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All, John encouraged me to restart the discussion thread (ref: my
old e-mail titled “Question” sent to the previous hssg reflector we
used) regarding topics we may want to put on the agenda for the next meeting(s). Please add to this. Here it is with one addition at the end:
For example: (a) Technical feasibility of a 100 Gb/s (or whatever
speed we choose) Medium Access Control function is a topic that justifies more
discussion than we had so far. I hope we can see some presentations that will
go further than just saying “higher clock speeds and wider data path”
make this feasible. Should we look at the feasibility of implementing the CRC
function, for example, at this speed? (b) Technical feasibility/aspects of Physical Layer
Aggregation. Perhaps there are no issues here and for some this is trivial.
However for many people in the study group and 802.3 WG this isn’t
“intuitively obvious”. A minimum size packet at 100Gb/s lasts about
5 ns. That is about the same as the propagation time through 1 meter of cable.
If we look at a 1 Km link we could have 1000 packets in transit (or 10,000
packets on a 10Km link and many more on long haul links coast to coast). What
is the skew we would allow between lanes? How do we reconstruct the packet
which traveled 10 Km on 10 lanes? Again, I am sure there are a few among us who
have all the answers but we need to educate the entire group so eventually we
can vote yes on technical feasibility. (c) Compatibility. Are there higher layer
implications to the fact that on a long distance 100 Gb/s link we will have 10
x the number of packets in transit (e.g. retransmission windows)? (d) Economic Feasibility. There seems to be a lot of
support to reuse the 10Gb/s PMDs. That may indeed end up as a good choice but
before we make such a choice, would it be worthwhile to discuss the merits of
1500 nm vs. 1300 nm optics as this relates to packaging 10 x 10 Gb/s xcvrs into
one physical device? Perhaps there are fundamental economic feasibility
differences between the two (I am not saying that there is or there
isn’t)? (e) On the topic of distinct identity. The
fundamental assumption for this study has been that Equal Cost Routing and
802.3 Link Aggregation are not good solutions for point to point routes that
require greater than 10 Gb/s. Since this is at the basis of justifying our
study group I believe it would be beneficial to listen to some presentations
(tutorial in nature) on these two approaches (what is it, how it works in
practical terms when a network manager sets this up and more details about why
these techniques are not as good as we would want them to be). (f) Another technical feasibility and economic
feasibility related topic is Forward Error Correction. It would be great to
hear about tradeoffs in implementing FEC on the individual lanes (NxM FEC
implementations) versus at the new high speed (e.g. at 100 Gb/s) Cheers, Menachem
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