Cisco Unified Communications Manager and Interoperability Guide, Cisco IOS Release 12.4T
Overview of Cisco Unified Communications Manager and Interoperability
Overview of Cisco Unified Communications Manager and Interoperability
Last Updated: December 14, 2011
This chapter provides an overview of Cisco Unified Communications Manager and Cisco IOS interoperability.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Information About Cisco Unified Communications Manager and Interoperability
Cisco voice gateway routers can be deployed in a Cisco Unified Communications Manager IP-telephony network using the Cisco Architecture for Voice, Video, and Integrated Data (AVVID), a baseline infrastructure that enables enterprises to design networks that scale to meet e-business demands for business solutions such as e-learning and customer care.
Voice and video solutions based on Cisco AVVID include:
Cisco Unified Communications Manager Interoperability
Cisco Unified Communications Manager is the software-based call-processing component of voice gateways in a VoIP network. It extends enterprise telephony features and functions to packet telephony network devices such as IP phones, media processing devices, VoIP gateways, and multimedia applications.
Additional data, voice, and video services such as unified messaging, multimedia conferencing, collaborative contact centers, and interactive multimedia response systems interact through the Cisco Unified Communications Manager application programming interface (API). Cisco Unified Communications Manager also supports third-party applications.
Cisco IOS gateways connect AVVID networks to traditional telephone trunks or analog and digital devices. The trunks are connected to the PSTN or existing PBX systems, legacy telephones, and voice conference units. Cisco IOS voice gateways communicate with Cisco Unified Communications Manager using H.323 or Media Gateway Control Protocol (MGCP).
MGCP Voice Gateways
Cisco Unified Communications Manager provides a central point of configuration, administration, and control for MGCP voice gateways. Using Cisco IOS software, voice gateways are configured as MGCP gateways. Cisco Unified Communications Manager acts as an MGCP call agent, controlling the setting up and tearing down of connections between the endpoints in a VoIP network and endpoints in the public switched telephone network (PSTN), while managing all dial-plan related configuration elements.
With MGCP, dial plans are configured centrally in Cisco Unified Communications Manager, instead of in each gateway. All Cisco MGCP gateways in a Cisco AVVID-enabled IP telephony network can be automatically configured by downloading XML files from Cisco Unified Communications Manager. Cisco MGCP gateways also provide multiple levels of failover capabilities, including Survivable Remote Site Telephony (SRST) support to prevent call-processing interruptions or dropped calls if there is a Cisco Unified Communications Manager or WAN failure.
MGCP gateways support the following Cisco Unified Communications Manager features:
MGCP Gateway Fallback
MGCP gateway fallback improves the reliability of PSTN interfaces in an IP-telephony network by providing basic call processing support when an MGCP gateway loses connectivity to all of its configured Cisco Unified Communications Manager servers. Each Cisco Unified Communications Manager server is potentially available as a backup call agent through a prioritized list of call agents that is configured on the MGCP gateway.
On startup, the MGCP voice gateway attempts to establish a connection to the highest order Cisco Unified Communications Manager server on the configured list. If the attempt is successful, the gateway registers itself with the primary (highest priority) call agent. If no call agent in this prioritized list is accessible, the gateway uses its default H.323 session application (Version 2) to perform basic call-handling functions (see the figure below).
MGCP PRI Backhaul
MGCP PRI backhaul is a method for transporting complete IP telephony signaling information from an ISDN PRI interface on an MGCP gateway to Cisco Unified Communications Manager through a Transmission Control Protocol (TCP) connection. It terminates all of the ISDN PRI Layer 2 (Q.921) signaling functions on the MGCP gateway and packages all of the ISDN PRI Layer 3 (Q.931) signaling information into packets for transmission to Cisco Unified Communications Manager through an IP tunnel. This ensures the integrity of the Q.931 signaling information that passes through the network for managing IP telephony devices.
MGCP BRI Backhaul
MGCP-controlled backhaul of BRI signaling provides service to remote-office gateways that connect by means of ISDN BRI trunks to a centralized Cisco Unified Communications Manager. D-channel signaling information is backhauled to Cisco Unified Communications Manager through a TCP session. All Q.931 messages are passed through the TCP connection between the Cisco MGCP gateway and Cisco Unified Communications Manager. The feature enables you to connect remote ISDN PBXs and key systems to a Cisco ISDN BRI network termination (network side) or a PSTN Class 4/5 switch through a Cisco ISDN BRI terminal equipment (as user side) interface.
