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Re: 64/66 control code mapping

Dear Ben,

> I've been looking at your 64b/66b presentation and, in
> particular, looking at your control code mapping. The
> 7-bit line code is specific to encodings from the 8b10b
> XAUI interface. This is an optional interface and may
> not exist between all MAC and PCS layers. When the XAUI
> doesn't exist, what 7-bit line codes should be used?

The same linecodes as for XAUI.

A 64/66 coder running off of XGMII needs all the logic of a XAUI encoder
except for the 8b/10b encoders and serializers.  This logic is required to
ensure insertion of Align characters, force SOP to be in lane 1, etc. 

> Given the protocol stack shown by Brad Booth, I would expect that this
> PCS layer be specified to an XGMII and not to an XAUI. 
> Implementations may choose to short- cut the conversion from XAUI to
> XGMII to 64b/66b but the specification should assume it communicates
> to the XGMII. 

XAUI can be thought of as an optional XGMII extender.

64/66 is probably best thought of as optional XAUI physical layer. 

64/66 replaces XAUI's 4x3.125Gb/s physical layer with a single 10.3Gb/s
serial fiber link.  In the same way, WWDM or parallel fiber solutions
can be thought of as optional XAUI physical layers. 

This may not be consistent with 10GbE's rigorous taxonomy of layers, but
I think it is a self-consistent way to describe the situation.

If you want to discuss this further, we should probably move to the 64/66b
reflector at:


I've replied both to the main hssg reflector and to the 64/66 address.