All endpoints registered with the VCS are part of its Local Zone.
The Local Zone is made up of two or more subzones. The first two subzones are automatically
created for you. These are the

Default Subzone

and the

Traversal Subzone

. You can create and

configure further subzones manually on the basis of endpoints’ IP addresses: when an endpoint
registers with the VCS its IP address is checked and it is assigned to the appropriate subzone.
The main purpose of all three types of subzones is to enable you to control the bandwidth used by
various parts of your network.

Bandwidth Consumption of Traversal Calls

Traversal calls between two endpoints within a single subzone on the VCS must, like all traversal
calls, pass through the VCS’s Traversal Subzone. This means that such calls will consume an
amount of bandwidth from the originating subzone’s total concurrent allocation that is equal to
twice the bandwidth of the call – once for the call from the subzone to the Traversal Subzone, and
again for the call from the Traversal Subzone back to the originating subzone.
In addition, since this call passes through the Traversal Subzone, it will consume an amount of
bandwidth from the Traversal Subzone equal to that of the call.

Traversal Calls

A traversal call is any call passing through the VCS that includes both the signaling (information
about the call) and media (voice and video). The only other type of call is a non-traversal call,
where the signaling passes through the VCS but the media goes directly between the endpoints.
Traversal calls are always one of the following:

calls that are traversing a firewall

•

SIP to H.323 interworking calls

•

IPv4 to IPv6 interworking calls.

•

Traversal calls use more resource than non-traversal calls, and the numbers of each type of call
are licensed separately. The VCS has one license for the maximum number of concurrent traversal
calls it can take, and another for the maximum number of concurrent non-traversal calls.

When an endpoint registers with the VCS, its IP address is checked and it is assigned to the
appropriate subzone. If no subzones have been created, or the endpoint’s IP address does not
match any of the configured subzones, it will be assigned to the Default Subzone.
The use of a Default Subzone on its own (i.e. without any other manually configured subzones)
is suitable only if you have uniform bandwidth available between all your endpoints. However, it
is possible for a Local Zone to contain two or more different networks with different bandwidth
limitations. In this situation, you should configure separate subzones for each different part of the
network.

A subzone is defined by specifying a range of
IP addresses. The VCS allocates endpoints
to a subzone based on their IP address. You
specify which IP addresses are associated with
the subzone by configuring up to 5 subnets for
that subzone.

The VCS is shipped with the Default Subzone
and Traversal Subzone (and

Default Zone)

already created, and with links between the
three. You may delete or amend these default
links if you need to model restrictions of your
network.
If any of these links have been deleted, they
may be automatically restored via:

xCommand DefaultLinksAd

•

To restore these links via the web interface,
you must recreate them manually. See

Creating Links

for instructions on how to do

this.

The Traversal Subzone is a conceptual subzone. No endpoints can be registered to the Traversal
Subzone; its sole purpose is to allow for the control of bandwidth used by

traversal calls

All traversal calls are deemed to pass through the Traversal Subzone, so by applying bandwidth
limitations to the Traversal Subzone you can control how much processing of media the VCS will
perform at any one time. These limitations can be applied on a total concurrent usage basis, and/
or on a per-call basis.

About Subzones and Bandwidth Control

A call is “traversal” or “non-traversal” from the point of view of the VCS through which it is
being routed at the time. A call between two endpoints may pass through a series of VCSs.
Some of these systems may just take the signaling, in which case the call will be a

non-traversal call for that VCS. Other systems in the route may need to take the media as well, and
so the call will count as a traversal call on that particular VCS.

If an endpoint’s IP address matches
more than one subnet, it will be
allocated to the subnet with the

narrowest range.

About the Traversal Subzone

About the Default Subzone

Subzone Links

Specifying the Subzone IP Addresses