Calling Privileges

Calling privileges control the available components of a call-routing database that are accessible to an endpoint. The primary application is the implementation of CoS. CoS is usually used to control telephony charges by blocking costly service numbers. Many organizations block international calls for most users and restrict long-distance dialing on common-area phones. CoS is also used to protect the privacy of some users. Executive managers may allow only those calls that have gone through their assistants, for example.

Calling privileges can also be used to implement special applications such as tail-end hop off (TEHO). TEHO allows organizations to save public switched telephone network (PSTN) toll charges by routing long-distance and international calls across the private IP WAN network before hopping off at the destination-site gateway to route a local PSTN call. TEHO is an application of least-cost routing (LCR), which has been in telephony networks for a very long time.

TEHO can greatly complicate a dial plan because of the additional configuration required to properly route calls on a per-site basis. In a multisite environment with PSTN gateways at each site, PSTN route patterns should always be routed to the local PSTN gateway; hence, the same route patterns have to exist multiple times (once per site in this example), and only the site-specific route patterns should be accessible by the devices located at this site.

Another application is time-of-day routing, where calls should take different paths depending on the time when the call is placed.

Table 13-1 provides a typical CoS implementation with calling classes and their allowed destination. These calling classes can then be assigned to devices or users.

In the example, class Internal allows only internal and emergency calls. Class Local adds the permission for local PSTN calls, class Long Distance also allows long-distance PSTN calls, and class International also enables international PSTN calls.

Table 13-1 Class of Service Example

Class of Service

Allowed Destinations

Internal

Internal

Emergency

Local

Internal

Emergency

Local PSTN

Table 13-1 Class of Service Example (Continued)

Class of Service

Allowed Destinations

Long Distance

Internal Emergency Local PSTN Long-distance PSTN

International

Internal Emergency Local PSTN Long-distance PSTN International PSTN

Table 13-2 briefly describes the various call-privilege configuration elements that this chapter covers.

Table 13-2 Call-Privileges Configuration Elements

Element

Characteristic

Partition

Group of numbers with similar reachability characteristics (including route patterns, directory numbers, translation patterns, and so on)

Calling search space

Ordered list of accessible partitions applied to device to restrict call privileges

Time periods

Static days or recurring time intervals

Time schedules

Ordered list of time periods

CMCs

Used to track calls to certain destinations

FACs

Restrict outgoing calls to certain numbers

Was this article helpful?

0 0

Post a comment