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TANDBERG Border Controller User Manual
8 Call Policy
Your TANDBERG Border Controller allows you to set up policy to control which calls are allowed
and even redirect selected calls to different destinations. You specify this policy by uploading a
script written in the Call Processing Language (CPL). Each time a call is made the
Border Controller executes the script to decide, based on the source and destination of the call,
whether to
• Proxy the call to its original destination
• Redirect the call to a different destination
• Reject the call.
The Border Controller will only execute scr ipts for source or destinations which are registered
directly with the system.
The CPL script is uploaded via the Web interface under the Border Controller Configuration →
Files web page.
The execution of the CPL script is controlled by the setting
xConfiguration Gatekeeper Policy Mode <On/Off>
Policy interacts with authentication (section 5.2). If authentication is enabled on the local Border
Controller and a call is received from a remote, unauthenticated Gatekeeper, the call’s source
aliases wil l be removed from the call request before it is passed to the policy engine. This is
because the unauthenticated source aliases could be forged and so should not be used for policy
decisions in a secure environment.
The following sections give details of the Border Controller’s implementation of the CPL language
and should be read on conjunction with the CPL standard (RFC 3880[5]).
8.1 Making Decisions Based on Addresses
8.1.1 address-switch
The address-switch node allows the scr i pt to run different actions based o n the source or
destination aliases of the call. The address-switch sp ecifie s which fields to match and then a list
of address nodes contains the possible matches and their associated actions.
The supported attributes on an address-switch and their interpretation are as follows:
field
origin Match against the source aliases.
destination Match against the destination aliases.
original-destination Match against the destination aliases.
If the selected field contains multiple aliases then the Border Controller will attempt to match
each address node with all of the aliases before proceeding to the next address node i.e. an
address node matches if it matches any alias.
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