Re: Problem running FTP over TCP

[Subhasree Mandal <subha@cse.ucsc.edu>]

Actually, I observed the cwnd_ (congestion window) also.  That goes to 0,
which seems to cause the problem.  I need to find out whether that is
allowed by TCP with ECN capability.

 On Sat, 17 Jul 1999, Sharon Strelitz wrote:

> 
> Hi Subhasree -  Could that connection be suffering from congestion and
> its sender is backing off?  Perhaps that connection is being discriminated
> against without RED gateways which are more fair.  You could test this
> by increasing the bandwidth of the connection to ensure no congestion
> and see if it still happens.
> 
> Sharon
> 
> On Fri, 16 Jul 1999, Subhasree Mandal wrote:
> 
> > I was running a configuration with a bunch of FTP connections on TCP.  In
> > one particular case one particular connections sends its last packet at
> > time 19.34137 sec and does not send any more data after that, though the
> > simulation runs till til 40 sec.  The commend used to run this FTP was
> > 
> > $ns at 1.41 "$ftp12 start" 
> > 
> > the following were the last few lines of the sequence number trace
> > 
> > 18.91257 4607
> > 18.91310 4608
> > 18.94483 4609
> > 18.94483 4610
> > 18.97710 4611
> > 18.97737 4612
> > 19.00937 4613
> > 19.30937 4611
> > 19.30937 4612
> > 19.34137 4613
> > 
> > What may go wrong with it?
> > 
> > If I change the start time to 1.45 say, the problem vanishes.  I had ecn
> > gateways, in this case.  If I use RED (with drop) instead, I do not face
> > the same problem.
> > 
> > subha
> > 
>