Multicast music-on-hold (MOH) functionality enables the streaming of music from an MOH server to the voice interfaces of on-net and off-net callers that are placed on hold. This integrated multicast capability is implemented through the H.323 signaling in Cisco Unified Communications Manager.
Network Specific Facilities
The MGCP Gateway Support for Cisco Unified Communications Manager Network Specific Facilities (NSF) feature supports the use of the ISDN NSF information element in the route pattern, enabling facilities or services to be invoked on a call-by-call basis. Without NSF configuration, you must configure associated gateways as standalone H.323 gateways for which NSF services are configured locally within the router. No configuration is required on the MGCP gateway to use the NSF feature.
When you configure MGCP gateways to interoperate with Cisco Unified Communications Manager, you can use a centralized TFTP boot directory on a host device in your network to automatically download most of the Cisco IOS configuration in an XML file. A Cisco Unified Communications Manager server can be concurrently configured as a TFTP server.
The XML file is generated by using the web-based Cisco Unified Communications Manager graphical user interface (GUI). When the network administrator changes the configuration information in the database, Cisco Unified Communications Manager instructs the MGCP gateway to download the modified XML file.
Supplementary services include call forwarding, call hold, call transfer when the line is busy or there is no answer, and three-party call conferencing to and from the PSTN or a private branch exchange (PBX).
A Cisco MGCP gateway first connects--that is, registers--to a primary Cisco Unified Communications Manager. If connection to the primary fails, the gateway registers automatically to a backup if one exists and, if that connection also fails, to a second backup if one exists. When connection to the primary is restored, the gateway automatically registers to the primary. Existing connections are preserved during the switchover.
Switchback is the process that MGCP gateways use to reestablish communication with the primary Cisco Unified Communications Manager server when it becomes available after losing connectivity. Switchback mode can occur immediately, at a specified time after the last active call ends, or after a specified length of time. During the switchback, existing connections are preserved.
Tones and Cadences
Tones and cadences are preconfigured based on the network locale in Cisco Unified Communications Manager. It is no longer necessary to configure the cptone command on the MGCP gateway. The static tone table used for a voice port is determined by the network locale that is specified for the voice port in Cisco Unified Communications Manager. The network locale for each voice port is downloaded in the gateway's XML configuration file.
The Customizable Tone Download to Cisco IOS MGCP Gateways from Cisco Unified Communications Manager feature enables the downloading of region-specific tones and the associated frequencies, amplitudes, and cadences in up to two custom tone files.
MGCP Advantages Over H.323
Using MGCP provides advantages over H.323, including the following:
MGCP enables external control of network signaling. Handling of Layer 3 call processing centrally in the network is advantageous to network operators who need a high degree of control over their networks.
MGCP speeds voice cut-through as compared to H.323 for both initial call setup and redirects. Voice cut-through is the time from when the called party goes offhook to when both parties are able to receive voice from the other. Long cut-through times can prevent deployment of viable IP telephony solutions in centralized environments.
Conferencing and Transcoding
The digital-signal-processor (DSP) farm functionality on Cisco IOS gateways provides conference, transcode, and hardware MTP capability by using DSP resources on high-density digital voice/fax network modules such as the NM-HDV and NM-HDV2. DSP farms are configured on the voice gateway and managed by Cisco Unified Communications Manager through Skinny Client Control Protocol (SCCP).
Toll Fraud Prevention
When a Cisco router platform is installed with a voice-capable Cisco IOS software image, appropriate features must be enabled on the platform to prevent potential toll fraud exploitation by unauthorized users. Deploy these features on all Cisco router Unified Communications applications that process voice calls, such as Cisco Unified Communications Manager Express (CME), Cisco Survivable Remote Site Telephony (SRST), Cisco Unified Border Element (UBE), Cisco IOS-based router and standalone analog and digital PBX and public-switched telephone network (PSTN) gateways, and Cisco contact-center VoiceXML gateways. These features include, but are not limited to, the following:
For more configuration guidance, see the "Cisco IOS Unified Communications Toll Fraud Prevention" paper.
The following sections provide references for Cisco IOS Interoperability with Cisco Unified Communications Manager.
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