[e2e] QoS vs Bandwidth Overprovisioning

Michael Welzl michael at tk.uni-linz.ac.at
Thu Apr 26 00:52:14 PDT 2001

> In this vein, has anyone tried to deploy the "Alternative Best Effort"
> proposal of Jean-Yves Le Boudec?
> (http://ica1www.epfl.ch/PS_files/abe.htm). His basic idea is
> that there
> is a simple way to prevent cheating, i.e. provide a trade-off: you may
> get a lower latency if you mark the packets for "alternate
> best effort",
> but you will also get a lower bandwidth. Indeed, the whole
> thing can be
> combined with ECN marking, to trigger adequate bandwidth adaptation by
> the VoIP application, e.g. choice of the right codec and parameters.
> In fact, if we observed a real problem with latency of VoIP, we could
> even implement ABE without requiring any particular marking. Just
> profile the packets that fit the VoIP profile, i.e. short UDP packets,
> or maybe just short packets, and fit them into the ABE queue. If I
> remember correctly, Sandy Fraser had implemented something
> like that to
> provide adequate latency for interactive traffic in the Datakit, and
> reported that it was satisfactory. So, if there is a need, an
> ISP could
> just turn on the service at some choke point, without any particular
> coordination with other networks, or any change in the end systems.

I saw a presentation of Jean-Yves Le Boudec at the QoS Summit '99 (
http://www.upperside.fr/baqos.htm ) and have been wondering why I never
heard of it since. Maybe he just did not discuss it in the IETF?

> On the other hand, in many existing networks, there may just
> not be any
> need for such optimizations...

I don't think so. It would sure be great for VoIP.

Michael Welzl

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