Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: Data rate standards vs internal switching standards


Just a quick reappearance to address your follow up questions.

> I would like an additional clarification. In recognizing that the data
> clocking standards are at the exposed interface of the data link, does
> this mean that the standard applies to the MII between the MAC layer
> and the PHY or does it apply more to the PHY?

You have examples of both. The MII/GMII case is obvious.

Other exposed interfaces were defined within the PHY to reflect real
life partitioning into:

- Clock recovery being the realm of exotic circuits designed by long
haired gurus that seldom show up for work before 11 A.M.

- The coding layer, can go into CMOS based MAC ASICs, and can be
designed at any time of the day by many mortals skilled in the art of
digital design.


> As for the OC rate standard, there are several standards for mapping
> data into SONET/SDH transports. From an 802.3 view point, the
> SONET/SDH standards can be treated as layer 1 functional processes.
> From the other side of that argument, the current packet over SONET
> (POS) standard for mapping required an additional standard for
> inserting a layer 2 functionality between the layer 3 IP protocol and
> the layer 1 SONET protocol. 802.3 does not have that requirement for
> an additional functionality. In many ways it is more of a question of
> how much of the SONET/SDH standards would not used for 10GbE,
> depending on the implementation of the interfaces. 

My emphasis was that the optimization of the data rate to is
specific for a particular mapping and cannot be adopted in isolation
unless such mapping is also embraced.

Finally, I hope that your lack of objection to a 10Gbps rate with a
statically programmable IPG is somehow a sign of agreement.

> Thank you,
> Roy Bynum
> MCI WorldCom


Ariel Hendel 
Sun Microsystems