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Re: XAUI and 64b/66b


There seem to be a couple of "non-typical" reasons why
we want to carry the XAUI encoding across the 64b/66b, in
particular a & b below. I'd like to see more on c & d
before I pass judgement on whether these functions require
XAUI encoding to be supported.

Rich Taborek wrote:
> Support of control information during the IPG for Ethernet. This would include:
>   a) Desirability for common components with FC, InfiniBand, etc.;
>   b) Support of Layer 1 signaling for Optical Cross-Connects and management
> thereof ala Mr. Osamu Ishida's Albuquerque proposal;
>   c) Support of Layer 1 signaling enabling functions such as Remote Fault and
> Break Link to allow the prompt failover protocols (e.g. Busy Idle or
> Ordered-Sets);
>   d) Possible support of Open Fibre Control protocols;
>   e) Support of XAUI codes in the absence of the XGMII without having to revert
> to RS codes.

As for e (above), this wouldn't be necessary if my proposal was
supported. What I'm saying is:

Transmit PCS supports either XAUI or XGMII encodings.

Receive PCS must be able to interpret both encodings and optionally
convert XAUI encodings to XGMII encodings if an XGXS is not present
at the interface or convert XGMII encodings to XAUI encodings if an
XGXS is present at the interface. Perhaps some of these functions
are supported by the XGXS itself, that depends on where we draw the
line in writing the standard.

Are you in support of such a method or is your position that 64b/66b
should always carry XAUI encodings only, regardless of whether a
XAUI is present? Presumably, if this is your position, then the
transmit PCS (when there is no XAUI present) would have to support
all the randomness in regards to /A/ and /R/ that you're proposing
so at the receive side, should a XAUI be present, the translation
from 64b/66b to XAUI is direct.


Benjamin Brown
Router Products Division
Nortel Networks
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Kilton Road
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