[asterisk-dev] T1 sip 500ms or 1s ?

[Eduardo Nunes Pereira]

I thing about this session 17.1.2.2 is not a INVITE is a REGISTER

On Thu, Jun 18, 2009 at 1:17 PM, Kristian Kielhofner <
kristian.kielhofner at gmail.com> wrote:

> On Thu, Jun 18, 2009 at 12:03 PM, Mark Michelson <mmichelson at digium.com>
> wrote:
> >
> > David Hansen wrote:
> > > Are your PBX and phone on same subnet?  Is the phone SIP capable and
> listening on port 5060?  You mention T1, but this has no relationship to SIP
> convos.
> > >
> > > David Hansen
> >
> > In SIP, there is a timer called T1 used as a base for calculating
> retransmission
> > times.
> >
> > In answer to the originally-posted question, the SIP T1 timer defaults to
> 500
> > ms. Looking at the code in sip_reliable_xmit, we set a value called
> siptimer_a
> > to be 2 * pkt->timer_t1. This value is what is passed to the scheduler
> for the
> > retransmission time.
> >
> > Reading RFC 3261, section 17.1.1.2:
> >
> >   "If an unreliable transport is being
> >    used, the client transaction MUST start timer A with a value of T1.
> >    If a reliable transport is being used, the client transaction SHOULD
> >    NOT start timer A (Timer A controls request retransmissions).  For
> >    any transport, the client transaction MUST start timer B with a value
> >    of 64*T1 seconds (Timer B controls transaction timeouts).
> >
> >    When timer A fires, the client transaction MUST retransmit the
> >    request by passing it to the transport layer, and MUST reset the
> >    timer with a value of 2*T1."
> >
> > So it appears that this may be an instance where we are doing things a
> bit
> > out-of-spec here. I wonder if there was some sort of justification for
> this when
> > it was written...
> >
> > Mark Michelson
> >
>
> IIRC the T1 value is calculated based off of whatever qualify returns
> (if enabled).  I don't remember what happens if you have qualify
> disabled...
>
> This may have changed in recent versions but I remember it being
> correct at some point in time.
>
> --
> Kristian Kielhofner
> http://www.astlinux.org
> http://blog.krisk.org
> http://www.star2star.com
> http://www.submityoursip.com
> http://www.voalte.com
>
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-- 
Eduardo Nunes Pereira
Consultor de Informática e Internet
cel.: (48) 9989-2997
email: eduardonunesp at gmail.com
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