Music on Hold

CUCM may be configured to provide MoH. The MoH feature has two main requirements:

■ An MoH server must provide the MoH audio stream sources.

■ CUCM must be configured to use the MoH streams provided by the MoH server when a call is placed on hold.

The integrated MoH feature enables users to place on-net and off-net callers on hold with music instead of the default "one on hold." The MoH source makes music available to any on-net or off-net device placed on hold. On-net devices include Cisco IP Phones and applications placed on hold. Off-net users include those connected through MGCP, SIP, and H.323 gateways. The MoH feature is also available for plain old telephony service (POTS) phones connected to the Cisco IP network through Foreign Exchange Station (FXS) ports.

It is also possible to configure multicast MoH streaming to leverage external media servers providing media streams. CUCM Express and Cisco Unified Survivable Remote Site

Telephony (SRST) gateways can be configured as media streaming servers for MoH, too. The CUCME and SRST router-based resources provide MoH by streaming one audio file stored in the router's flash memory or a fixed audio source connected through an optional E&M (ear and mouth) hardware interface. You can find detailed information about this feature in the CUCM Solution Reference Network Design (SRND) Guide.

The CUCM integrated MoH Server supports multicast and unicast for MoH streaming. The advantage of using multicast for MoH streaming over unicast is to save bandwidth and to reduce load on the MoH server. Saving bandwidth is normally not a major issue for campus LAN environments, but reducing load on the MoH server is always a big consideration. Reducing the number of media streams is especially advantageous when the MoH server is co-located on the same server as call processing. It is advisable to scope MoH traffic to the local site so that MoH does not consume WAN bandwidth. There are various ways of implementing multicast scoping and unicast filtering on the data network.

MoH audio codecs (G.711ulaw, G.711alaw, Cisco wideband, and G.729) are generated by CUCM when files with a .wav extension are uploaded to the MoH server. The recommended format for audio source files includes the following specifications:

■ Sample rates of 48 kHz, 32 kHz, 16 kHz, or 8 kHz

If live audio (Muzak, radio broadcast) is a requirement, MoH can be generated from a fixed source. A sound card is required for a fixed audio source. The fixed audio source is connected to the audio input (line in) of the local sound card. The Cisco MoH USB audio sound card (MUSIC ON HOLD-USB-AUDIO=) must be used for connecting a fixed audio source to the MoH server. This USB sound card is compatible with all MCS platforms supporting CUCM Release 6.x.

This mechanism enables the use of radios, CD players, or any other compatible sound source. The stream from the fixed audio source is transcoded in real time to support the codec that was configured through CUCM Administration. The fixed audio source can be transcoded into G.711 (a-law or mu-law), G.729 Annex A, and wideband, and it is the only audio source that is transcoded in real time.

Before using a fixed audio source to transmit MoH, consider the legalities and the ramifications of rebroadcasting copyrighted audio materials. Consult your legal department for potential issues.

A unicast MoH stream is a point-to-point, one-way audio RTP stream between the server and one endpoint device. Unicast MoH uses a separate source stream for each connection. As more endpoint devices receive MoH, the number of MoH streams increases. If one hundred devices are on hold, there will be 100 independent streams of RTP traffic generated over the network between the server and the endpoints receiving the MoH. The number of streams can potentially have a negative effect on network throughput. Unicast MoH can be useful in networks where multicast is not enabled or where devices are not capable of multicast, thereby still allowing an administrator to take advantage of the MoH feature.

Multicast MoH streams are point-to-multipoint, one-way audio RTP stream between the MoH server and the multicast group IP address. Multicast MoH conserves system resources and bandwidth because it enables multiple users to use the same audio source stream to provide MoH. If 100 devices were simultaneously on hold, a single multicast RTP stream could be replicated over the network to all 100 resources. Bandwidth and server processor utilization would be greatly reduced. It is recommended to use a multicast IP address of through because these multicast addresses are implicitly scoped by the router because the IP packets are generated with a time to live (TTL) value of 2. Each data router decrements the TTL value by 1. When a TTL of 0 is reached, the packet is not forwarded by a router. A TTL of 0 has a drop operation.

