When a call gets made across cluster through an intercluster trunk (ICT) and gets hairpinned back to the same location or site of the same cluster, although the media gets exchanged between two endpoints in the same site or location, the previous design of Cisco Unified Communications Manager location call admission control (CAC) deducted location bandwidth twice, once for the outbound call and again for the inbound call. The result did not correctly reflect the bandwidth consumption, which eventually caused denial of a new call to or from the site or location.
To resolve the bandwidth calculation problem, this feature enables Cisco Unified Communications Manager to pass location information, the primary key ID (PKID) of location record and location name, as a proprietary information element (IE) between the calling and called parties through an ICT, either in the H.323 protocol or SIP. Thus, either endpoint knows the true location information of the party/endpoint, not the location information of the ICT.
Cisco Unified Communications Manager previously identified Hub_None as the default location that has unlimited bandwidth, plus any user-created location to which the user can assign a device and for which the user can configure bandwidth.
A Cisco Unified Communications Manager location gets created specifically for the ICT for this type of application. This location, designated as the Phantom location, also has unlimited bandwidth. The locations server does not deduct bandwidth for a device that is assigned to the Phantom location. A device, such as the ICT, that is assigned to the Phantom location can use its own location or the true location of the connected device. Likewise, the outbound ICT can use its own location or the callee location, and the inbound ICT can use its own location or the caller location to deduct or adjust the bandwidth.
When the media connects, Cisco Unified Communications Manager adjusts the allocated location bandwidth according to the negotiated media codec. Cisco Unified Communications Manager can correctly readjust the location bandwidth on the basis of received callee location information for the outbound call. This enhancement helps the outbound call, which has reserved bandwidth during call setup time, to adjust the bandwidth back to 0 if the call gets hairpinned back to the same site or location.
Some supplementary services, such as transfer, can also hairpin the call back to the same site or location after the initial call setup process. Be aware that passing the location information of the final destination through the Notify signals (H.323) and re-INVITE signals (SIP) back to the calling cluster, so bandwidth can be adjusted to the right value, is also required.
Because location record PKID is uniquely defined within the Cisco Unified Communications Manager enterprise environment, Cisco Unified Communications Manager uses location record PKID to identify whether the call over ICT has looped back to the same cluster for the location-based CAC purpose. If other applications, like Cisco Voice Proxy (CVP), do not have access to the Cisco Unified Communications Manager database for location record PKID information, which comprises a string of characters and digits, applications may need to rely on the location name information that is getting passed around for the purpose of CAC. The same location name may exist for different locations with different location PKIDs in two different Cisco Unified Communications Manager clusters, which may cause confusion to the applications.
Cisco Unified Communications Manager Administration Configuration Tips
The Location Configuration window specifies the Phantom location as a location, besides the Hub_None location, that can get selected. Administrators cannot delete the Phantom location.
Administrators can create a default location for the Phantom location, similar to the Hub_None location. The Phantom location includes unlimited audio and video bandwidth value, and the administrator cannot modify the audio and video bandwidth values. The user can assign a location-pair RSVP policy between this location and other existing locations.
This feature does not entail any additional menu options or fields in Cisco Unified Communications Manager Administration. The Phantom value gets added for all entities that specify a location in the Location drop-down list box. You can find the Location field on the Device Pool Configuration, Annunciator Configuration, Music On Hold (MOH) Server Configuration, Conference Bridge Configuration, Voice Mail Port Configuration, Voice Mail Port Wizard Configuration, CTI Route Point Configuration, Gateway Configuration, Phone Configuration, Trunk Configuration, and Pilot Point Configuration windows.
Cisco Unified Communications Manager maintains the RSVP policy for the Phantom location during migration.
If the intercluster trunk or H.323 gateway gets configured in any other location besides the Phantom location, this feature does not work. In addition, if the intercluster trunk is connected to a third-party system that does not recognize and pass the Cisco-specific location information in the SIP or H.323 signals, this feature does not work.