The discussion about a MAC/PLS pacing mechanism would be more
important if the interface were typically exposed. If it is
not exposed (and that's my guess), how it works is an internal
implementation issue. The PHY would clock information from the upper
protocol layers however it needs to.
This would simplify the discussion and eliminate the question of
how 802.3x interacts. Use of the 802.3x mechanism in this pacing
AND allowing flow control from the other end of the link probably
conflicts with the assumption in 802.3x that flow control packets
are not forwarded. As observed previously (Mick Seaman?), generating
such packets at the MAC/PLS interface AND forwarding such packets (without
extra internal state) received from the link can cause confusion.
The "bit time" used in the various calculations (IFG, 802.3x pause..)
can be defined at 10G or some other standard rate, probably with less
Still, the question of a THROUGHPUT RATE TARGET interacts with
the signaling rate and packet formating to be used on the link.
Leveraging the OC-192 equipment still requires defining the packet
formating, and without flexibility in the signalling rate we have to
work on tradeoffs in the framing/formating vs throughput.
It seems to me that the leverage from the OC-192 deployment is mostly in the
regenerators. Current SONET ADMs would do not transport OC-192c trib
The current LINE side is about 10Gb/s so there's no multiplexing or
The OC-192 components are ahead in volume right now, but the prospects
for 10Gb/s Ethernets would provide enough volume on their own to justify
tweaks to the component specifications, assuming no attempt is made
to push the performance 25%. The other advantage of the defined OC-192
structure is the overhead already reserved for link performance monitoring.
This saves definition work if this style of OAM&P is desired for extending
the reach of 10 Gb/s Ethernet using the deployed SONET OC-192 regenerators.
Overall, if you believe in significant 10Gb/s Ethernet volumes, leveraging
the deployed OC-192 regenerators is useful but not compelling. On a
of new links, new regnerators that clock at a slightly different clock
rate can be installed as well as old design regenerators that do exactly
what SONET OC-192 defines. Within the 40km target, regeneration would
not typically be used at all. Maybe making the physical layer
work with EDFAs will be more important than with OC-192 regenerators.