The basic operation of MoH in a Cisco Unified Communications environment consists of a holding party and a held party. The holding party is the endpoint placing a call on hold, and the held party is the endpoint placed on hold, receiving MoH.

The MoH stream that an endpoint receives is determined by a combination of the user hold audio source identifier of the device placing the endpoint on hold (holding party) and the configured prioritized list of MoH resources of the endpoint placed on hold (held party). The user hold audio source configured for the holding party determines the audio file that will be streamed when the holding party puts a call on hold, and the held party's list of MoH resources determines the server from which the held party will receive the MoH stream.

Figure 15-12 illustrates an on-net phone being placed on hold by a phone with a different MoH audio source identifier and server configuration. Phone B places Phone A on hold. Phone B will instruct CUCM to place Phone A on hold with Audio Source 2 and the MoH server relevant to Phone B's configuration.

NOTE When multiple MoH servers are active in your network, make sure that all the configured MoH files are available on all MoH servers.

Figure 15-12 Music on Hold: Resource Selection

Server MOH B

Server MOH B

Audio 1 Audio 2 Audio 3 Audio 4

Phone B

Puts Phone A on Hold

Phone B User Hold Audio 2 MOH Server B

Phone B User Hold Audio 2 MOH Server B

Audio I

Audio 2 Audio 3 Audio 4

Audio 1

Listen to Audio 2

Listen to Audio 2

Phone A User Hold Audio 4 MOH Server A

Phone A User Hold Audio 4 MOH Server A

Use MOH Server A

MoH Configuration

Configuration of MoH consists of four main steps. Additional configuration is required if multicast MoH is used.

Step 1 Plan MoH server capacity. Step 2 Configure MoH audio sources:

a. Convert MoH audio files.

b. Configure MoH audio sources. Step 3 Configure the MoH server.

Step 4 Configure MoH service parameters.

Step 5 (Optional) Configure multicast for MoH:

a. Configure audio sources for multicast MoH.

b. Configure the server for multicast MoH.

Capacity planning is crucial to ensure that the hardware can support the anticipated MoH volume of the network. The 7815 and 7825 servers allow up to 250 users to be placed on hold, and the 7835 and 7845 servers allow up to 500 users to be placed on hold (co-resident or standalone). If MoH sessions exceed the platform limitations, various issues can arise:

■ Poor MoH quality

■ Erratic MoH operation

■ Loss of MoH functionality

The following MoH server configuration parameters affect MoH server capacity:

■ Maximum Half Duplex Streams: This parameter determines the number of devices that can be placed on unicast MoH. This value is set to 250 by default. The Maximum Half Duplex Streams parameter should be set to the value derived from the following formula: (Server capacity) - [(Number of multicast MoH sources) x (Number of MoH codecs enabled)]. The value of this parameter should never be set higher than the hardware capacity of the server.

■ Maximum Multicast Connections: This parameter determines the number of devices that can be placed on multicast MoH. The default value is set to 30, which represents a maximum of 30,000. Multicast connections are configured in thousands of held parties because multicast is scalable. The Maximum Multicast Connections parameter should be set to a number that ensures that all devices can be placed on multicast MoH if necessary. Although the MoH server can generate only a finite number of multicast streams (204), a large number of held devices can join each multicast stream through the network multicast protocols. This parameter should be set to a number that is greater than or equal to the number of devices that might be placed on multicast MoH at any given time.

Typically, multicast traffic is accounted for based on the number of streams being generated; however, CUCM maintains a count of the actual number of devices placed on multicast MoH or joined to each multicast MoH stream. This method is different from the way multicast traffic is normally tracked. You can find additional information in the CUCM SRND (

CUCM ships with a default MoH audio file. To add additional MoH audio files, navigate to Media Resources > MoH Audio File Management from CUCM Administration (shown in Figure 15-13). Click the Upload File button, and browse the local directory structure for the WAV audio file.

