Cisco VGD-1T3, Руководство по настройке программного обеспечения

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Using Cisco Unified Communications Manager to Configure Transcoding and Media Termination Point
Information About Transcoding and MTP for the Cisco VGD 1T3 Voice Gateway
153
Cisco VGD 1T3 Voice Gateway Software Configuration Guide
DSP Farms
A DSP farm is the collection of DSP resources available for transcoding and MTP services. DSP farms
are configured on the voice gateway and managed by Cisco Unified Communications Manager through
Skinny Client Control Protocol (SCCP).
The DSP farm can support a combination of transcoding sessions and MTP sessions simultaneously. The
DSP farm maintains the DSP resource details locally. Cisco Unified Communications Manager requests
transcoding services from the gateway, which either grants or denies these requests, depending on
resource availability. The details of whether DSP resources are used, and which DSP resources are used,
are transparent to Cisco Unified Communications Manager.
The DSP farm uses the DSP resources in network modules on Cisco routers to provide transcoding and
hardware MTP services.
Tip
To determine how many DSP resources your router supports, see the “Allocation of DSP Resources”
section on page 154 .
DSP Farm Profiles
DSP-farm profiles are created to allocate DSP-farm resources. Under the profile you select the service
type (transcode or MTP), associate an application, and specify service-specific parameters such as
codecs and maximum number of sessions. A DSP-farm profile allows you to group DSP resources based
on the service type. Applications associated with the profile, such as SCCP, can use the resources
allocated under the profile. You can configure multiple profiles for the same service, each of which can
register with one Cisco Unified Communications Manager group. The profile ID and service type
uniquely identify a profile, allowing the profile to uniquely map to a Cisco Unified Communications
Manager group that contains a single pool of Cisco Unified Communications Manager servers.
Transcoding and MTP
Transcoding compresses and decompresses voice streams to match endpoint-device capabilities.
Transcoding is required when an incoming voice stream is digitized and compressed (by means of a
codec) to save bandwidth, but the local device does not support that type of compression. Ideally, all IP
telephony devices would support the same codecs, but this is not the case. Rather, different devices
support different codecs.
Transcoding is processed by DSPs on the DSP farm; sessions are initiated and managed by Cisco Unified
Communications Manager which also refers to transcoders as hardware MTPs.
This feature provides transcoding at the remote site, without the need for access to the central site
(see
Figure 1 ).