Yes, you are right, in general, proxy should not modify but RFC 4028,
defined the header, it is allowed to define the semantics of the header.

I would still not do the optimization so that UAC gets a chance to see
whether the Session-Expires is acceptable to it.

Thanks,
Neel


> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:sip-implementors-
> [EMAIL PROTECTED] On Behalf Of venkatesh chandran
> Sent: Monday, April 23, 2007 7:14 AM
> To: [EMAIL PROTECTED]
> Cc: [email protected]
> Subject: Re: [Sip-implementors] Regarding SESSION-TIMER
> 
> Hello Neel,
> For the query2(what is the real use behind the 422 response?) as you
> specified i proposed an optimisation.
> But it is not violated RFC 4028.In the section-8.1, it is specified that
> proxy can modify the session-expires header.
> 
> Pls provide suggesstions whether the optimisation is possible?
> 
> Best Regards,
> Venkatesh
> 
> 
> 
> On 4/23/07, Bala Neelakantan <[EMAIL PROTECTED]> wrote:
> >
> > Responses inline.
> >
> > Thanks,
> > Neel
> >
> >
> > > -----Original Message-----
> > > From: [EMAIL PROTECTED] [mailto:sip-
> implementors-
> > > [EMAIL PROTECTED] On Behalf Of venkatesh chandran
> > > Sent: Saturday, April 21, 2007 5:56 AM
> > > To: [email protected]
> > > Subject: Re: [Sip-implementors] Regarding SESSION-TIMER
> > >
> > > Hello *,
> > > Thanks for the information.
> > >
> > > I have some more queries,
> > > 1)When INVITE send from UAC with the session-expires value less than
> the
> > > Min-SE configured in the proxy, the proxy will reject the INVITE with
> > 422
> > > response and include the Min-SE header.After that UAC will send a new
> > > INVITE
> > > with session-expires and Min-SE returned in the 422 response.
> > > Now when RE-INVITE send with session-expires less than Min-SE then
> what
> > > will
> > > be the behaivour of the proxy?Again 422 will be send by proxy?
> > >
> >
> > Yes, the situation you describe can happen, if there are multiple
> proxies
> > and each of them have a progressively increasing Session-Expires and
> > Min-SE.
> > In this scenario, it is possible that the 422's can be generated till it
> > the
> > value of Session-Expires and Min-SE are acceptable to all the
> intermediate
> > proxies.
> >
> > > 2)what is the real use behind the 422 response?
> > > when INVITE is received with session-expires less than the min-se
> > > configured
> > > in proxy then the proxy can modify the session-expires to the min-se
> > > configured value and forward the INVITE to terminating side and in the
> > 200
> > > OK response the UAC will be indicated with the new session-expires and
> > if
> > > parameter refresher=uac, then uac can refresh the session considering
> > the
> > > new session-expires.Whether this is possible?
> > > If this is applicable a INVITE may not rejected.
> >
> > A Proxy can not modify the SIP headers.  It can only add headers.  So,
> > what
> > you describe is an optimization, but it is violation of the RFC 3261.
> >
> > >
> > > Pls give your points.
> > >
> > > Best Regards,
> > > Venkatesh
> > >
> > >
> > > On 4/20/07, Manjunath Warad <[EMAIL PROTECTED]> wrote:
> > > >
> > > > Please see inline...
> > > >
> > > >
> > > >
> > >
> >
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> > > >
> > > >    -----Original Message-----
> > > >    From: [EMAIL PROTECTED]
> > > >    [mailto: [EMAIL PROTECTED] On Behalf
> > > >    Of venkatesh chandran
> > > >    Sent: Friday, April 20, 2007 4:53 PM
> > > >    To: [email protected]
> > > >    Subject: [Sip-implementors] Regarding SESSION-TIMER
> > > >
> > > >    Hello All,
> > > >    I have the following queries regarding the SESSION-TIMER
> handling.
> > > >
> > > >    -When UAC and UAS are not supporting the SESSION-TIMER,then
> > > >    what will be the behaviour of call-stateful proxy?
> > > >    -Will call-stateful proxy still sends the SESSION-TIMER
> > > >    header in the INVITE that is forwarded to the terminating
> > > >    side with the value configured locally and handles the
> > > >    session-timer?
> > > >    -After SESSION-TIMER has expired the session and dialog
> > > >    details will be deleted in call-stateful proxy and BYE will
> > > >    not be triggered to UAC and UAS.Now how the UA's are
> > > >    informed about the release of the call?
> > > >
> > > > Session Timers in proxies are triggered and regulated (in most
> cases)
> > > from
> > > > UA. I mean to say, if UA's support then only proxy session timer
> will
> > be
> > > > activated.
> > > >
> > > >    Kind Regards,
> > > >    Venkatesh
> > > >    _______________________________________________
> > > >    Sip-implementors mailing list
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> > > >
> > > >
> > > >
> > > >
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> >
> >
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