Symptom
Call flow:
CUCM -> CUBE -> ITSP
CUBE sends an INVITE with RTP/AVP, and CUBE sends the INVITE out to ITSP with RTP/AVP. ITSP sends an update with SDP within the same transaction and CUBE sends update to CUCM with RTP/SAVP - Crypto SDP towards CUCM. CUCM responds back with 200 ok with RTP/AVP. Now CUBE sends 200 ok against the INVITE with RTP/SAVP - Crypto SDP towards CUCM. CUCM disconnects the call with CC47.
This is seen only with SRTP fallback is used. If i remove SRTP fallback, everything works fine. If SRTP fallback is used, it must not shift of SRTP, if the initial offer from CUCM is RTP. looks like a wrong behaviour.
Conditions
SRTP fallback enabled, initial INVITE comes with RTP
