[SR-Users] Switch from SRTP to RTP when using Zoiper and Bria

[Markus Bönke]

Hello Sergiu,

Thanks for your suggestions. Regarding option b) to put SAVP and AVP, it is not possible with rtpengine at the moment (see https://github.com/sipwise/rtpengine/issues/435 <https://github.com/sipwise/rtpengine/issues/435>). Also using OSRTP does not  work with Zoiper. The only idea to make it compatible which I have is to add an SRTP/RTP option to the server-side subscriber configuration. Depending on this setting I can put either RTP/SAVP or RTP/AVP in the INVITE. The drawback ist that it only works when server and client configuration is matching. 

Thanks and regards

Markus

> Am 19.04.2021 um 14:35 schrieb Sergiu Pojoga <pojogas at gmail.com>:
> 
> Hi Marcus,
> 
> Can't say for Zoiper, but I've worked this case with Counterpath (sadly for Canada - it is no more, has been acquired by Alianza). 
> 
> Anyhow, the final conclusion at the time was: The client is correct to expect that this is the same INVITE request that took different paths to the target (as indicated by the different branch IDs) - and thus correct to reject it with a 482 because the requests are not identical in content. https://tools.ietf.org/html/rfc3261#section-8.2.2.2 <https://tools.ietf.org/html/rfc3261#section-8.2.2.2> states what should occur if there is no To tag
> 
> The suggested solutions were: 
> a) increment CSeq - impossible to do with a proxy
> b) send both SAVP and AVP lines in the SDP of the original INVITE. If media encryption is set to mandatory and SIP TLS is enabled then the SAVP offer would be accepted. If media encryption is off in Bria, then the AVP offer would be accepted
> 
> Good luck.
> 
> On Mon, Apr 19, 2021 at 3:55 AM Markus Bönke <mb at tenios.de <mailto:mb at tenios.de>> wrote:
> Hello NG,
> 
> I saw the following threads discussing how to switch to RTP when a client does not support SRTP. 
> 
> https://lists.kamailio.org/pipermail/sr-users/2018-May/101341.html <https://lists.kamailio.org/pipermail/sr-users/2018-May/101341.html>
> https://lists.kamailio.org/pipermail/sr-users/2016-September/094457.html <https://lists.kamailio.org/pipermail/sr-users/2016-September/094457.html>
> 
> There are some issues with Zoiper and Bria which also persist in the latest versions. Has anyone got it work with Zoiper and Bria? 
> 
> Thanks and regards
> 
> Markus
> 
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