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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.
Overview and
System
Introduction
status
configuration
D14049.07
March 2010
Overview of searches and transforms
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
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
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
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
VCS
Zones and
Clustering and
configuration
neighbors
peers
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
Pre-search transforms
2. If the match is successful, any associated zone transform
3. The search rule's Target zone is queried (with the revised alias
Zone searching and
4. If the alias is not found, the search rules with the next highest
Appendix for more
section.
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.
Call
Bandwidth
processing
control
88
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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.
(where the Mode is Alias Pattern Match and the Pattern
Behavior is Replace) is applied to the 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.
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
Firewall
Applications
Maintenance
traversal
ADMINISTRATOR GUIDE
Appendices
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