Re: [ns] Pairing a send and a corresponding ack - 2

["Alvaro Armenta" <aarmenta@cicese.mx>]

I bealive that when a TCP retransmision is made,
that new packet_id is created, but the seq_no is
not modified. The seq_no is the same for the packet lost.

regards

�lvaro Armenta
----- Original Message -----
From: "Meera Jayaram" <meera_jayaram2001@yahoo.com>
To: <ns-users@isi.edu>
Sent: Wednesday, July 25, 2001 1:16 PM
Subject: [ns] Pairing a send and a corresponding ack - 2


> Hi folks,
>
> I posted this query quite sometime back and could not
> get an answer which would help me proceed.
>
> Hence, I will try to explain my question again in more
> detail. I hope someone can point me in the right
> direction this time.
>
> I am trying to find out if there is a way to pair the
> send/forward events to their corresponding
> acknowledgements. I am doing a tcp based wireless
> simulation run where I am trying to find the various
> paths followed between source and destination for each
> and every flow and also for how long each of these
> paths lasted.
>
> I am kind of stuck at this stage where I am trying to
> pair the ack with the send. It seems
> that the ch->uid()(packet Id) and sequence
> number(th->seqno_) have no relation execpt that they
> form an increasing sequence.
>
> When there is a retransmission due to timeout, we have
> a new packet Id and seqno for this retransmitted
> packet. Is there any way to find the original packet
> Id and seqno of the packet corresponding to which the
> retranmission is taking place (i.e what is the packet
> Id or sequence number corresponding to the original
> data packet for which this retransmission is taking
> place!) Even if its not possible to get this info by
> looking at the trace, can I determine this from some
> part of the source code??
>
> The reason I need this is because my application needs
> to determine the amount of time for which a particular
> path lasted since I am measuring the quality of a
> protocol in the mobile simulation. Hence it is very
> important that I detect the retransmissions and the
> time at which the paths changed correctly. I have
> examined the sources tcp.h, cmu-trace.h etc and I
> cannot seem to find where exactly the following
> information can be obtained.
>
> Eagerly anticipating some help.
>
> Thanks in advance.
>
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