Juha
Heinanen
jh@song.fi
2002
2003
Juha Heinanen
$Revision: 1.2 $
$Date: 2005/08/24 13:24:31 $

# ENUM Module

## Overview

Enum module implements enum_query function that makes an enum query based on the user part of the current Request-URI. The function assumes that the user part consists of an international phone number of the form +decimal-digits, where the number of digits is at least 2 and at most 15. Out of this number `enum_query` forms a domain name, where the digits are in reverse order and separated by dots followed by domain suffix that by default is "e164.arpa.". For example, if the user part is +35831234567, the domain name will be "7.6.5.4.3.2.1.3.8.5.3.e164.arpa.".

After forming the domain name, `enum_query` queries DNS for its NAPTR records. From the possible response `enum_query` chooses those records, whose flags field has string value "u", and whose services field has string value "e2u+[service:]sip" or "e2u+type[:subtype][+type[:subtype]...]" (case is ignored in both cases), and whose regexp field is of the form !pattern!replacement!.

Then `enum_query` sorts the chosen NAPTR records based on their <order, preference>. After sorting, `enum_query` replaces the current Request URI by applying regexp of the most preferred NAPTR record its user part and appends to the request new branches by applying regexp of each remaining NAPTR record to the user part of the current Request URI. If a new URI is a tel URI, `enum_query` appends to it as tel URI parameters the value of tel_uri_params module parameter. Finally, `enum_query` associates a q value with each new URI based on the <order, preference> of the corresponding NAPTR record.

When using `enum_query` without any parameters, it searches for NAPTRs with service type "e2u+sip" in the default enum tree. When using `enum_query` with a single parameter, this parameter will be used as enum tree. When using `enum_query` with two parameters, the functionality depends on the first letter in the second parameter. When the first letter is not a '+' sign, the second parameter will be used to search for NAPTRs with service type "e2u+parameter:sip". When the second parameter starts with a '+' sign, the ENUM lookup also supports compound NAPTRs (e.g. "e2u+voice:sip+video:sip") and searching for multiple service types within one lookup. Multiple service types must be separeted by a '+' sign.

Enum query returns 1 if the current Request URI was replaced and -1 if not.

Enum module also implements is_from_user_e164 function that checks if the user part of from URI is an E164 number.