TANDBERG D14049.01 manual URITextDialinggoeshere, URI Dialing Overview

URITextDialinggoeshere

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About URI Dialing

A URI address typically takes the form name@example.com, 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.

URI Dialing Overview

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.

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.

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.

Introduction	Getting	System	System	H.323 & SIP	Registration	Zones and	Call	Firewall	Bandwidth	Maintenance	Appendices
	Started	Overview	Configuration	Configuration	Control	Neighbors	Processing	Traversal	Control
D 14049.01					81
07.2007