't understand your point of suggesting the extraneous insertion of
a high pin count, extraneous parallel interface (the XSBI) into the
10GBASE-LR4 PHY. Is there some specific benefit or purpose of this

I am very confused by your second paragraph where you mention as SUPI
"extension" to allow WWDM attachment to the LAN 64b/66b encoder over

1) All of the aforementioned elements, with the exception of the XSBI,
are required for the 10GBASE-LW4 PHY;

2) SUPI is a PMA which is only applicable to the 10GBASE-LW4 PHY. It is
not applicable to either the 10GBASE-LR4, 10GBASE-XR, or 10GBASE-XW

Here are my specific questions: 

A) What is a SUPI extension?

B) How does a SUPI extension enable the use of the XSBI to "all optical

C) How would the XSBI be used as an optical interface for the
10GBASE-LR4 PHY? Do you have a proposal to do this?

D) What is the advantage of using the 64b/66b PCS for the 10GBASE-LR4
PHY?  Do you have a proposal to do this?

E) What specification/Clause specifies SUPI electrical operation,
specifically the channel model, jitter budgets, transmit eye and receive
eye? I am not aware that this is covered by any clause including Clause
47. In essence, the lower line rate advantage of SUPI is offset by
undesirable characteristics which significantly increase jitter such as
very long and unpredictable run lengths. It appears that no such
specifications exist.

Best Regards,
Paul Bottorff wrote:
> Ted:
> I agree, the two demarcations are XSBI and XAUI.  SUPI is not an interface
> as standardized by IEEE. Instead SUPI supports the 10GBASE-LW4 by attaching
> WWDM to and XSBI interface. The 10GBASE-LW4 WWDM is supported attached to
> XSBI using SUPI, while the 10GBASE-LR4 WWDM can only be supported by
> implementing clause 48 and cannot attach to XSBI.
> Though late for this discussion, it is possible to extend SUPI to allow
> WWDM attachment to the LAN 64b/66b encoder over XSBI. This has three
> advantages: 1)it means all optic modules and modes could be supported using
> a XSBI interface; 2)the transmission frequency of the 10GBASE-LR4 would be
> reduced from 3.125 MHz per lane to 2.578125 MHz per lane; 3)we end up with
> a single 64b/66b PCS layer for all interfaces. Using this scheme XSBI could
> support all optic module types. In addition, the XAUI option would also
> support all types.
> Cheers,
> Paul
> At 01:35 PM 12/1/2000 -0800, Speers, Ted wrote:
> >         I realize this is an implementation question, but is there a likely
> >demarcation point between the transceiver module and the MAC.  It's hard to
> >sort out a lot of these discussions (LSS, XAUI/SUPI, etc.) without have this
> >in proper context.
> >
> >         Possible points of demarcation would seem to be either the XAUI or
> >the XSBI interfaces.  I've seen presentations suggesting both.
> >
> >         It seems that a break at the XSBI would offer the most in terms of
> >end-user flexibility and economies of scale for both the users and the
> >vendors ... with one exception, 10GBASE-X4 would be left out in the cold
> >because, as far as I can tell, there is no way to implement the standard
> >across an XSBI.
> >
> >         Ted Speers
> >         Strategic Marketing
> >         Actel
> Paul A. Bottorff, Director Switching Architecture
> Enterprise Solutions Technology Center
> Nortel Networks, Inc.
> 4401 Great America Parkway
> Santa Clara, CA 95052-8185
> Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365
> email: pbottorf@xxxxxxxxxxxxxxxxxx
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