Subject: RE: [Sipping] Transcoding

From: "Christer Holmberg (JO/LMF)" <[email-masked]>
Date: Fri, 25 Feb 2005 08:22:21 +0100

Hi,

Another solution for inserting the IMS ALG that was presented was to actually forward (instead of sending 305) the INVITE directly to the IMS ALG, eg an intermediate node (in this case the S-CSCF) inserts a Route header in the request, pointing to the IMS ALG, and sends the message there.

Regards,

Christer Holmberg
Ericsson Finland

> -----Original Message-----
> From: David R Oran [mailto:[email-masked]]
> Sent: 24. helmikuuta 2005 18:13
> To: Gonzalo Camarillo (JO/LMF)
> Cc: 'Paul Kyzivat'; Christer Holmberg (JO/LMF); 'sipping'; Medhavi
> Bhatia
> Subject: Re: [Sipping] Transcoding
> 
> 
> 
> On Feb 24, 2005, at 9:35 AM, Gonzalo Camarillo wrote:
> 
> > Hi,
> >
> > before jumping into this type of solution, we have to 
> decide whether 
> > or not we want to treat B2BUAs as proxies. That is, invoke 
> them using 
> > Route header fields, etc... this is something we do not 
> have agreement 
> > on yet...
> >
> Since you have no idea when you route to something with a URI whether 
> you will reach a proxy, a UAS, a redirect server, or a black 
> hole, does 
> this make any practical difference? Saying you can't put the 
> address of 
> a B2BUA into a Route header is unenforceable, and worse, 
> unascertainable except by looking beyond the event horizon of that 
> entity.
> 
> > Thanks,
> >
> > Gonzalo
> >
> > Christer Holmberg (JO/LMF) wrote:
> >> Hi,
> >> A short comment on the re-direction case.
> >>>> or using a re-direction at the callee side.
> >>>
> >>> Problem with that is the redirect needs to somehow 
> specify both the 
> >>> transcoder address and the address of the UAS. How is 
> that going to 
> >>> work?
> >> I think you could use 305. My understanding is that the 
> destination of
> >> the INVITE is still the same as in the INVITE that was 
> re-directed, 
> >> but
> >> the message must traverse via the proxy indicated in the Contact 
> >> header.
> >> The RFC does say that 305 must only be sent by a UAS, 
> though, but I 
> >> see
> >> no reason for that.
> >> Also, 305 has been proposed in 3GPP as one option to 
> re-direct a SIP
> >> message to the IMS ALG node in IMS.
> >> Regards,
> >> Christer Holmberg
> >> Ericsson Finland
> >
> > -- 
> > Gonzalo Camarillo         Phone :  +358  9 299 33 71
> > Oy L M Ericsson Ab        Mobile:  +358 40 702 35 35
> > Telecom R&D               Fax   :  +358  9 299 30 52
> > FIN-02420 Jorvas          Email :  [email-masked]
> > Finland                   http://www.hut.fi/~gonzalo
> >
> David R. Oran
> Cisco Fellow
> Cisco Systems
> 7 Ladyslipper Lane
> Acton, MA 01720 USA
> Tel: +1 978 264 2048
> Email: [email-masked]
> 

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