Re: Does tcptrace measure RTT for every ACK?

From: uaca@alumni.uv.es
Date: 11/15/02


Date: Fri, 15 Nov 2002 12:21:37 +0100
Subject: Re: Does tcptrace measure RTT for every ACK?
Message-ID: <20021115112137.GA15919@pusa.informat.uv.es>
From: uaca@alumni.uv.es

On Thu, Nov 14, 2002 at 11:22:23PM -0500, Mark Allman wrote:
>
> > As you know, the TCP measurement is made every RTT, not for
> > every ACK, in the real world.
>
> Depends on which real world you're talking about. Traditionally,
[...]

Have you read this?

On Wed, Nov 13, 2002 at 12:39:57PM -0500, Liangping Ma wrote:
> Hi, Ulisses,
>
> I did TCP RTT measurement before. Based on my memory, the tcptrace
> processes tcpdump raw data, which can be collected in a local ethernet.
> You are right, that the measurement may not be on one of the end points
> of a TCP conneciton. But the delay within a LAN is trivial in the case of
> a long-haul TCP connection. Thus the measurement can be reasonably
> accurate.

Ok, imagine the following two scenarios

<Monitorization Host>
         |
         |
[Host A] >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> [Host B]
         <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

                                                    <Monitorization Host>
                                                             |
                                                             |
[Host A] ))))))))))))))))))))))))))))))))))))))))))))))))))))> [Host B]
         ((((((((((((((((((((((((((((((((((((((((((((((((((((<

If I'm right RTT meassured values differ their meaning _a lot_ depeding
where the monitorization host is

Am I right?

Thanks in advance

        Ulisses

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