Constraints

Multi-system Selective SRTP Pass-through support has the following constraints:

1. The realm, or realms in which the calling and called parties are located are configured for Multi-system Selective SRTP Pass-through support.
2. The call session does not require SIP—INFO to RFC 2833 tone translation.
3. The call session does not require SDES and can be used for the exchange of SRTP keying material. Both the calling and called parties must support the same key exchange protocol.
4. Multi-system Selective SRTP Pass-through support should not be enabled in topologies where core-side application servers may change the c-line to inject a media server or some other media device in the media path. In such cases, SRTP should be terminated at the SD for each endpoint, so that the media server receives unencrypted media. In the other case, where the c-line is not subject to modification, Multi-system Selective SRTP Pass-through can be enabled.

   If any of these conditions are not met, Multi-system Selective SRTP Pass-through processing cannot be provided, and the call is serviced as specified by SRTP Media Proxy Mode.