TANDBERG Compliance Appliance Deployment Manual - page 21
6 Implementing the compliance policy
17
6.3.2 How the VCS and TCA work together
TCA works in much the same way as a VCS in ‘traversal mode’ in which the actual media stream is
routed through the VCS. Each endpoint is registered to a specific VCS which identifies the endpoint by
its IP address and URI. To enable TCA to record a call, the VCS has to pass the IP addresses of the
endpoints to it.
The process followed by the VCS when attempting to locate a destination endpoint is described below.
1
The user enters into their endpoint the alias or address of the destination endpoint.
2
The destination address is sent from the caller’s endpoint to its local VCS (i.e. the VCS to which it
is registered).
3
The VCS applies any pre-search transforms to the alias.
4
The VCS applies any Call Policy to the (transformed) alias. If this results in a new alias, the process
starts again, with the new alias checked against the pre-search transforms. In the case of a TCA Call
Policy the policy can match either the initiating or receiving endpoint alias to see if either is
required to be recorded. If either of them does, the VCS appends the prefix ‘CAREC (compliance
appliance recording) to the alias (e.g. ‘j.smith@gmb.com’ becomes ‘CAREC.j.smith@gmb.com’).
5
The VCS applies any User Policy (if FindMe is enabled) to the alias. If the alias is a FindMe name
that resolves to one or more new aliases, the process will start again; all the resulting aliases will be
checked against pre-search transforms and Call Policy.
6
The VCS then searches, in order of priority, all its zone matches, including those configured on the
Local Zone (which includes any cluster peers). At each priority, zones are searched first in the
native protocol and then, if the VCS interworking configuration allows, the alternative protocol. If
the alias matches an ENUM zone, this may return a URI. If so, the process starts again; the URI is
checked against any pre-search transforms, Call Policy and User Policy. In the case of a TCA Call
Policy all aliases prefixed with CAREC are responded as “found” by the TCA.
7
If the alias is found within the Local Zone or by one of the external zones, the VCS will attempt to
place the call to that zone.
8
If the alias is not found, the VCS will respond with a message to say that the call has failed.
9
Once the call is placed by the VCS to the TCA, the TCA then strips off the CAREC prefix and then
sends the original alias to the VCS, it then gains the true destination address from the VCS or it’s
neighbored zones and completes the call.
Note that the above is somewhat simplified, see section
11 Call Flow within TCA
for a detailed description
of how the call flow works within the TCA and the
Call processing
section of the
VCS Administrator Guide
for more information as to how the VCS processes calls.
6.3.3 Using zones to manage TCAs
Depending on how your endpoints and VCSs are configured, you can use zones to direct calls to
particular TCAs. For example, if a call comes from London, which is defined as ‘Zone UK’, you can
rout all the calls in that zone to a TCA in London.