Dial plans, About dial plans, Flat dial plan – TANDBERG Security Camera User Manual
Page 90: Structured dial plan, Hierarchical dial plan
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D14049.03
MAY 2008
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TANDBERG
VIDEO COMMUNICATIONS SERVER
ADMINISTRATOR GUIDE
Dial Plans
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 chose will depend on the complexity of your
system. Some possible options are described
in the following sections.
About Dial Plans
Flat Dial Plan
Structured Dial Plan
Hierarchical 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.
Whilst 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 and its Alternates.
An alternative deployment would use a
structured dial plan whereby 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
is configured with its corresponding area code
as a prefix (i.e. a
Match Mode
of
Pattern
and a
Type
of
Prefix
). That neighbor will now 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 neighbors 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 VCS
could be configured to strip prefixes before
sending the query to that zone.
A structured dial plan will minimize 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.
In this type of structure one VCS is nominated
as the Directory for the deployment, and all
other VCSs are neighbored with it alone. Each
VCS is configured with the Directory VCS as a
neighbor zone with a
Match Mode
of
Always
,
and the Directory VCS is configured with each
VCS as a neighbor zone with a
Match Mode
of
Pattern
and its prefix as the
Pattern String
.
There is no need to neighbor the VCSs with
each other. Adding a new VCS now only
requires changing configuration on that system
and the Directory VCS.
However, failure of the Directory VCS in this
situation could cause significant disruption
to communications. Consideration should be
given to the use of
for increased
resilience.