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 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 any other traversal call, 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.
Calls passing through the Traversal Subzone will consume an
amount of bandwidth within the 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 include:

calls that are traversing a firewall
SIP to H.323 interworking calls
IPv4 to IPv6 interworking calls.

Traversal calls use more resource that 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.

•
•
•

About the Default Subzone

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 specified 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.

Specifying the IP Address Range of a Subzone

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.

Default Settings

The VCS is shipped with the Default Subzone, 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 DefaultLinksAdd

To restore this link via the web interface, you must recreate it
manually. See

Creating Links

for instructions on how to do this.

•

About the Traversal Subzone

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.

Subzones

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.

Bandwidth Control