[Freeswitch-users] SRTP in PhonerLite and Freeswitch

Krzysiek cris7 at o2.pl
Wed Apr 23 12:01:13 PDT 2008

I have 2 softphones PhonerLite (they support SRTP via SDES ) and the freeswitch (windows RC1 version) server and I wanted to make secure call between those two endpoints (SRTP).
I spend whole day on testing this scenario and my conclusions are:
- when the option: <action application="export" data="sip_secure_media=true"/> is uncommented, and both enpoints have enabled SRTP then:
1) Initiator of the session sends SIP Invite with a=crypto paramter and supported codecs
2) Freeswitch receives SIP Invite and sends SIP Invite to the receiver (also with the crypto)
3) Receiver receives the SIP Invite with the a=crypto parameter and he sends back supported codecs with 200 OK message (but without a=crypto parametr. Is that ok? I'm afraid not)
4) Freeswitch sends 200 OK message but witout any codecs: m=audio 0 RTP/AVP 19 and no a= parameters!
5) Final result is that the second leg of the session between Freeswitch and receiver has SRTP transport enbaled and the first leg (initiator- Freeswitch) doesn't hear anything - no codecs! However Freeswitch is sending RTP (not SRTP) pacekets to the initiator.

Could someone explain to me, what is going on, and why freeswitch doesn't forward codecs accepted by the receiver to the initiator?
Is it a PhonerLite's bug or freeswitch's? Maybe someone has tested SRTP with the PhonerLite softphone or any other free softphone with srtp support?

When I uncommented: <param name="Inbound-no-media" value="true">
everything works fine. The parameter <action application="export" data="sip_secure_media=true"/> doesn't change anything then (but i cound miss something).

Thanks for help
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