tcptrace RTT caltulation

From:
Date: 11/13/02

• Next message:
• Previous message:
• Next in thread:
• Reply:
• Reply:
• Messages sorted by:

---

Date: Wed, 13 Nov 2002 21:22:25 +0100
Subject: Re: tcptrace RTT caltulation
Message-ID: <[e-mail]>
From: 

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

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

                                                    
                                                             |
                                                             |
[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

>
>
> Liangping
>
> On Wed, 13 Nov 2002 wrote:
>
> >
> > I have read rexmit.c:rtt_ackin() and I belive that RTT meassurement is the
> > following:
> >
> >
> >
> > |
> > |
> > [Host A] ))))))))))))))))))))))))))>>>>>>>>>>>>>>>>>>>>>>>>>>> [Host B]
> > ((((((((((((((((((((((((((<<<<<<<<<<<<<<<<<<<<<<<<<<<
> >
> >
> > ")" or ">" is the data segment
> >
> > "(" or "<" is the ACK segment for the corresponding data segment
> >
> >
> > Where the time meassured for RTT is the time that is the sum of ">" and "<"
> >
> > I suposse here the monitorization is being done in the "middle" of the connection
> >
> >
> > That is, tcptrace's RTT is not like the RTT meassured in the "ping" utility,
> > in other words is not a "two full way transmision" meassurement
> >
> >
> >
> >
> > Thanks in advance
> >
> >
> > Ulisses
> >
> >
> > Debian GNU/Linux: a dream come true
> > -----------------------------------------------------------------------------
> > "Computers are useless. They can only give answers." Pablo Picasso
> >
> > ---> Visita para saber acerca de la <---
> > ---> Asociaci髇 Valenciana de Usuarios de Linux <---
> >
> > ----------------------------------------------------------------------------
> > To unsubscribe, send a message with body containing "unsubscribe tcptrace" to
> > [e-mail].
> >
>

-- 
                Debian GNU/Linux: a dream come true
-----------------------------------------------------------------------------
"Computers are useless. They can only give answers."            Pablo Picasso
--->	Visita  para saber acerca de la	<---
--->	Asociaci髇 Valenciana de Usuarios de Linux		<---
 
----------------------------------------------------------------------------
To unsubscribe, send a message with body containing "unsubscribe tcptrace" to
[e-mail].