[OpenSIPS-Users] Record-Route and Dialog topology_hiding()

[Newlin, Ben]

I understand that normally you would not need RR with TH, but the two concepts are not mutually exclusive in SIP. As I said, I have a need to Record-Route the call on my server as I am advertising a different address than I am listening on. This means that TH will populate the Contact header with the advertised address and if I cannot Record-Route with the actual address then I will not receive sequential requests.


Ben Newlin

From: Bogdan-Andrei Iancu <bogdan at opensips.org>
Date: Wednesday, July 27, 2016 at 3:59 AM
To: OpenSIPS users mailling list <users at lists.opensips.org>, "Newlin, Ben" <Ben.Newlin at inin.com>
Subject: Re: [OpenSIPS-Users] Record-Route and Dialog topology_hiding()

Hi Ben,

As I mentioned in different thread, TH is not compatible with the RR mechanism. If you do TH, your OpenSIPS will act as and end point (from SIP perspective), so there will be no Route/RR headers at all. So no need to do loose_route or so. You just do TH matching for the sequential requests and nothing more.

Regards,


Bogdan-Andrei Iancu

OpenSIPS Founder and Developer

http://www.opensips-solutions.com
On 22.07.2016 16:48, Newlin, Ben wrote:
Hi,

I am using the Dialog module with topology_hiding() in my server and I have a need to Record-Route the call on my server as I am advertising a different address than I am listening on. I have found what I believe is an inconsistency in the handling of Record-Route within the Dialog topology_hiding functionality. The topology_hiding isn’t a true B2BUA, but it does set up different parameters for the incoming UAC and outgoing UAS sides of the call for the Via headers, Record-Route and Route headers, and the Contact header(s).

The problem is that the record_route() and loose_route() functions operate on different sides of the call. The record_route() function will only add a Record-Route header to the outgoing UAS side of the call. And since the record_route() function cannot be called from onreply_route, but is no way to add a Record-Route header to the UAC side of the call.

On the other hand, the loose_route() function only operates on the incoming UAC side of the call and there is no way to perform loose_route() on the UAS side of the call.

So there is a situation where Record-Route headers can only be added on the outgoing UAS side, but the associated Route headers can only be removed on the incoming UAC side (where they won’t exist since they can’t be added) and any added headers on the UAS side cannot be processed properly due to the lack of loose_route.

I can provide further information if this is unclear. It should be easily reproducible by attempting to use record_route in a topology_hiding scenario. The route is added to the outbound leg, but is not removed by loose_route so the message is looped back every time.

Ben Newlin | Sr Voice Network Engineer, PureCloud
phone & fax +1.317.957.1009 | ben.newlin at inin.com<mailto:ben.newlin at inin.com>
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