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Admission Control and Rate Adaptation
Communication networks carry a mixture of elastic traffic, such as
Web downloads, and inelastic real-time traffic. For the latter,
quality degrades appreciably below a specified throughput and so
bandwidth sharing is inappropriate. It is preferable instead to
accept such traffic only when it is possible to guarantee that it
receives a specified bandwidth for a specified duration. Rather than
do this in a centralized manner, we study a decentralized solution,
where a call or flow probes the network and decides whether to admit
itself on the basis of these measurements. More generally, a flow
may choose among a small set of rates on the basis of network
measurements.
Specific scenarios were are considering are
- A home network, where a request is made for an interactive videoconference or
retrieving stored multimedia (eg from a jukebox) and we wish to know if is
possible to grant the request with neither a central controller nor a
reservation protocol. The end-system have to quickly make a yes-no decision,
using existing infrastructure. We are also considering future scenarios
where rudimentary priorities may come from the use of 802.1p/q switches.
- The WAN / Corporate Intranet, where we wish to run a delay sensitive
application (eg VOIP, video conference) and want to have in essence a
distributed light-weight signalling solution. For some of this work we assume
that routers/ firewalls can signal incipient congestion by setting the ECN flag.
- Creation of a "lower than best effort" service,
e.g. for background transfers,
where we need have minimal effect on foreground flows.
As a by-product of this work, we are looking at what statistical techniques can
say about inferring properties of a network from measurements (eg RTT, link
capacity, spare capacity, characterising cross-traffic etc).
The image above (presented at WinHEC 2003) shows the typical scenario
in the home where admission control probing can help ensure a good user
experience for networked multimedia. This is work done in collaboration
with the Windows Home Networking team during 2003.
We have extended our work to investigate adding congestion awareness
to networked applications such as those used for conferencing and media streaming:
This is work done in collaboration with the Windows Microsoft Live
Communications Group and in consultation with the Windows Digital Media
Division team during 2002.
Network Aware Applications: A Background Transfer
Service, Peter Key, Laurent Massouli and Bing Wang,
Forty-First Allerton Conference on Communication,
Control, and Computing, Allerton, October 2003
Network characteristics: modelling, measurements and
admission control, Dinan Gunawardena, Peter
Key and Laurent Massouli,
IWQoS 2003, Monterey, June 2003.
A network flow model for mixtures of file transfers and
streaming traffic, Peter Key, Laurent
Massouli, Alan Bain and Frank Kelly.
Microsoft Research Technical Report,
MSR-TR-2003-37. ITC 18,
Berlin, 2003.
Probing strategies for distributed admission control in
large and small scale systems, Peter Key and Laurent
Massouli.
PDF(procedings version) , IEEE Infocom,San Francisco
2003).
Service-Differentiation for Delay-Sensitive
Applications: An Optimisation-Based Approach,
with Laurent Massouli and Jonathan Shapiro, Proceedings
of IFIP Performance 2002 conference, Rome September
2002. Final version in Performance Evaluation,
2002, Vol 49, pp 471-489. see also
short version.
Modelling the Performance of In-Call Probing for
Multi-Level Adaptive Applications, with Alan Bain
(Stats Lab, Cambridge), Microsoft Research Technical
Report, MSR-TR-2002-06, Jan 2002,
PDF ,
Postscript
Feedback and bandwidth sharing in networks, A. J
Ganesh, P. B. Key and L. Massouli.
Proc. 39th Annual Allerton Conference on Communication,
Control and Computing, 2001.
Resource Allocation with Persistent and Transient Flows
S. Deb, A. J. Ganesh and P. B. Key,
MSR Technical Report,
MSR-TR-2001-114.
Modelling the Performance of Distributed Admission
Control for Adaptive Applications Alan Bain and P.
B. Key,
MAMA Workshop, June 2001.
Distributed Admission Control, F. P. Kelly, P. B. Key and S. Zachary. J.
Sel. Areas Comm., 2000.
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Distributed Admission Control and Congestion Pricing, P. B. Key,
Workshop on Pricing and Quality of Service, Paris, 1999.
PowerPoint.
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