[Iccrg] Re: flow completion times in uncongested systems

[Lachlan Andrew]

Greetings Sally,

On 05/11/2007, Sally Floyd <sallyfloyd at mac.com> wrote:
> > - The rise time of a single flow to an empty systems is not very
> > interesting, because it many measures the impact of slow start.
>
> Actually, the flow completion time in an uncongested system can be
> a quite interesting thing to measure, particularly if one is
> evaluating one of the many proposals for start-ups faster than
> slow-start.  (One of these proposals is Quick-Start, RFC 4782; some
> of the others are discussed in Appendix A of RFC 4782.)

True.  I should have said that this is a very different quantity from
the responsiveness of the algorithm to control the window after slow
start.  As you say, it is of independent interest.

> I would recommend having scenarios include the case of a
> generally-uncongested link, as well as including cases with various
> levels of congestion, with metrics including per-flow transfer
> times, fairness, and aggregate packet drop rates.  This should
> illustrate some of the good and potentially-bad aspects of protocols
> with fast start-ups.

Yes, testing a range of levels of congestion is good.  My concern was
that we should not just measure the performance of a post-slow-start
modification by observing slow-start behaviour.

Cheers,
Lachlan

-- 
Lachlan Andrew  Dept of Computer Science, Caltech
1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA
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