[SR-Users] [rtpengine] No media from WebRTC UA

Richard Fuchs rfuchs at sipwise.com
Tue May 20 14:15:17 CEST 2014

On 05/16/14 20:30, Alexey Rybalko wrote:

> During the call from Fire I saw a lot of "SRTP output wanted, but no
> crypto suite was negotiated" messages  from rtpengine. However DTLS is
> finally was established. Is that one more issue of Firefox?

Some DTLS-SRTP endpoints seem to be slow with starting or accepting the
DTLS handshake. What I've seen in my tests was that some "active"
endpoints have a delay of a few seconds before they start the DTLS
handshake, while some "passive" endpoints only start accepting the DTLS
handshake after they've received the signalling answer (while the RFC
requires them to accept DTLS right away after sending the offer).

Both of these cases somewhat eliminate one of the advantages that
DTLS-SRTP has over SDES: it still breaks early media. If your RTP side
sends media before the SRTP side has finished the DTLS handshake, you
will lose packets and see those messages popping up. But I hope that
these issues will disappear as the code matures.

> Looking in STUN section of the dump files I wonder why Chrome use more
> than 10 binding request (USE-CANDIDATE) for each candidate  while
> Mozilla does it just once.

I've noticed that too and I have no idea why it does that. Doesn't seem
to be causing any problems though.


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