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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
NOTE Meet-me bridges do not offer any security, scheduling, or name-confirmation
features. Security and scheduling features are offered by the Cisco MeetingPlace and
Cisco MeetingPlace Express products. The conference controller could be given access
to the ConfList softkey, which will allow the controller to view the conference participants
by caller ID information. The conference controller can individually remove users,
but the conference controller does not have access to the users’ line state information.
Cisco MeetingPlace and MeetingPlace Express allow the conference controller to see
which conference participant has a phone on hold. This is especially useful if MoH
is being injected into the conference bridge. If the bridge has not been set up by the
controller, callers to the meet-me number pattern receive a reorder tone.
Music on Hold 389
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:
■ 16-bit PCM WAV file
■ Stereo or mono
■ 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.
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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
239.1.1.1 through 239.255.255.254 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.
Music on Hold 391
Figure 15-12 Music on Hold: Resource Selection
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
IP Phone B
User Hold Audio 2
MOH Server B
Phone B
Puts
Phone A
on Hold
Listen to Audio 2
Use MOH Server A
Server
MOH B
Audio 1
Audio 2
Audio 3
Audio 4
IP Phone A
User Hold Audio 4
MOH Server A
Server
MOH A
Audio 1
Audio 2
Audio 3
Audio 4
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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) × (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 (http://www.cisco.com/go/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
Music on Hold 393
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
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.
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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
Music on Hold 395
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)
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
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.
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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.
Check the Allow Multicasting check box for each MoH audio source. This applies to MoH
audio sources and to fixed MoH audio sources.