TANDBERG D14049.01 - Manual (Page 81)

D 14049.01
07.2007 8
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
About URI Dialing
A URI address typically takes the form [email protected] ,
where name is the alias and example.com is the domain.
URI dialing makes use of DNS to enable endpoints registered
with different systems to locate and call each other. With URI
dialing, it is possible to find an endpoint by using DNS to locate
the domain in the URI address and then query that domain for
the alias.
Without URI dialing, you would need to neighbor all the systems
to each other in order for one system to be able to locate an
endpoint registered to another system. This does not scale
well as the number of systems grows. It is also inconvenient
for making one-off calls to endpoints registered with previously
unknown systems.
Endpoints must register with the VCS using a URI address in
order to be reachable using URI dialing.
Enabling URI Dialing via the VCS
URI dialing is enabled separately for outgoing and incoming
calls.
Outgoing Calls
To enable endpoints registered to your VCS to place calls
directly using URI dialing, you must:
configure at least one DNS zone , and
configure at least one DNS Server .
This is described in the section Configuring URI dialing for
outgoing calls .
Incoming Calls
To enable endpoints registered to your VCS to receive calls
directly using URI dialing, you must:
ensure all endpoints are registered with a URI address
configure appropriate DNS records, depending on the
protocols and transport types you wish to use.
This is described in the section Configuring URI dialing for
Incoming calls .
Firewall Traversal Calls
To configure your system so that you can place and receive
calls using URI dialing through a firewall, see the section
URI
Dialing and firewall traversal .
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URI Dialing Overview
URI Dialing
If a DNS zone and/or a DNS server have not been
configured on the local VCS, calls made using URI
dialing could still be placed if the local VCS is
neighbored with another VCS that has been appropriately
configured. Any URI dialed calls will go via the neighbor. This
configuration is useful if you want all URI dialing to be made via
one particular system, e.g. a VCS Border Controller.
URI Resolution Process via DNS
When a system is attempting to locate a destination URI
address using the DNS system, the general process is as
follows:
The system will send a query (via its DNS server) for a
SRV record for the domain in the URL. If available, this
SRV record will return information about the authoritative
gatekeeper (H.323) or proxy (SIP) for that domain (e.g. its
FQDN and listening port).
The system will then send out another query for an A/AAAA
record for the FQDN returned in the SRV record. If available,
this will return the actual IP address of the gatekeeper/
proxy. Once its IP address has been discovered, the system
will query that gatekeeper/proxy for the URI.
If a relevant SRV record cannot be located, the system will
fall back to looking for an A or AAAA record for the domain in
the URL. If such a record is found, the call will be routed to
that IP address. .
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