[e2e] Question the other way round:

[Vimal]

I think it depends on how you define congestion.

For a simple single-link resource, if you define congestion as "long term
utilisation of a link >= capacity" then in some sense we "need" congestion
as we would like to fully utilise the network (i.e., we want utilisation =
capacity).

If you define congestion as "queue build up at all timescales" then
congestion is inevitable at any load > 0 if arrivals are random.

There has been some work on defining the right operating point of the
network for a certain metric.   For instance, it is known (due to Leonard
Kleinrock as far as I can recall) that the "right" operating point for an
M/M/1 queue to optimise the average throughput/delay^r for flows is to
operate it at a point where the expected queue occupancy is exactly r.

I am not a super expert on this topic, so I am attaching references here:

References:

Kleinrock, L., "On Flow Control in Computer Networks", Conference Record,
Proceedings of the International Conference on Communications, Vol. II,
Toronto, Ontario, pp. 27.2.1 to 27.2.5, June 1978.

Kleinrock, L., "Power and Deterministic Rules of Thumb for Probabilistic
Problems in Computer Communications", Conference Record, International
Conference on Communications, Boston, Massachusetts, pp. 43.1.1 to 43.1.10,
June 1979

Gail, R. and L. Kleinrock, "An Invariant Property of Computer Network
Power", Proceedings of the International Conference on Communications,
Denver, Colorado, June 14-18, 1981, pp. 63.1.1-63.1.5, 1981.




On 15 November 2013 13:42, Detlef Bosau <detlef.bosau at web.de> wrote:

> Why do we need congestion at all?
>
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-- 
Vimal