[e2e] link between Kelly's control and TCP's AIMD
Sireen Habib Malik
s.malik at tuhh.de
Tue Feb 22 02:28:22 PST 2005
I just want to continue on the comment that "(tcp) performance modelling
have had some interesting errors". I take this as a very good chance to
understand a few things here.
Following is the most basic model (I am starting with the abc... which
is a very nice place to start).
Area under the curve assuming periodic "packet loss" (AIMD control)
a. total_packets = (w*w)/ 4+ (w*w)/8 = 3*w*w/8
b. loss probability (p) = (1 lost packet) /(total_packets) = 8/(3*w*w)
Therefore, w= sqrt (8/(3*p).
Since average_window = (3*w)/4, therefore,
average_window = sqrt (1.5/p).
Risking the nausea of many people here, i have included all the trivial
steps. This very straight forward approach does lead to a non-linear
What are the errors in this approach?
I am sure that knowing the problem with this one will lead to a deeper
understanding of the "Troubled" Control Protocol (excuse my twist but
the preceding discussions do give the impression!)
Thank you for the response.
>Ooooh Ted, right through the heart! Other papers I have read on similar TCP
>C later admitted to, but
>I promise to take some time to check the ones you suggest.
>Ted Faber wrote:
>>On Sat, Feb 19, 2005 at 12:00:23AM -0800, Cannara wrote:
>>>I don't know "ignored" -- some friends (NetPredict) have a patent on just such
>>>statistical analyses applied to TCP performance products. It's the
>>>nonlinearity that makes any linear differential modelling grossly approximate.
>>>We have to remember some fundamentals -- at least that fluids are variously
>>>compressible & reorderable, unlike packets, and loss of molecules is not an
>>I was going to ask if you'd even read the papers. Thanks for answering
>>http://www.isi.edu/~faber PGP: http://www.isi.edu/~faber/pubkeys.asc
>>Unexpected attachment on this mail? See http://www.isi.edu/~faber/FAQ.html#SIG
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Sireen Malik, M.Sc.
Hamburg University of Technology,
FSP 4-06 (room 3008)
21073 Hamburg, Deutschland
Tel: +49 (40) 42-878-3387
Fax: +49 (40) 42-878-2941
E-Mail: s.malik at tuhh.de
--Everything should be as simple as possible, but no simpler (Albert Einstein)
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