[Tmrg] Test suite: Transfer time vs file size

[Lachlan Andrew]

Greetings,

On 19/04/2008, nfonseca at ic.unicamp.br <nfonseca at ic.unicamp.br> wrote:
>
>  could you please specify what you mean by "application data unit"?

I meant a burst of traffic whose rate is governed by TCP -- I think
that is what the Tmix team mean by the term.  A TCP connection
consists essentially of a sequence of ADUs separated by idle times
when the application has no data to send.

>  I understand that tranfer time per flow is the time elapsed between the
>  arrival of the first bit at the destination and the arrival of the last
>  bit at the destination of a flow (during its lifetime)
>
>  why you consider option 2 meaningless?

It is meaningless for non-greedy flows, because the elapsed time is
often dominated by times when the application has no data to send,
rather than by TCP.

This is like Hamed's example of a chat session.  If a chat session is
a single long-lived TCP connection, then we don't care that we only
get a fraction of a bit per second, as long as each burst that we send
gets sent quickly.

Option 2 makes sense if the flow is *greedy*, so that TCP determines
the total transfer time (that is, the flow consists of a single
application data unit).  In that case options 1 and 2 are identical.

>  Thanks for the clarification and sorry if I am out of phase (you asked for
>  interaction)

Yes, thanks for the interaction.

Cheers,
Lachlan

-- 
Lachlan Andrew  Dept of Computer Science, Caltech
1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA
Ph: +1 (626) 395-8820    Fax: +1 (626) 568-3603
http://netlab.caltech.edu/lachlan