[802.3EEESG] Comments on our work from Vern Paxson
Folks,
I asked Vern, who is well known for his work on TCP, to take a look at
our work and comment on it. Please see his comments below. He has
joined the reflector so I encourage you to ask him questions if you have
any. BTW, outage means packet loss.
Regards,
Mike
Here are my thoughts:
- An outage on the scale of 10s of msec is really no big deal
other than for flows that want to go super fast.
- Presumably, such outages are rare (e.g., a few an hour). If that's
right, then the likelihood of one of these coinciding with a
super-fast flow will generally be quite rare, though obviously
in some environments this might not be the case.
- In addition, I'd think that one would use such bandwidth-switching
in conjunction with network conditions of light load (at least,
when switching to lower bandwidth), which should make a collision
with a super-fast flow even less likely.
- The one case of mild worry is an outage during a switch to
higher-bandwidth, because it's a fast flow that's motivating
the decision to go for higher-speed operation.
- My mental model is that in LANs, s**t happens anyway, i.e.,
it wouldn't surprise me that a few equivalent such glitches
already happen every day, so this isn't seriously altering
the landscape.
- Ken's simulations are fairly natural first stabs, though not
even close to being comprehensive. (And doing it in a comprehensive
fashion would be a *lot* of work.)
- But: my own sense is that there's no need to be comprehensive
for this.
- I don't understand Ken's "PAUSE" control message, but if it's
a layer-2 signal then it requires some careful thought, and
my intuition is it would turn out to be a bad idea (so if the
sense is that this would be *required* for some reason, then
it's time to explore it further rather than proceeding). Related
to this, mention of possibly standardizing in the IETF gives me
considerable pause.
- If you wanted to thoroughly examine these issues, the way to
start would be email among the interested parties (e.g., me & Ken
and whoever else), or, better, on one of the relevant mailing lists.
It's not clear to me from your framing whether such thoroughness
is needed at this point.