Abstract

Congestion control for heterogeneous sources: strategies and cooperation.

Peter Key
Microsoft Research

Much current research into Internet congestion control has focussed on so-called
elastic traffic, which can adapt its sending rate arbitrarily, and which is also
insensitive to latency.
For many applications, one or both of these assumptions may be violated. For example,
streaming media requires a minimum rate (goodput) to give an acceptable user experience,
while real-time interactive applications are sensitive to delay.
An interesting question is to what extent service differentiation is
possible without partitioning the network in a hard or soft manner.
Stimulated by talk of web mice and elephants, we consider how to share
bandwidth between transient flows, and long-lived or persistent flows.
Informally, transient flows are those which have a fixed volume of data to transfer,
while persistent or long-lived flows either persist or last for a fixed-time
independent of their sending rate. By considering an associated optimisation
problem, we show that for this scenario it is possible to find a decentralised solution,
which requires minimal network support. In effect, this implements a form of
weighted processor sharing, and that can approximate the shortest-remaining
processing time discipline.
We then look more closely at certain specific types of long-lived flows, and
consider applications which can only switch between a fixed number of sending-rates,
and must send above some minimum rate. They adapt their rate by occasionally
measuring or probing the network. For these applications, by appealing to
limiting functional central limit results, we show that for moderately sized networks
minimal probing is needed and hence minimal change of rate by the application.
Questions of fairness with elastic traffic are handled by adaptation and by the
application occasionally not entering the network, rather than by mimicking
the behaviour of elastic traffic.

References:

S. Deb, A. J. Ganesh and P. B. Key href="http://research.microsoft.com/scripts/pubs/view.asp?TR_ID=MSR-TR-2001-114">Resource
Allocation with Persistent and Transient Flows
MSR Technical Report, MSR-TR-2001-114.
Revised version to appear in Networking 2002.

Alan Bain and P. B. Key href="http://research.microsoft.com/users/pbk/Papers/mama.htm">
Modelling the Performance of Distributed Admission Control for Adaptive Applications
MAMA Workshop, June 2001, Performance Evaluation Review.

Peter Key and Laurent Massoulié href="http://research.microsoft.com/research/network/publications/ISQElm.ps">
User policies in a network implementing congestion pricing
Workshop on Internet Service Quality Economics (ISQE), December 1999.