In order for an endpoint to use the TANDBERG VCS as its H.323
gatekeeper or SIP Registrar, the endpoint must first register with
the VCS. The VCS can be configured to control which devices
are allowed to register with it. Two separate mechanisms are
provided:

•

authentication process

based on the username and

password supplied by the endpoint
a simple Registration Restriction Policy that uses

•

Allow Lists

or Deny Lists

to specify which aliases can and cannot register

with the VCS.

It is possible to use both mechanisms together. For example,
you can use authentication to verify an endpoint’s identity from a
corporate directory, and registration restriction to control which
of those authenticated endpoints may register with a particular
VCS.
This section gives an overview of how endpoints and other
devices register with the VCS, and then describes the two
mechanisms by which registrations can be restricted.

Registration Overview

MCU, Gateway and Content Server Registration

H.323 systems such as gateways, MCUs and Content Servers
can also register with a VCS. They are known as locally
registered services. These systems are configured with their
own prefix, which they provide to the VCS when registering. The
VCS will then know to route all calls that begin with that prefix
to the gateway, MCU or Content Server as appropriate. These
prefixes can also be used to control registrations.
SIP devices cannot register prefixes. If your dial plan dictates
that a SIP device should be reached via a particular prefix, then
you should add the device as a neighbor zone with a pattern
match equal to the prefix to be used.

Registrations on a VCS Expressway

If a traversal-enabled endpoint registers directly with a VCS
Expressway, the VCS Expressway will provide VCS services to
that endpoint in addition to firewall traversal. Traversal-enabled
endpoints include all TANDBERG Expressway™ endpoints and
third party endpoints which support the ITU H.460.18 and
H.460.19 standards.
Endpoints that are not traversal-enabled can still register with
a VCS Expressway, but they may not be able to make or receive
calls through the firewall successfully. This will depend on a
number of factors:

whether the endpoint is using SIP or H.323

•

the endpoint’s position in relation to the firewall

•

whether there is a NAT in use

•

whether the endpoint is using a public IP address.

•

For example, if an endpoint is behind a NAT or firewall, it may not
be able to receive incoming calls and may not be able to receive
media for calls it has initiated. SIP endpoints can also work
behind a NAT but can only receive video if they send it as well.
To ensure firewall traversal will work successfully for H.323
endpoints behind a NAT, the endpoint must be traversal-enabled.

The TANDBERG MPS and TANDBERG Content Server
(TCS) both support Expressway. They can therefore
register directly with a VCS Expressway for firewall

traversal.