From: Liangping Ma (lma@mail.eecis.udel.edu)
Date: 02/26/04
Date: Thu, 26 Feb 2004 20:39:05 -0500 (EST) From: Liangping Ma <lma@mail.eecis.udel.edu> Subject: RE: tcptrace Regarding RTO value of Linux TCP Message-ID: <Pine.GSO.4.58.0402262029030.25888@frink.ece.udel.edu>
Hi, all,
I do not quite agree with several of the preceeding messages.
I think RTOs are constant to some extent in current TCP
implementations. True, the RTTs are dynamic, so are the RTOs.
But in reality (see RFC 2988, http://www.faqs.org/rfcs/rfc2988.html), the
computed RTOs are compared to a so-called minimum RTO. If the RTOs are
less than the minimum RTO, then they are rounded to that minimum RTO.
For example, if the computed RTOs are all less than 1 second, and if the
minimum RTO is set to 1 second, then the RTOs, after this processing, will
be all equal to 1 second.
Liangping
On Thu, 26 Feb 2004, Ruhai Wang wrote:
> Juan:
>
> Thanks for the response. You did answer my question.
>
> I believe your understanding is correct.
>
> The question originally came from a discussion about
> packets retransmissions. Please see the attached pdf
> file which contains two TSG and one RTT plots. The
> second TSG plot is the enlarged view of a
> retransmission scenario in which four consecutive
> packets are retransmitted as you can observe clearly.
> The RTT is for the transmission which has two
> retransmission scenarios occurred. The transmission
> was done using Linux 7.4 TCP SACK over a CLEAN channel
> (BER=0) with RTT around 270 ms in a lab. It appears
> the retransmissions are caused by retransmission timer
> out rather than bit error corruption since no bit
> error is introduced to the channel. What do you think?
>
>
> Wang
>
> --- Juan Francisco Torreblanca
> <juan.torreblanca@tartec.com> wrote:
> > RTO changes dynamically based on every measured RTT.
> > As far as I know, RTO doesn't have a known value for
> > any TCP implementation, are you referring to this or
> > am I missing something?
> >
> > Rgds,
> > Juan Torreblanca.
> >
> > -----Original Message-----
> > From: Ruhai Wang [mailto:wangnewton2000@yahoo.com]
> > Sent: sábado, 21 de febrero de 2004 21:50
> > To: tcptrace@tcptrace.org
> > Subject: tcptrace Regarding RTO value of Linux TCP
> >
> > Does anyone know the specified value of
> > Retransmission
> > Time Out(RTO) for Red Hat Linux 7.4 TCP?
> >
> > Thanks!
> >
> > Wang
> >
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