[SR-Users] Add Record-Route on 200 OK

[Daniel-Constantin Mierla]

Hello,

just to complete a bit about Via vs Record-Route: the reply received by
Kamailio will have only the addresses of the hops from Kamailio to the
sender of the request (caller). But if there are hops between Kamailio
and callee, those addresses are no longer in Via headers. Via is used to
route reply back to the caller and needs to be the addresses from
current hop towards the caller.

So even if you try to use Via addresses to rebuild the Record-Route that
is not going to work.

Also, in many cases, Record-Route headers carry special URI parameters
that are very important for the node that added Record-Route (like
dialog ids, masks for From/To updates, etc).

Therefore you should not add a record-route for a node in the path of
signaling that you don't control and you don't know what expects to be
there.

The right fix is in UA side to properly mirror Record-Route headers.

Cheers,
Daniel

On 06/01/16 16:48, Igor Potjevlesch wrote:
> Hi Alex,
>
> You're right, it was my mistake. It's one of the UA in the call-flow which
> not put the Record-Route into the replies.
> So, the issue is not on Kamalio.
>
> Nevertheless, the UA put the Record-Route into Via headers. Is there a
> simple way to copy the Via into Record-route headers?
>
> Regards,
>
> Igor.
>
>
> -----Message d'origine-----
> De : sr-users [mailto:sr-users-bounces at lists.sip-router.org] De la part de
> Alex Balashov
> Envoyé : mercredi 6 janvier 2016 16:42
> À : Igor Potjevlesch <sr-users at lists.sip-router.org>
> Objet : Re: [SR-Users] Add Record-Route on 200 OK
>
> Kamailio has no hand in this behaviour. It appends the Record-Route header
> to the initial invite, but dealing with it from that point onward, including
> ensuring that it is copied into replies sent back to the initiator, is
> entirely the responsibility of the user agents/endpoints, not the proxy.
>
> --
> Alex Balashov | Principal | Evariste Systems LLC
> 303 Perimeter Center North, Suite 300
> Atlanta, GA 30346
> United States
>
> Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
> Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
>
> Sent from my BlackBerry.
>   Original Message
> From: Igor Potjevlesch
> Sent: Wednesday, January 6, 2016 10:30
> To: 'Kamailio (SER) - Users Mailing List'
> Reply To: Kamailio (SER) - Users Mailing List
> Subject: Re: [SR-Users] Add Record-Route on 200 OK
>
> Hi Alex,
>
> It what I was thinking. What could cause this into Kamailio?
>
> Regards,
>
> Igor.
>
> -----Message d'origine-----
> De : sr-users [mailto:sr-users-bounces at lists.sip-router.org] De la part de
> Alex Balashov Envoyé : mercredi 6 janvier 2016 15:39 À :
> sr-users at lists.sip-router.org Objet : Re: [SR-Users] Add Record-Route on 200
> OK
>
> Igor,
>
> No, that is not normal. The UAS (the server receiving the initial
> INVITE) is required to copy the Record-Route into dialog-forming responses.
>
> From RFC 3261 Section 12.1.1 ("UAS Behavior"):
>
> When a UAS responds to a request with a response that establishes a dialog
> (such as a 2xx to INVITE), the UAS MUST copy all Record-Route header field
> values from the request into the response (including the URIs, URI
> parameters, and any Record-Route header field parameters, whether they are
> known or unknown to the UAS) and MUST maintain the order of those values.
>
> -- Alex
>
> --
> Alex Balashov | Principal | Evariste Systems LLC
> 303 Perimeter Center North, Suite 300
> Atlanta, GA 30346
> United States
>
> Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
> Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
>
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-- 
Daniel-Constantin Mierla
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
Book: SIP Routing With Kamailio - http://www.asipto.com
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