[SR-Users] rtpengine - SRTP <> RTP missing a=crypto

Matthias Urlichs matthias at urlichs.de
Thu Mar 3 15:45:31 CET 2022

On 03.03.22 14:47, Rhys Hanrahan wrote:
> Yes, from what I’ve seen in the logs there are multiple branches 
> happening. One between Teams and Kamailio and one between Kamailio and 
> Asterisk.
That's just one branch; the incoming call doesn't count. "Real" 
additional branches are created by calling functions like "append_branch".

You should definitely ensure (by adding appropriate logging calls) that 
"rtpengine_manage" is called exactly once per outgoing application/sdp 
message, with all requisite arguments(*). Anything else is a recipe for 
confusion. In my experience that's sufficient(**) to get it all working 
quite nicely.

(*) "trust-address replace-origin replace-session-connection", plus 
either RTP/AVP or RTP/SAVP

(**) unless the opposite end is broken. Right now, for instance, talking 
to Zoom Europe requires a heap of "SDES-no-RANDOM_CRYPTO_ALGORITHM" 
arguments, for both incoming and outgoing calls. Discovering that fix 
was decidedly nontrivial.

-- regards
-- Matthias Urlichs

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