Figure 15-13 Music on Hold: Audio File Conversion

Figure 15-13 Music on Hold: Audio File Conversion

The uploaded file is automatically converted into four different audio formats. A file status of Translation Complete indicates that the audio file has been successfully converted. If any other status is displayed, or if the status remains open for a long period of time (conversion can take up to several minutes), the audio file translation failed. The uploaded audio file might be in the wrong file format or have improper audio qualities.

Navigate to Media Resources > Music On Hold Audio Source from CUCM Administration to configure the MoH audio sources, as illustrated in Figure 15-14. The MoH audio sources are identified by an MoH audio stream number from 1 to 51. Up to 50 prerecorded sources and 1 live audio source are available per CUCM cluster.

In the Music On Hold Audio Source Configuration window, select the MoH audio stream number of the audio source that you want to configure. Choose the MoH audio source file. The MoH audio source name defaults to the MoH audio source filename, but it can be modified. Enable continuous playing (repeat) of the audio file if desired.

Figure 15-14 Music on Hold: Audio Source Configuration

Figure 15-14 Music on Hold: Audio Source Configuration

If a fixed audio source will be used, navigate to Media Resources > Fixed MoH Audio Source from CUCM Administration to configure a fixed MoH audio source. The source ID is 51 and cannot be modified. The name of the fixed MoH audio source has to be entered, and the fixed MoH audio source must be enabled. Figure 15-15 shows this configuration.

Figure 15-15 Music on Hold: Fixed Audio Source Configuration

Figure 15-15 Music on Hold: Fixed Audio Source Configuration

Navigate to Media Resources > Music On Hold Server from CUCM Administration to configure the MoH server parameters. Figure 15-16 illustrates the default configuration of the MoH media resource. Various parameters can be modified. It is best practice to use a media resource device pool. If MoH functionality is not desired on this server, but other services of the Cisco IPVMS are, the run flag should be set to No. If a fixed audio source that is physically connected to the server is used, the name of the audio source device has to be specified.

Figure 15-16 Music on Hold: Server Configuration

Figure 15-16 Music on Hold: Server Configuration

The following list of CUCM service parameters and the associated defaults are related to MoH:

■ Suppress MoH to Conference Bridge (True)

■ Default Network Hold MoH Audio Source ID (1)

■ Default User Hold MoH Audio Source ID (1)

■ Duplex Streaming Enabled (False)

To enable multicast MoH on an MoH server, the Multicast Audio Source Information section of the MoH server configuration window must be configured. Check the Enable Multicast Audio Sources on This MoH Server check box. The Base Multicast IP Address, Base Multicast Port Number, and Increment Multicast On parameters are automatically populated when you enable multicast MoH on the server. You can modify these values if desired. Figure 15-17 shows this section of the MoH Server Configuration page.

Figure 15-17 Music on Hold: Server Configuration (Multicast Settings)

Figure 15-17 Music on Hold: Server Configuration (Multicast Settings)

NOTE It is recommended to increment multicast on IP address rather than port number to avoid network saturation in firewall situations. This results in each multicast audio source having a unique IP address and helps to avoid network saturation.

All MoH audio sources that have been configured to allow multicasting are listed in the Selected Multicast Audio Sources section of the MoH Server Configuration window. Each audio source can have a different Max Hops value (default is 2). This parameter sets the TTL value in the IP header of the multicast MoH RTP packets to the specified value. The

TTL field in an IP packet indicates the maximum number of routers that an audio source is allowed to cross. If the Max Hops value is set to 1, the multicast MoH RTP packets remain in the subnet of the multicast MoH server.

NOTE When you are using multicast MoH for devices that are not in the same IP subnet, multicast routing has to be enabled in the IP network.

Check the Allow Multicasting check box for each MoH audio source. This applies to MoH audio sources and to fixed MoH audio sources.

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  • arnor
    How to change hold music on cisco phones?
    1 year ago
  • Jensen
    How to change MOH audio source in CUCM?
    1 year ago
  • SVEN
    How to config moh file?
    12 months ago
  • tarja
    How to take hold music off cisco phone?
    4 months ago
  • alan
    How to change cucm moh file?
    2 months ago

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