External Policy Overview; Using An External Policy Server - Cisco TelePresence Administrator's Manual

Reference material

External policy overview

The Cisco TelePresence Video Communication Server (VCS) has built in support for Registration Policy,
Call Policy and User Policy (FindMe) configuration. It also supports CPL (Call Processing Language) for
implementing more complex policy decisions. CPL is designed as a machine-generated language and is not
immediately intuitive; while the VCS can be loaded with CPL to implement advanced call policy decisions,
complex CPL is difficult to write and maintain.
The VCS's external policy feature allows policy decisions to be taken by an external system which can then
instruct the VCS on the course of action to take (such as whether to accept a registration, fork a call and so
on). Call policy can now be managed independently of the VCS, and can implement features that are
unavailable on the VCS. The external policy server can make routing decisions based on data available from
any source that the policy server has access to, allowing companies to make routing decisions based on
their specific requirements.
When the VCS is configured to use an external policy server the VCS sends the external policy server a
service request (over HTTP or HTTPS), the service will send a response back containing a CPL snippet
which the VCS will then execute.

Using an external policy server

The main areas where the VCS can be configured to use an external policy server are:
Registration Policy – to allow or reject registrations.
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Call Policy (also known as Admin Policy) – to control the allowing, rejecting, routing (with fallback if calls
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fail) and forking of calls.
Search rules (policy can be applied for specific dial plan search rules).
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Each of these areas can be configured independently of each other as to whether or not to use a policy
service. If a policy service is used, the decisions made by the policy service replace (rather than supplement)
those made by the VCS.
When configuring policy services:
Up to 3 external policy servers may be specified to provide resiliency (and not load balancing).
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Default CPL can be configured, to be processed by the VCS as a fallback, if the service is not available.
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The status and reachability of the service can be queried via a status path.
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If you require FindMe functionality beyond that provided by VCS / Cisco TMS, we recommend that you
implement it through Call Policy.
Cisco VCS Administrator Guide (X8.1.1)
External policy overview
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