Re: hi,

[Kevin Fall <kfall@ee.lbl.gov>]

>
> From:  Biaz Saad <saadb@cs.tamu.edu>
> To:    NS-USERS@mash.CS.Berkeley.EDU
> cc:    XYIN@ecs.umass.edu
> Subject: Re: hi,
> Date:  Fri, 16 Jan 1998 10:56:12 CST
>
> Hi xianghong,
> 
> 	Unfortunately, I did not receive any hint on how to monitor the
> window size. I still do not know how to this through ns.
> 	You can use the tcpdump function (see test-suite demos). But this
> will completely slow down your simulation. Otherwise, you can infer 
> approximatively the window size from the trace files. This can be done
> only if you use the agent FullTCP.
> 	An other solution would be to modify the tcp agent to dump the
> data you want.
> 	I hope that this will help you.
> 								Saad.
> 

There is another way that should work.  You will note that
the cwnd_ variable in tcp is of type "TracedDouble".  This means
you should be able to do something of the following form:

	set chan [open xxx.tr w]
	..
	$tcpagent attach $chan
	$tcpagent trace cwnd_

This will produce a trace file called xxx.tr containing lines
of the following form:

	...
	9.20576  0  0  3  0  cwnd_ 6.263 
	9.21576  0  0  3  0  cwnd_ 6.423 
	9.30576  0  0  3  0  cwnd_ 6.579 
	9.31576  0  0  3  0  cwnd_ 6.731 
	9.32576  0  0  3  0  cwnd_ 6.879 
	9.33576  0  0  3  0  cwnd_ 7.025 
	9.34576  0  0  3  0  cwnd_ 7.167 
	9.35576  0  0  3  0  cwnd_ 7.306 
	...

A line is written each time the variable is changed.  See the
code in tcp.cc (traceVar()) for more info.

- K