SRTP Session Agent counters are available from apSecuritySASRTPStats. The OID prefix is 1.3.6.1.4.1.9148.3.9.5.3 which is found in the ap-security.mib file.

The apSecuritySASRTPStats contains numerous session agent statistics concerning SRTP traffic and corresponds to the show sa stats srtp command and sa-srtp HDR group.