Wireshark · Wireshark-users: Re: [Wireshark-users] wireshark and RTT

[Martin Visser <martinvisser99@xxxxxxxxx>]

Simone,

Way back about 4 years ago, when I was doing an application response time assessment, I also found some inconsistencies in the way that Wireshark sometimes calculated RTT. The main issue was that it didn't always correctly associate the appropriate ACK with right SEQ. I'd probably want to look at the specifics of what you are seeing to see if it was the same problem I was observing. For what it is worth, my post from 2009 is here :- http://www.wireshark.org/lists/wireshark-users/200906/msg00068.html

Martin

Regards, Martin

MartinVisser99@xxxxxxxxx

On 27 August 2013 17:52, Simone Ferlin-Oliveira <ferlin@xxxxxxxxx> wrote:

Hi,

I am capturing traces at client and server and only transferring in downlink, download (s->c) direction. 

I am plotting different things about these flows - window size, rtt, etc.

Depending on the plot, either one trace file or the other is appropriate, but even like this, wireshark shows sometimes very uncommon RTT values. I compare them with tcptrace to validate. I know approximately in which range they should be and

sometimes wireshark shows different values compared to tcptrace -Z ... . I am relying on tcptrace for now. captcp was another

option, but since I capture only 150B for each packet. The tool has a small bug because it accepts only full packets. I modified

the code, but the calculations are wrong since it considers full packet sizes only...

On 26 August 2013 15:37, NITIN GOYAL <nitinkumgoyal@xxxxxxxxx> wrote:

On Mon, Aug 26, 2013 at 6:53 PM, Simone Ferlin-Oliveira <ferlin@xxxxxxxxx> wrote:

Hi, I am doing a download from server to client and I want to see the RTT estimates.

Why is that so complicated? :)

Thanks for the link, but there is no conclusion there, right? What was the conclusion of your discussion with the wireshark forum people?

I did not got conclusion as I was capturing at the client end and it didnot have the access to the server to take the reverse values to validate.

It is not complicated but it is like how exactly you are taking the captures. IF you say the RTT value is not convincing, how you say they are not? Actually there are other ways/tools to validate the values.

Like you can capture the trace and put the trace with the help of tcptrace tool which also calculate the RTT.

Also, you can take reverse RTT calculation frm the server and validate if that will work for you.

For me, i did like that with the help of tcptrace i was getting a bt different values then showed by wireshark which looked convincing to me.

Regards

Nitin

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