Re: [Sip] Info regarding Preloaded Route Set

[Christer Holmberg <christer.holmberg@lmf.ericsson.se>]

Hi,

> I have a doubt in using Pre-Loaded Route Set at UA end.
>
> Let us say UA1 has a Pre-Loaded Route Set of  PR1, PR2, PR3.  (all routers
> are strict routers)
>
> UA1 initiates a call to UA2.
>
> The INVITE looks like
>           INVITE: PR1
>           Route:    PR2, PR3, UA2
>
> Now PR1 doesn't Record-Route.
>           UA2 sends the RPR (182) response to UA1
>
>           with Record-Route as   PR3, PR2
>
> On receiving the Record-Route set,  UA1 updates its local Route-Set.
> Now its Route Set contains  PR2, PR3 only.  Hence successive requests
> directly reaches PR2.
>
> Now if UA1 want to terminate the call by sending CANCEL,
>
>      As per the latest Route Set present at UA1,  CANCEL should go to PR2
> directly.
>      It looks like
>           CANCEL:  PR2
>           Route:    PR3, UA2contact

[CHH] I don't think so. The CANCEL shall be routed like the INVITE.

> This scenario leads to two questions:
>
>      1   Is it valid to update the local Route Set at UA1 on receiving the
> Record-Route header in RPR (not final response)
>           and use it for subsequent Requests related to Dialog.

[CHH] Yes. You may need it for requests (PRACK, UPDATE, INFO...) before you
have received the final response for the INVITE.

>      2.  If YES: where should CANCEL go.   As per RFC 3261, CANCEL should
> look like its original INVITE.
>           But in this case, both Request URI and Route header got modified.
> Is it valid??

[CHH] The CANCEL goes wherever the INVITE went, using the same route.

Regards,

Christer Holmberg
Ericsson Finland


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