Structuring Your Dial Plan; Flat Dial Plan; Structured Dial Plan; Hierarchical Dial Plan - Cisco TelePresence 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 directory VCS for the deployment, and all other
VCSs are neighbored with it alone.
The directory 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 with the
n
structured dial plan) as the Pattern string
Cisco VCS Administrator Guide (X7.1)
Zones and neighbors
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