[Ns-bugs] [Bug 1351] New: TCP not able to take RTT samples on long delay network

[code@nsnam.ece.gatech.edu]

https://www.nsnam.org/bugzilla/show_bug.cgi?id=1351

           Summary: TCP not able to take RTT samples on long delay network
           Product: ns-3
           Version: pre-release
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P5
         Component: tcp
        AssignedTo: adrian.sw.tam at gmail.com
        ReportedBy: tomh at tomh.org
                CC: ns-bugs at isi.edu
   Estimated Hours: 0.0


(reported here on ns-3-users list:
http://groups.google.com/group/ns-3-users/browse_thread/thread/3d788c5c01bf9d6a)

I was using NS to test TCP congestion control variants. Since last week decided
to migrate from NS-3.10 to NS-3.13.
On NS-3.13 I am having several problems with the evolution of the TCP's
congestion window (the results are totally different in NS-3.10 and NS-3.13).
As far i could see when there is high delay (250 ms or more) on the simulated
network TCP is not able to take RTT samples, and due to this is not able to
calculate RTT estimation and the RTO (congestion window is restarted to 1MSS
very often).

The network i have been simulating is simple:

n0  ============== n2 ----------------  n2 ==============  n1
              csma                       p2p                       csma

n0 is the source node (onoffapplication)
n2 and n3 acts as router and implements droptail queue , p2p delay is set to
250ms
n3 is the sink node (sink application)

Attached to the email are the graph of the congestion window on n0 for NS-3.10
and NS-3.13

Is there any bug related to RTT calculation for NS-3.13?

Regards
Mauro Viudotto

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