ENUM

From Bizfon Wiki

Purpose

ENUM (see for example http://en.wikipedia.org/wiki/ENUM) is used to locate a service in the Internet by using a telephone number. Typically, this service is voice communication.

There are several ENUM trees available in the Internet. Several countries started ENUM trials with numbers that are publicly available. Therefore, is makes sense to be able to use different ENUM trees apart from the official e164.arpa tree.

There are two problems that need to be addressed with ENUM:

   * Inbound calls must be accepted from any location in the Internet. Things get tricky when the PBX is running more than one domain; then the PBX must locate the right domain. This problem does not only apply to ENUM calls; it applies to all calls that are not coming from a specific location in the Internet. For example, when outside parties are calling SIP URI the PBX faces the same problem. 

   * Outbound calls may go to any location in the Internet. Thanks to the support of DNS NAPTR and DNS SRV, that job is easy for the PBX. However, the dial plan must give a hint to the routing subsystem that the call should be routed using the ENUM rules. 

The PBX supports ENUM by adding a special flag when resolving a SIP URI. If the parameter "enum" is set to "true" while routing a packet, the PBX will apply the RFC 2916 algorithm to the packet.

Setup

First, you need a trunk that is used for routing ENUM requests. This trunk should be a gateway trunk with no outbound proxy set. You may use other features like trunk failover as you like.

If you only want to accept incoming calls, but not use the trunk for outbound calls, then you may set the trunk to "inbound only". On the other hand, if you only want to place outbound calls, then you select "outbound only"; in this case the PBX will not accept any incoming traffic on this trunk.

In order to use this trunk, you need to make a entry into the dial plan. This dial plan must insert the enum parameter in the replacement URI. The domain name of the URI will be used for the ENUM root location. For example, you can use the string "sip:\1@e164.org;enum=true" in the replacement field. It will use the root domain "e164.org".