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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
About searches
One of the VCS’s functions is to process incoming requests to
search for a particular alias. These search requests are received
from:
•
locally registered endpoints
•
neighboring systems, including neighbors, traversal clients and
traversal servers
•
endpoints on the public internet
You can configure how the VCS searches its Local Zone and
external zones by setting up search rules that let you:
•
define alias, IP address and pattern matches to filter searches
to specific zones
•
define the order (priority) in which the search rules are applied
and stop applying any lower-priority search rules once a match
is found; this lets you reduce the potential number of search
requests sent out, and speed up the search process
•
set up different rules according to the source of the query
(such as the Local Zone, or any known zone)
•
apply zone transforms to modify an alias
You can configure up to 2000 search rules.
The VCS uses the protocol (SIP or H.323) of the incoming
call when searching a zone for a given alias. If the search
is unsuccessful the VCS may then search the same zone
again using the alternative protocol, depending on where the
search came from and the
Interworking mode
(
VCS configuration
> Protocols > Interworking
). If the request has come from a
neighboring system and
Interworking mode
is set to
RegisteredOnly
, the VCS searches the Local Zone using both
protocols, and all other zones using the native protocol only
(because it will interwork the call only if one of the endpoints is
locally registered). If
Interworking mode
is set to
On
, or the
request has come from a locally registered endpoint, the VCS
searches the Local Zone and all external zones using both
protocols.
About transforms
The VCS lets you transform the alias in a search request if it
matches certain criteria. This transformation can be applied to
the alias at two points in the search process: as a pre-search
transform, and as a zone transform.
Pre-search transform
Pre-search transforms are applied before any Call Policy, User
Policy or search rules are applied (see the
Pre-search transforms
section for more details).
Zone transform
Zone transforms are applied after Call Policy, User Policy and
the search rules have been applied, and let you change the alias
being searched for before a search request is sent to the Local
Zone or out to an external zone (see the
Zone searching and
transform process
, right). Zone transforms are specified as a part
of the
search rules
configuration.
You can transform an alias by removing or replacing its prefix,
suffix, or the entire string, and by the use of regular expressions.
Transforms support the use of Regular Expressions in
both the
Pattern String
and
Replace String
fields. See
the
Regular expression reference
Appendix for more
information.
Multiple search rules can refer to the same target zone.
This means that you can specify different sets of search
criteria and zone transforms for each zone.
For full information about configuring search rules, see the
Configuring search and zone transform rules
section.
Zone searching and transform process
Zone searching takes place after all pre-search transforms, Call
Policy and User Policy have been applied. The search rules and
zone transform process is as follows:
1. The VCS applies the search rules in priority order (all rules with
a priority of 1 are processed first, then priority 2 and so on) to
see if the given alias matches the rules criteria based on the
Source
of the query and the rule
Mode
.
2. If the match is successful, any associated zone transform
(where the
Mode
is
Alias Pattern Match
and the
Pattern
Behavior
is
Replace
) is applied to the alias.
3. The search rule's
Target zone
is queried (with the revised alias
if a zone transform has been applied) using the same protocol
(SIP or H.323) as the incoming call request. Note that if there
are many successful matches for multiple search rules at the
same priority level, every applicable
Target zone
is queried.
•
If the alias is found, the call is forwarded to that zone. If the
alias is found by more than one zone, the call is forwarded
to the zone that responds first.
•
If the alias is not found using the native protocol, the query
is repeated using the interworked protocol, depending on
the
Interworking mode
.
4. If the alias is not found, the search rules with the next highest
priority are applied (go back to step 1) until:
•
the alias is found, or
•
all target zones associated with search rules that meet the
specified criteria have been queried, or
•
a search rule with a successful match has an
On successful
match
setting of
Stop searching
Note the difference between a successful match (where
the alias matches the search rule criteria) and an alias
being found (where the query sent to the target zone is
successful). The
Stop searching
option provides better control
over the network's signaling infrastructure. For example, if
searches for a particular domain should always be routed to a
specific zone this option lets you make the search process more
efficient and stop the VCS from searching any other zones
unnecessarily.
Overview of searches and transforms
