SDP c= and RTP
One-way audio
The ladder can be perfect while one RTP direction never arrives.
- INVITE — Delayed offer from CUCM.
- INVITE + SDP — CUBE offers early to the provider.
- 200 + SDP — The carrier's answer has a connection address.
- 200 — The 200 toward CUCM has no SDP. CUCM has no address to send RTP to.
Open both legs before you restart CallManager. A CSS miss does not connect a call and then drop one direction. QoS can still hurt a call that has two RTP streams. It does not explain a missing answer.