[e2e] Estimating MS windows RTO equation

Detlef Bosau detlef.bosau at web.de
Fri Feb 3 03:50:27 PST 2006

sanjay kaniyar wrote:
> Sushant -
> Windows uses the very same algorithms prescribed by the standard RFCs - so,

Sounds interesting :-)

I did not look at the code, but some few years ago the tabloids here in
Germany talked about some "proprietary TCP/IP extensions" 
implemented by Microsoft.

I did not check this myself, I even did not have any opportunity for
doing so.

However, after reading this rumour I´m somewhat suspicious about
Windows. It might be a personal problem of mine.

Anyway. Saying, an implementation uses the very same algoriths
prescribed by the standard RFCs sounds not very sound ;-)
There are dozens of papers around which find flaws in comon TCP
implementations (and I vaguely remember at least one which
did not only discovered flaws in HP UX and Solaris but in Windows NT as
well) and even in this thread here we talked about a project
which dealt with implementation flaws in actual TCP implemenations.

Perhaps the most funny thing in this context is a switch I found in
Linux with which the Linux TCP implementation can be made 
"bug to bug compatible" with BSD :-)

> I would think you should see the results you are expecting... if you are
> not, send a mail just to me and we will work with you.
> And yes, Windows does fast-retransmission upon receiving 2nd dup ACK.

So, we have the first implementation flaw in Windows TCP, haven´t we?
(Assuemd, "3rd" dup ACK is correct, I didn´t look it up myself,
because neither is state of the art. State of the art is the use of a
user / application defined dupackthreshold.

Detlef Bosau
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70565 Stuttgart
Mail: detlef.bosau at web.de
Web: http://www.detlef-bosau.de
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