Cisco Cisco Expressway
Using a policy service to route calls
When using external policy servers to control call routing, the CPL returned to the Expressway by the policy
server could change the destination alias of the call or add extra destinations. In these cases, the
Expressway will make another request to the policy server for the new or modified destination aliases.
server could change the destination alias of the call or add extra destinations. In these cases, the
Expressway will make another request to the policy server for the new or modified destination aliases.
This may be a desirable feature in some scenarios, but often in order to save resources it will not be desirable
for the policy server to fully process calls it has already routed, especially in the case of routing and forking
where loops or excessive forking could occur.
for the policy server to fully process calls it has already routed, especially in the case of routing and forking
where loops or excessive forking could occur.
To assist in managing these scenarios, the “GLOBAL_CALL_SERIAL_NUMBER” can be used to identify
calls that the policy server has already processed. This value is unique per call, across all Expressways.
calls that the policy server has already processed. This value is unique per call, across all Expressways.
Round-robin routing to a member of a group
In this example an administrator wants to route calls to the member of a group who has least recently
received a call. This requires an alias which represents members of a group and a list of the members within
that group. The administrator still wants to retain the ability for users to call other users directly.
received a call. This requires an alias which represents members of a group and a list of the members within
that group. The administrator still wants to retain the ability for users to call other users directly.
External Policy on Cisco Expressway Deployment Guide (X8.2)
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Appendix 1: Design examples