[OpenSIPS-Users] rtpproxy - preserve original session after rejected reinvite

[Jeff Pyle]

List,

I was never able to truly solve this issue.  Instead I worked around it by
preventing the ports from changing between the G711 and the T38 sessions.
 Well, now I've encountered situations I can't control.  I need to ask
again if anyone has any thoughts on how to handle a refused re-invite in
rtpproxy when the proposed session was going to use different RTP port
numbers than the existing one.

All the details are in the thread.

Thanks in advance for any suggestions.


- Jeff



On Thu, Feb 6, 2014 at 7:57 PM, Jeff Pyle <jpyle at fidelityvoice.com> wrote:

> Just for grins I tried the engage_rtp_proxy() approach instead.  It has
> the same problem, using the newly indicated ports on the old session.  This
> sounds like a bug to me.
>
>
> - Jeff
>
>
> On Tue, Feb 4, 2014 at 10:06 AM, Jeff Pyle <jpyle at fidelityvoice.com>
> wrote:
>
>> Hello,
>>
>> This is on Opensips 1.10 and rtpproxy 1.2.1.  I have them dual-homed on
>> public and private networks with rtpproxy in bridge mode.  Overall, things
>> work well.  I've recently encountered a problem I don't know how to solve
>> relating to a T.38 reinvite that is rejected by the public side.  rtpproxy
>> uses the new ports in the T.38 SDP even though it was rejected, effectively
>> killing the G.711 session that should be maintained.
>>
>> Here's a specific call flow.  A call comes in from the public side and is
>> routed to the private side, having rtpproxy_offer run on it.  The private
>> UA 10.1.30.219 answers the G.711 call with this SDP in its 200 OK:
>>
>> v=0.
>> o=userX 198 2 IN IP4 10.1.30.219.
>>  s=-.
>> c=IN IP4 10.1.30.219.
>> t=0 0.
>> m=audio *50460* RTP/AVP 0.
>> a=ptime:20.
>> a=rtpmap:0 PCMU/8000.
>>
>>
>> rtpproxy_answer happens on this; the call establishes with two-way RTP
>> and all is well.  A few moments later the private UA re-invites to T.38
>> with this SDP:
>>
>> v=0.
>> o=userX 198 3 IN IP4 10.1.30.219.
>>  s=-.
>> c=IN IP4 10.1.30.219.
>> t=0 0.
>> m=image *50462* udptl t38.
>> a=T38FaxVersion:0.
>> a=T38MaxBitRate:14400.
>> a=T38FaxRateManagement:transferredTCF.
>> a=T38FaxMaxBuffer:262.
>> a=T38FaxMaxDatagram:176.
>> a=T38FaxUdpEC:t38UDPRedundancy.
>>
>>
>> You'll notice the UA has changed its port from 50460 to 50462.
>>  rtpproxy_offer("frocl") is called on this re-INVITE and rtpproxy redirects
>> the inbound RTP to 10.1.30.219:*50462*.
>>
>> A few milliseconds later a 488 comes in from the public side.  We're left
>> with our original G.711 session, which is fine, but the RTP is now going to
>> 50462 instead of 50460 and the UA doesn't see it.
>>
>> I'm struggling with an rtpproxy_offer/rtpproxy_answer configuration to
>> allow the session to revert in the event the re-invite is rejected like
>> this.  I've tried rtpproxy_offer without the "l" lookup flag - no effect.
>>  Any thoughts?
>>
>> Another detail... I use rtpproxy_offer/rtpproxy_answer to manage mixed
>> early and late negotiation scenarios that engage_rtp_proxy() cannot handle.
>>  The automatic function isn't an option unfortunately.
>>
>>
>> - Jeff
>>
>>
>
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