[Ns-developers] bug in tcp.cc?

[Xiaoliang "David" Wei]

Hi Andres,

   You are right on what is in the code. But why do you think this is a bug?
I think wnd_ is the maximum window size for a TCP connection. So, setting
slow start threshold to wnd_ effectively allowing the slow start goes to the
maximum window size.

   (Yes, I am not sure why wnd_ has a default value of 20 in the first hand
though...)

-David

On Tue, Feb 5, 2008 at 1:17 AM, Andrés Arcia <ae.arcia at telecom-bretagne.eu>
wrote:

> Greetings,
>
> I think there is a bug in the initialization of the slow start
> threshold for TCP (at tcp.cc). If you simply try this code you'll
> reproduce it:
>
> $ ns-2.30
> % set ns [new Simulator]
> _o4
> % Agent/TCP/FullTcp set ssthresh_ 1000
> 1000
> % set save [new Agent/TCP/FullTcp]
> _o11
> % $save set ssthresh_
> 20
>
> The problem may be at the TcpAgent::reset() method in:
>
> ssthresh_ = int(wnd_);
>
> Since each variable have a TCL bind, the direct setting of ssthresh_
> does not represent a problem and then it is silently overwritten in
> reset() at the instantiation of a TcpAgent.
>
> Thanks,
>
> --
> Andrés Arcia
>
>
>
>


-- 
Xiaoliang "David" Wei
http://davidwei.org
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