I have an upstream carrier who has a=rtcp:12301 IN IP4 CARRIER_IP in the media attribute of SIP INVITE, how can SEMS filter it the SDP it stop passing-thru to the Downstream carrier? This reason being, in Leg B, We have c=IN IP4 SEMS_IP and a=rtcp:12301 IN IP4 CARRIER_IP causing some sort of IP mismatch and call being dropped at the downstream end. Hence, I was wondering, what would be the best way to tackle this issue?
Hi Rabani
Looking at the INVITE you shared, It doesn’t seem like the rtcp a-line is the issue. This a-line simply specify rtcp details and has nothing in common to the c-line.
What SIP Rejection Code are you getting from Downstream?
In your INVITE the upstream is also trying to initiate a receive-only video call. Have you tried disabling the video to see if the audio call goes fine?
@EAfang We are not able to control the Upstream INVITE from the Carrier, hence, I was looking forward to a way to filter those attributes using SEMS and send a filtered INVITE to the downstream.
and the issue with the Downstream is that in the leg b INVITE (SEM->DownStream), it has a=rtcp:12301 IN IP4 UPSTREAM_CARRIER_IP instead of a=rtcp:12301 IN IP4 SEMS_IP, therefore, it is causing a mismatch which is forcing the DownStream to drop the call
The issue I’m trying to solve is the leg b not leg a
Leg B is
Bypassing LB doesn’t help either as SEMS is still carrying forward the Upstream carrier IP in its media attribute which it should as SEMS should doing Topology hiding. Maybe @dmitry.s Can help us understand better as to why SEMS isn’t hiding/removing upstream Carrier IP in leg b media attributes of the INVITE (SEM → CUSTOMER): a=rtcp:12301 IN IP4 UPSTREAM_CARRIER_IP instead of a=rtcp:12301 IN IP4 SEMS_IP