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D 14049.01
07.2007
82
TANDBERG VIDEO COMMUNICATION SERVER
ADMINISTRATOR GUIDE
Text goes here
Introduction
Getting
Started
System
Overview
System
Configuration
H.323 & SIP
Configuration
Registration
Control
Zones and
Neighbors
Call
Processing
Firewall
Traversal
Bandwidth
Control
Maintenance
Appendices
TANDBERG
ADMINISTRATOR GUIDE
TANDBERG VIDEO COMMUNICATION SERVER
ADMINISTRATOR GUIDE
Call
Processing
URI Dialing
URI Dialing for Outgoing Calls
Process
When a user places a call using URI dialing, they will typically dial an address in the form name@
example.com from their endpoint. Below is the process that is followed when a URI address is
dialed from an endpoint registered with your VCS:
The VCS will check its own list of registrations, and those of its Alternates, to see if the
address is registered locally.
If the address is not registered locally, the VCS will check all its zones to see if any of them are
configured with either:
an AlwaysMatch, or
a PatternMatch with a pattern that matches the URI address.
These zones will then be queried in priority order for the URI.
If one or more of the zones that contain a match are neighbor zones, the neighbor will be
queried for the URI. If the neighbor supports URI dialing, it may route the call itself.
If one or more of the zones that contain a match are DNS zones, this will trigger the VCS to
attempt to locate the endpoint through a DNS lookup. It does this by querying the DNS server
configured on the VCS for the location of the domain as per the DNS resolution process.
If the domain part of the URI address was resolved successfully using an H.323 Location SRV
record (i.e. for _ h323ls) then the address returned is queried via an LRQ for the full URI
address.
If the domain part of the URI address was resolved using an H.323 Call SRV record (i.e. for
_ h323cs) or an A/AAAA record lookup then the call is routed directly to the IP address
returned in that record. An exception to this is where the original dial string has a port
specified (e.g. user@example.com:1720) in which case the address returned is queried via
an LRQ for the full URI address.
If the domain part of the URI address was resolved successfully using a SIP SRV record (i.e. for
_ sip) then the request is forwarded to the address returned.
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Configuring Matches for DNS Zones
If you wish locally registered endpoints to be able to place URI calls via the VCS, then at a
minimum you should configure a DNS zone with a match that has a Mode of AlwaysMatch. This
will result in DNS always being queried, but will mean it is queried for all aliases, not just URI
addresses.
To filter the queries sent to the DNS server:
configure a DNS zone with a match that has a Mode of PatternMatch
use the Pattern string and Pattern type fields to define the aliases that will trigger a DNS query.
For example, a match with a Pattern string of *@* and a Pattern type of Regex will mean that DNS
is only queried for aliases in the form of typical URI addresses.
To set up further filters, configure the remaining matches in the same DNS zone. You don’t need
to create new DNS zones unless you want to configure more than the maximum of 5 matches.
You should create separate DNS zones if you want to filter based on the protocol (SIP or H.323) or
hop count to be used.
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