Yes, absolutely. It is just like the standard restart-after-idle
problem. I have my "TCP fast start" proposal and others have their
own, but it is unclear what the "right" solution is. And this
is not really be an issue unless we are dealing with networks
with sufficiently large bandwidth-delay products. Few of the
existing networks may qualify on this count, but I suspect the
situation will change before long.
-Venkat
Venkat Padmanabhan
Microsoft Research
padmanab@microsoft.com
http://www.research.microsoft.com/~padmanab
> -----Original Message-----
> From: Ramon Caceres [mailto:ramon@research.att.com]
> Sent: Monday, February 15, 1999 10:08 AM
> To: Venkat Padmanabhan
> Cc: pilc@lerc.nasa.gov
> Subject: Re: LL ARQ on LD links [was: PILC: prioritization]
>
>
> > Date: Mon, 15 Feb 1999 09:39:18 PST
> > From: Venkat Padmanabhan <padmanab@microsoft.com>
> >
> > Your 3-dupacks scheme indeed appears to be an interesting
> > solution that is compatible with the existing TCP standards.
> > However, it seems to me that in the case of a sufficiently long
> > outage, this scheme would not prevent cwnd from shrinking down
> > to 1 segment, ssthresh from halving, etc. (correct me if I am
> > mistaken!).
>
> You're right, but that was a conscious decision. In the
> mobility case we were dealing with, I would argue that you
> want TCP to go into slowstart to probe the congestion state
> in the new cell. That cell is unknown territory.
>
> With a link outage that does not involve motion, slowstart
> may not be what you want but I think it bears discussion.
> My concern is that the congestion state along the TCP path
> may have changed for the worse during the outage. It's
> important for TCP to behave conservatively or risk making
> a bad situation worse for everyone.
>
> We can argue about whether slowstart does a good job of
> utilizing available bandwidth after a link outage, but
> I think that getting TCP out of the long retransmission
> backoff fixes the first-order problem.
>
> --Ramon
>
This archive was generated by hypermail 2b29 : Mon Jan 28 2002 - 09:12:20 EST