[e2e] "congestion" avoidance...

Joerg Widmer widmer at informatik.uni-mannheim.de
Mon Apr 23 09:48:52 PDT 2001


> lets assume we now design networks for datagram, with TCP "friendly"
> adaption being the NORM, and that we look at the people that need
> predictable throughput on the session timescale as the odd ones
> out...(predictable price or predictable throughput are natural
> duals of each other in this formulation)
> now if we have _enough_ of these non-adaptive flows, actually, enough
> rate of change of them, they can collectively be made to look like a
> bunch of TCP-like flows quite easily - by varying the admission
> probabiliyu (could do this by increasing the loss or ECN markign
> probability for SYN or RTP equivalent packet - but thats an
> implementation detail, - it could also just be done by varying the
> price differently for these type flows as yo usay - e.g. the ECN to
> price mapping for EF diffserve class might specifiy a different
> fucntion than that for BE and AF, for example:-)
> so then we can cause the aggregate of a set of CBR flows
> to behave exactly like the aggergate of a set of TCP flows just by
> varying the number of flows
> what say we do some analysis...?

We have actually done some work in this direction (Jon you've seen this
already), where an aggregate on non-adaptive flows is made to look like
TCP-friendly flows by suspending them at appropriate times using sort of
a binary end-to-end congestion control mechanism. The technical report
about the PCC protocol can be found at

Since this is work in progress we're very interested in any comments.

  Joerg and Martin

Joerg Widmer
Praktische Informatik IV, University of Mannheim

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