Currently, if one Cisco VCS node in a clustered deployment fails or loses network connectivity for any reason, or if the Unified CM restarts, all active
calls going through the affected node will fail. The calls are not handed over to another cluster peer. This is not new behavior
in X12.5.x, but due to an oversight it was not documented in previous releases. Bug ID CSCtr39974 refers.
Cisco VCS does not terminate DTLS. We do not support DTLS for securing media and SRTP is used to secure calls. Attempts to make DTLS
calls through Cisco VCS will fail. The DTLS protocol is inserted in the SDP but only for traversing the encrypted iX protocol.
From X12.5, Expressway provides limited SIP UPDATE support over MRA connections for session refresh purposes only, as specified
by RFC 4028. However, you should not switch this on unless you have a specific requirement to use this capability. Any other use of SIP
UPDATE is not supported and features that rely on this method will not work as expected.
Cisco VCS does not support the SIP UPDATE method (RFC 3311), and features that rely on this method will not work as expected.
Audio calls may be licensed as video calls in some circumstances. Calls that are strictly audio-ONLY consume fewer licenses
than video calls. However, when audio calls include non-audio channels, such as the iX channel that enables ActiveControl,
they are treated as video calls for licensing purposes.