/mcpDescription Restriction A Cisco Unified Communications Manager cluster or system supports only virtualized deployments on Cisco Unified Computing System (UCS) servers or other Cisco-approved third-party server configurations. You cannot use the Music On Hold feature with an external source (USB audio dongle) for the nodes that provide MOH from an external source. Cisco Unified Communications Manager System Support The administrator can designate a Music On Hold server as either unicast or multicast, provided that resources exist to support multicast. Multicast Support Caller-specific MOH is not supported when calls are received or transferred over QSIG tunneling-enabled SIP trunks. Caller-specific MOH Support The Music On Hold feature does not support the MP3 format. MP3 Format Support Multicast MOH does not support interoperability between H.323 and SIP protocols. Interoperability between H.323 and SIP Protocols Multicast MoH audio streams are not encrypted and do not support SRTP. SRTP Support MTPs do not support multicast streams. Multicast Streams Cisco Unified Communications Manager does not support encryption of multicast Music On Hold RTP streams. For secure MOH audio, you should not configure multicast audio sources. Encryption of Multicast Music On Hold RTP Streams The fixed Music On Hold device cannot specify an audio source that connects through a USB, because Cisco Unified Communications Manager does not support USB when running on VMware. However, VMware supports internal Music On Hold. Fixed Music On Hold Device Cisco Unified Communications Manager takes no action when a Music On Hold server fails during an active Music On Hold session. MOH Server Failure When an MTP resource gets invoked in a call leg at a site that is using multicast MOH, Cisco Unified Communications Manager falls back to unicast MOH instead of multicast MOH. Multicast MOH If you do not provision the user and network MOH audio source identifiers, or if one or both values are invalid, the caller-specific MOH information in the SIP header is ignored. The call reverts to tone on hold and an invalid MOH audio source alarm is raised. Provisioning • When both the user and network MOH audio source identifiers are present in the header, any invalid value is replaced by the default value (0). • If both values are zero, or the only value is zero, the header in the incoming INVITE is ignored. Header Values Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs 631 Custom Features Music On Hold Restrictions