[e2e] end2end-interest Digest, Vol 17, Issue 26
nicolasc at andrew.cmu.edu
Thu Aug 4 07:59:50 PDT 2005
On Wed Aug 03, 2005, Detlef Bosau <detlef.bosau at web.de> wrote:
> Do you think, there´s a way to do so, thereby maintaining the typical
> "packet-switching best effort" nature of the Internet?
> Perhaps, this is a borderline between "best effort" traffic shaping (if
> this even exists) and some kind of guaranteed service. I really don´t
> know yet.
I actually studied a very related problem in the good ol' days of my
Ph.D dissertation. I basically tried to combine buffer management and
packet scheduling to provide service differentiation without admission
The trick is essentially that the bounds that you give to traffic
classes are actually soft, in that they can be violated. (Keshav is
completely right - when traffic is really bursty, it is very difficult
to do any type of intelligent predicition, and you might end up with
something that is not much better than best effort.)
The good news is that you can do quite a lot if you combine scheduling
with packet dropping, and even more when you start looking at ways to
playing with TCP congestion control to do essentially endpoint admission
control for you.
If you are interested, a summary of my dissertation is in:
N. Christin and J. Liebeherr.
A QoS Architecture for Quantitative Service Differentiation. In IEEE
Communications Magazine 41(6), Special Issue on Scalability in
IP-Oriented Networks, pages 38-45. June 2003.
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