[sr-dev] double record-routing also at outbound edge

[Olle E. Johansson]

This was discussed briefly at a SIPit a few years ago. Outbound seems to 
focus on session setup, not session management. What happens
if a connection goes down and a device re-registers with a new
reg-id during a call?

I think you two have hit a very good issue with outbound that needs
to be discussed.

/O


28 apr 2013 kl. 21:37 skrev "Peter Dunkley" <peter.dunkley at crocodile-rcs.com>:

> Hi Juha,
> 
> This sounds like a bug with the outbound specification.  I can't believe
> that the ability to re-target dialogs would be deliberately removed by the
> outbound enhancement without it being mentioned in the RFC.
> 
> Perhaps the right thing to do would be to raise this issue on the
> appropriate IETF mailing lists and seeing if the designers of the
> specification have an opinion rather than just using a proprietary
> solution like contact aliasing?
> 
> Regards,
> 
> Peter
> 
>> i have one more comment on flow token vs. contact aliasing.
>> 
>> flow token is part of a route uri that represent a proxy in the route
>> set.  route set cannot be changed during the dialog, but remote target
>> uri can.  from rfc3261:
>> 
>>   Requests within a dialog MAY contain Record-Route and Contact header
>>   fields.  However, these requests do not cause the dialog's route set
>>   to be modified, although they may modify the remote target URI.
>>   Specifically, requests that are not target refresh requests do not
>>   modify the dialog's remote target URI, and requests that are target
>>   refresh requests do.  For dialogs that have been established with an
>>   INVITE, the only target refresh request defined is re-INVITE (see
>>   Section 14).  Other extensions may define different target refresh
>>   requests for dialogs established in other ways.
>> 
>>      Note that an ACK is NOT a target refresh request.
>> 
>>   Target refresh requests only update the dialog's remote target URI,
>>   and not the route set formed from the Record-Route.
>> 
>> if flow token is used instead of contact aliasing to store the remote
>> target uri, then it is not possible to modify the remote target uri via
>> target refresh requests (e.g. when moving from wifi to mobile network)
>> and such setup is violating the above text of rfc3261.
>> 
>> this problem does not exist with contact aliasing, because
>> add_contact_alias() is called on each in-dialog target refresh request,
>> which allows changing of remote target uri during the dialog.
>> 
>> -- juha
>> 
>> _______________________________________________
>> sr-dev mailing list
>> sr-dev at lists.sip-router.org
>> http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-dev
>> 
> 
> 
> -- 
> Peter Dunkley
> Technical Director
> Crocodile RCS Ltd
> 
> 
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