91
D14049.07
March 2010
Grey Headline
(continued)
TANDBERG
VIDEO COMMUNICATION SERVER
ADMINISTRATOR GUIDE
Introduction
Overview and
status
System
configuration
VCS
configuration
Zones and
neighbors
Clustering and
peers
Call
processing
Bandwidth
control
Firewall
traversal
Appendices
Applications
Maintenance
Searches and transforms
Fallback alias
The VCS could receive a call that is destined for it but which
does not specify an alias. This could be because:
•
the caller has dialed the IP address of the VCS directly
•
the caller has dialed a domain name belonging to the VCS
(either one of its configured SIP domains, or any domain that
has an SRV record that points at the IP address of the VCS),
without giving an alias as a prefix
Normally such calls would be disconnected. However, the VCS
allows you to specify an alias to which all such calls should
be routed. This alias is known as the
fallback alias
and is
configured on the
Search rules configuration
page (
VCS
configuration > Search rules > Configuration
).
To configure this setting using the CLI:
•
xConfiguration Call Services Fallback Alias
If no fallback alias is configured, calls that do not specify
an alias will be disconnected.
Some endpoints do not allow users to enter an alias and
an IP address to which the call should be placed.
Example usage
You may want to configure your fallback alias to be that of your
receptionist, so that all calls that do not specify an alias are still
answered personally and can then be redirected appropriately.
For example, Example Inc. has the domain of
example.com
. The
endpoint at reception has the alias
.
They configure their VCS with a fallback alias of
reception@
example.com
. This means that any calls made directly to
example.com
(i.e. without being prefixed by an alias), are
forwarded to
, where the receptionist
answers the call and directs it appropriately.
Search configuration
Calls to unknown IP addresses
Although the VCS supports dialing by IP address, it is sometimes
undesirable for a VCS to be allowed to place a call directly to an
IP address that is not local. Instead, you may want a neighbor to
place the call on behalf of the VCS, or not allow such calls at all.
The VCS lets you configure how it behaves when receiving a call
for an IP address that is not local through the
Calls to Unknown
IP addresses
setting on the
Search rules configuration
page
(
VCS configuration > Search rules > Configuration
).
To configure this setting from the CLI:
•
xConfiguration Call Services
CallsToUnknownIPAddresses
About unknown IP addresses
The VCS considers an IP address to be "known" if it either:
•
is the IP address of a locally registered endpoint
•
falls within the IP address range of one of the subzone
membership rules configured on the VCS
Calls to these IP addresses are not affected by the
Calls to
Unknown IP addresses
setting - the VCS will always attempt to
place the call (providing there is a search rule for
Any IP Address
against the Local Zone). All other IP addresses are considered to
be "unknown" and are handled by the VCS according to its
Calls
to Unknown IP addresses
setting.
About unregistered endpoints
An unregistered endpoint is any device that is not registered
with an H.323 gatekeeper or SIP registrar (e.g. VCS, gatekeeper
or TANDBERG Border Controller). Although most calls are made
between endpoints that are registered with such systems, it is
sometimes necessary to place a call to an unregistered endpoint.
There are two ways to call to an unregistered endpoint:
•
by dialing its URI (this requires that the local VCS is configured
to support URI dialing, and a DNS record exists for that URI
that resolves to the unregistered endpoint's IP address)
•
by dialing its IP address
Calls to Unknown IP addresses settings
The options for the
Calls to Unknown IP addresses
setting are:
Direct
: the VCS attempts to place the call directly to the unknown
IP address without querying any neighbors.
Indirect
: the VCS forwards the search request to its neighbors in
accordance with its normal search process, meaning any zones
that are the target of search rules with an
Any IP Address
mode.
If a match is found and the neighbor’s configuration allows it to
connect a call to that IP address, the VCS will pass the call to
that neighbor for completion.
Off
: the VCS will not attempt to place the call, either directly or to
any of its neighbors.
This setting applies to the call's destination address prior
to any zone transforms, but after any pre-search
transforms, Call Policy or User Policy rules have been
applied.
In addition to controlling calls, this setting also
determines the behavior of provisioning and presence
messages to SIP devices, as these messages are routed
to IP addresses.
Recommended configuration for firewall traversal
When the VCS Expressway is neighbored with a VCS Control for
firewall traversal, you should typically set
Calls to unknown IP
addresses
to
Indirect
on the VCS Control and
Direct
on the VCS
Expressway. When a caller inside the firewall attempts to place
a call to an IP address outside the firewall, it will be routed as
follows:
1. The call will go from the endpoint to the VCS Control with
which it is registered.
2. As the IP address being called is not registered to that VCS,
and its
Calls to unknown IP addresses
setting is
Indirect
,
the VCS will not place the call directly. Instead, it will query
its neighbor VCS Expressway to see if that system is able to
place the call on the VCS Control’s behalf.
3. The VCS Expressway receives the call and because its
Calls to
unknown IP addresses
setting is
Direct
, it will make the call
directly to the called IP address.
