[ns] goodput calculation?

["Xiaojun Cao" <xjcao@263.net>]

Hi, ns-users,
I have read all previous discussion on Good Calculation? But I am still
confused which is the correct method.  I just want to calculate the goodput
for the whole system. So it should exclude the duplication packet which
maybe is a retransmission. Can I get this in following way:
    Parse trace file, goodput=sum (all received TCP packets) - sum (received
TCP packets have flag of "---A---")
    received TCP packets:  TCP packets whose event is "r "

I dont think this is right. but how can I get to know a received packet is a
retransmission of previous received packet from the trace file.  It seems
that they should have same sequence number. If so, how to use perl or awk
deal with the trace file? That also means perl script should  compare it
with all previous sequence numbers which the perl script have parsed?  ...?
Is there any better way to get goodput?

Thanks
X. Cao