[e2e] end2end-interest Digest, Vol 17, Issue 26

Detlef Bosau detlef.bosau at web.de
Wed Aug 3 15:20:53 PDT 2005

S. Keshav wrote:
> The easiest way to make the queueing delay constant, or nearly so, is to
> introduce wait times where the link is idle even though there are packets in
> the queue. This reduces delay jitter in the system and makes the whole
> network more circuit-like. By introducing new 'work', the system is what is

Exactly. And I´m not quite sure whether it´s that what I want to do.

> called 'non-work-conserving'. Such systems were studied extensively in the
> early 90's. For more details, you should look up Hui Zhang's comprehensive
> survey on scheduling: "Service disciplines for guaranteed performance
> service in packet-switching networks" Proceedings of the IEEE, Volume 83,
> Issue 10,  Oct. 1995 Page(s):1374 - 1396.
> hope this helps

It exactly marks the problem.

The more circuit like a network is, the less are the economical 
advantages for typical "packet switching users".

When we make a delay´s _expectation_ constant for a certain amount of 
time, we can well accept a large variation. Jitter is not the problem. 
So, this could be overkill here. However, I don´t know of a "weaker" way.

In my other post from today (Augst, 3rd) I tried to weaken the problem 
that way, that I only ask for a limited forecast capability. It is not 
necessary to keep a queueing delay constant or makeing it obey a certain 
distribution. It would be sufficient to forecast its expectation, and if 
possible its variance, for a limited period of time, e.g. 200 ms.

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.

Detlef Bosau
Galileistrasse 30
70565 Stuttgart
Mail: detlef.bosau at web.de
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