[dccp] feedback on draft-ietf-dccp-tfrc-media-00.txt

[Sally Floyd <floyd at icir.org>]

Tom -

This is a very helpful and thoughtful document!  A few nits below,
about the possibility of a higher initial window; mentioning ECN
in a few more places; and the response to an idle period.

Many thanks!

- Sally
http://www.icir.org/floyd/

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Slow-Start:
One possibility mentioned in the appendix of CCID 3 is to allow
an initial window of up to eight small packets, up to 4K bytes,
instead of the current initial window of four small packets.
(It is mentioned as possible future research, however, not
standardized...)


Capacity Probing and Lost Packets:  
I think it is worth says here "lost or ECN-marked packets",
just to make it clear that with ECN at the congested
routers, there don't have to be any packet losses.

I would recommend the same in Section 4.1, where it says
"This means that packet loss will likely be routine with this
strategy."  It is worth explicitly acknowledging that an 
ECN-capable router would change this.


Idleness Penalty:
"If the transmitter goes idle for a few RTTs, as it would if, for
instance, silence suppression were being used, the transmit rate
returns to two packets per RTT,"

I would clarify to say that the allowed transmit rate is halved
for every 4 RTTs of idle time, and that the allowed transmit rate
is only halved when it is at least four packets per RTT (so that
it is never halved to less than two packets per RTT).

This could be corrected in Section 4.3.2 as well.