Structuring Your Dial Plan; Flat Dial Plan; Structured Dial Plan; Hierarchical Dial Plan - Cisco TelePresence Video Communication Server Administrator's Manual

Structuring your dial plan

As you start deploying more than one VCS, it is useful to neighbor the systems together so that they
can query each other about their registered endpoints. Before you start, you should consider how you
will structure your dial plan. This will determine the aliases assigned to the endpoints, and the way in
which the VCSs are neighbored together. The solution you choose will depend on the complexity of
your system. Some possible options are described in the following sections.

Flat dial plan

The simplest approach is to assign each endpoint a unique alias and divide the endpoint registrations
between the VCSs. Each VCS is then configured with all the other VCS as neighbor zones. When one
VCS receives a call for an endpoint which is not registered with it, it will send out a Location Request
to all the other neighbor VCSs.
While conceptually simple, this sort of flat dial plan does not scale very well. Adding or moving a VCS
requires changing the configuration of every VCS, and one call attempt can result in a large number of
location requests. This option is therefore most suitable for a deployment with just one or two VCSs
plus its peers.

Structured dial plan

An alternative deployment would use a structured dial plan where endpoints are assigned an alias
based on the system they are registering with.
If you are using E.164 aliases, each VCS would be assigned an area code. When the VCSs are
neighbored together, each neighbor zone would have an associated search rule configured with its
corresponding area code as a prefix (a Mode of Alias pattern match and a Pattern type of Prefix). That
neighbor would then only be queried for calls to numbers which begin with its prefix.
In a URI based dial plan, similar behavior may be obtained by configuring search rules for each
neighbor with a suffix to match the desired domain name.
It may be desirable to have endpoints register with just the subscriber number — the last part of the
E.164 number. In that case, the search rule could be configured to strip prefixes before sending the
query to that zone.
A structured dial plan minimizes the number of queries issued when a call is attempted. However, it
still requires a fully connected mesh of all VCSs in your deployment. A hierarchical dial plan can
simplify this.

Hierarchical dial plan

In this type of structure one VCS is nominated as the central VCS for the deployment, and all other
VCSs are neighbored with it alone.
The central VCS is configured with:
each VCS as a neighbor zone
n
search rules for each zone that have a Mode of Alias pattern match and the target VCS's prefix (as
n
with the structured dial plan) as the Pattern string
Each VCS is configured with:
the central VCS as a neighbor zone
n
a search rule with a Mode of Any alias and a Target of the central VCS
n
There is no need to neighbor the VCSs with each other. Adding a new VCS now only requires
changing configuration on the new VCS and the central VCS.
Cisco VCS Administrator Guide (X6.1)
Zones and neighbors
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