TCP and Loss


Craig Partridge (craig@NNSC.NSF.NET)
Fri, 02 Oct 87 15:09:31 -0400


Thomas,

The work I was doing on RDP led me into the problems of how transport
protocols perform in the face of loss. I haven't had much time to
look at the problem recently (I'm doing this in my spare time -- and
don't have much) but keep plugging away.

I'm interested in situations in which loss is inherent -- that
is, you will get loss, no matter what your TCP does. Packet radios
suffering from noise or jamming are good examples. Loss caused by
congestion is a different problem.

The paper Phil Karn and I gave at SIGCOMM touches on the problems. Karn's
algorithm is a method for keeping an accurate round-trip time estimate
even when loss rates reach 50%.

Currently I'm seeing if I can model what happens to acknowledgement and
transmission strategies if the loss rate really climbs. So far I
know that there are situations in which at least some strategies to
reduce the number of acks you send fail *big* under loss -- you get
more total packets sent than if you had had sent the acks you suppressed.
Beyond that I don't have anything to say yet -- I'm finding the mathematics
of it difficult.

I'd be interested to know of other people working in this area.

Craig



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