Wireshark-users: Re: [Wireshark-users] FW: Merging files duplicate acks &retransmissions
Hi Martin,
The "Compare" stat doesn't seem to make much difference other than halving the number of packets when you filter on one direction only. I would really like to see your documentation, when you have tried it. I'm sure that I don't fully understan the start & stop and info packet display numbering, once the compare has run.
Keith French.
________________________________
From: wireshark-users-bounces@xxxxxxxxxxxxx on behalf of Martin Visser
Sent: Thu 27/05/2010 23:02
To: Community support list for Wireshark
Subject: Re: [Wireshark-users] FW: Merging files duplicate acks &retransmissions
>From reading http://wireshark.askapache.com/lists/wireshark-bugs/200806/msg00042.html it would seem you might be best filtering traffic only coming from one direction before merging (It's a feature I might need to try out and document properly. It would seem to be mostly useful for detecting dropped packets).
Regards, Martin
MartinVisser99@xxxxxxxxx
On Fri, May 28, 2010 at 7:42 AM, Martin Visser <martinvisser99@xxxxxxxxx> wrote:
If you merge two cap files of effectively the same data you without doing any other pre-filtering you are going to have a lot of TCP segment pairs having the same SEQ and IP address/ports. Wireshark (as it emulates what a TCP would "think") will by definition interpret them as dups, windows updates and retransmissions depending on the order that the merge produces.
(I haven't seen the compare feature as yet so I am unsure whether you are doing this the right way)
Regards, Martin
MartinVisser99@xxxxxxxxx
On Thu, May 27, 2010 at 8:03 PM, Keith French <keithfrench@xxxxxxxxxxxxx> wrote:
Sorry in my first email I forgot to state the mergecap syntax I was using. It is:-
mergecap -F libpcap -w merged.pcap client.pcap server.pcap
Where "client.pcap" & "server.pcap" are the traces from either end of the connection and "merged.pcap" is my resulting merged trace.
Keith French.
________________________________
From: Keith French
Sent: Wed 26/05/2010 15:32
To: wireshark-users@xxxxxxxxxxxxx
Subject: Merging files duplicate acks & retransmissions
I have two capture taken on two laptops at either end of a client/server scenario. I want to merge them to use later with the new compare feature on Wireshark's Statistics menu. Neither trace has any TCP analysis flags set, other than a few window size updates & 1 retransmission.
However, when I merge them with Mergecap chronologically, I end up with about 400 TCP window size updates, duplicate acks & retransmissions etc.
I have tried this on several different trace scenarios and get similar results. Why doe this happen?
Keith French.
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