Calling Search Space
A calling search space is an ordered list of partitions that a user can search before being allowed to place a call. Calling search spaces are assigned to devices that can initiate calls. These include IP phones, Cisco SoftPhones, and gateways.
Dialing restrictions are simple to invoke because users can dial only the partitions in the calling search space to which they are assigned. Dialing a directory number outside an allowed partition causes the caller to receive a busy signal.
An analogy can be drawn between partitions and calling search spaces and routers with access control lists (ACLs). Think of a partition as an IP subnet where you place users. A calling search space is analogous to an inbound ACL that dictates which subnet you can reach.
Figure 5-5 illustrates the analogy of partitions and calling search spaces to ACLs. Figure 5-5 Partition/Calling Search Space-Subnet/ACL Analogy
Inbound access-list/ calling search space
You can reach these subnets/partitions
Figure 5-6 is a simple example of how partitions and calling search spaces can be used to provide dialing restrictions.
Figure 5-6 is a simple example of how partitions and calling search spaces can be used to provide dialing restrictions.
Subnet/ partition A
Subnet/ partition B
Subnet/ partition C
H Configuring Dial Plan Groups and Calling Restrictions
Figure 5-6 Partitions and Calling Search Spaces Used to Provide Dialing Restrictions
- Headquarters
Partition assignment
"SJ-Users" = All SJ IP phones "SJ-PSTN" = "9" route pattern
Calling search space
"Unrestricted" = SJ-Users, SJ-PSTN "SJ-Only" = SJ-Users
IP phone calling search space assignment
Staff IP phones = "Unrestricted" Lobby IP phones = "SJ-Only"
Staff - may dial anywhere Lobby phones - only can dial internal users
In Figure 5-6, staff employees have unrestricted dialing, whereas the lobby phones have the ability to dial people within the local site only. All IP phones are placed in the SJ-Users partition, and the route pattern 9 associated with the PSTN is placed in the SJ-PSTN partition. Two calling search spaces are created that denote two different dialing characteristics. A calling search space called Unrestricted is created that contains both SJ-Users and SJ-PSTN partitions. A
Configuring Dial Plan Groups and Calling Restrictions I
second calling search space called SJ-Only is created and contains only the SJ-Users. San Jose staff IP phones are assigned the Unrestricted calling search space, which means they are allowed to dial anywhere. The lobby phones are assigned the SJ-Only calling search space, which means they can dial only local phones within the local site.
The partition and calling search space assignments used to configure the preceding example are shown in Table 5-1 and Table 5-2. Two partitions define the reachability characteristics for the given site, one for internal local site users and one for external calls. Devices and route patterns are placed in these partitions.
|
Partition Name |
Designated Devices Assigned to Partition |
|
SJ-Users |
All IP phones within San Jose |
|
SJ-External |
All externally destined route patterns (local PSTN) |
|
Calling Party Search Space |
Partitions |
Assigned To |
|
Unrestricted |
SJ-Users |
Devices that can make internal |
|
SJ-External |
and external calls |
|
|
SJ-Only |
SJ-Users |
Devices that can make internal |
|
calls only |
This example represents perhaps the simplest configuration for the requirements of multisite WAN local call processing. A more ambitious dial plan could include the following considerations:
• Intrasite calls only
• Intrasite and local emergency calls only
• Intra- and intersite calls only
• Intrasite, intersite, and local emergency calls only
• Intrasite, intersite, local emergency, and local PSTN calls only
H Dial Plan Guidelines and Configuration
• Intrasite, intersite, local emergency, and national long-distance PSTN calls only
• Fully unrestricted dialing, including international numbers
Partitions and calling search spaces permit independent dial ranges on a partition basis. This means that extensions and access codes within different partitions can have overlapping numbers and yet function independently. The most common application of this is in a centralized call processing system where all sites and users share the same Cisco CallManager, yet each site can dial a 9 for local PSTN access. This is a new capability in Cisco CallManager Release 3.0. In prior releases, each remote site had to have its unique PSTN access code.
The following conditions apply with regard to overlapping users and extensions at different sites with the centralized call processing system:
• Overlapping internal dial plans at different sites are supported only if voice mail is not required. When Cisco CallManager sends a call to voice mail, it cannot determine for which partition (and therefore which voice mail user) the call is intended. For example, user 1111 at site A cannot be distinguished from user 1111 at site B when the call is sent to voice mail. Voice mail users must have unique IDs.
• If voice mail is not required, users that share extensions at different sites can be reached by the following means:
- PSTN—by dialing the local access code followed by the fully qualified directory number.
- IP WAN—by using translation tables, which can allow for prepending of overlapping numbers with a unique steering code that is stripped off when the call is delivered to the destination partition.
Continue reading here: Interaction Between Cisco Call Manager and Gatekeeper
Was this article helpful?