.....from previous
Classes of Service with the Line/Device Approach - Multi-Site Deployments
The traditional approach outlined in the preceding section can result in a large number of partitions and calling search spaces when applied to large multisite deployments with centralized call processing. This configuration is required because the device calling search space is used to determine both the path selection (which PSTN gateway to use for external calls) and the class of service.
It is possible to significantly decrease the total number of partitions and calling search spaces needed by dividing these two functions between the line calling search space and the device calling search space, in what is called the line/device approach.
Keeping in mind how the line calling search space and the device calling search space for each given IP phone are combined within Cisco Unified CallManager, and how the line calling search space partitions appear first in the resulting calling search space (see Calling Privileges in Cisco Unified CallManager), you can apply the following general rules to the line/device approach:
•Use the device calling search space to provide call routing information (for example, which gateway to select for PSTN calls).
•Use the line calling search space to provide class-of-service information (for example, which calls to allow).
When applied to centralized call processing deployments with large numbers of sites, the line/device approach drastically reduces the number of partitions and calling search spaces needed. For example, a deployment with 100 remote sites and 4 classes of service requires at least 401 partitions and 400 calling search spaces with the traditional approach but only 105 partitions and 104 calling search spaces with the line/device approach.
However, the line/device approach relies on the fact that you can globally identify the types of PSTN calls that must be restricted for certain classes of service (for example, local, long-distance, and international calls). If the national numbering plan of your country does not allow this global identification of the different types of calls, the efficiency of this approach (in terms of configuration savings) is lower than that indicated in the formulas above.
For example, in France the numbering plan is based on five area codes, from 01 to 05 (plus the 06 area code for cellular phones), followed by eight digits for the subscriber number. The key characteristic is that each PSTN destination is reached by dialing exactly the same number (for example, 01XXXXXXXX for Paris numbers, 04XXXXXXXX for Nice numbers, and so on), whether calling from the same local area or from a different area. This means that it is not possible to block access to long-distance calls with a single partition and a single route pattern because the concept of "long-distance call" changes depending on the area where the calling party is located. (For example, a call to 014455667788 is a local call if the caller is in Paris but a long-distance call is the caller is in Nice or Lyon.)
In such cases, you will have to configure additional sets of blocking calling search spaces and partitions, one for each area within which local and long distance calls are dialed the same way. In the example of France, you would have to defining five additional blocking calling search spaces and partitions, one for each area code.
Described in detail in the CCM - SRND;
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/4x/42dialpl.html#wp1044899
And nicely shown here;
Voice Dial Plan Interactive Voice Network Configuration Example
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a00807f54af.shtml
Hope this helps!
Rob
