Enum Module

Enum module implements [i_]enum_query functions that make an enum query based on the user part of the current Request-URI. These functions assume 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.”. i_enum_query operates in a similar fashion. The only difference is that it adds a label (default "i") to branch off from the default, user-ENUM tree to an infrastructure ENUM tree.

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.

Most of the time you want to route based on the RURI. On rare occasions you may wish to route based on something else. The function enum_pv_query mimics the behavior of the enum_query function except the E.164 number in its pseudo variable argument is used for the enum lookup instead of the user part of the RURI. Obviously the user part of the RURI is still used in the NAPTR regexp.

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

In addition to standard ENUM, support for ISN (ITAD Subscriber Numbers) is provided as well. To allow ISN lookups to resolve, a different formatting algorithm is expected by the DNS server. Whereas a ENUM NAPTR record expects a DNS query of the form 9.8.7.6.5.4.3.2.1.suffix, ISN method expects a DNS query of the form 6.5.1212.suffix. That is, a valid ISN number includes a prefix of '56' in the example. The rest of the number is a ITAD (Internet Telephony Administrative Domain) as defined in RFCs 3872 and 2871, and as allocated by the IANA in http://www.iana.org/assignments/trip-parameters. The ITAD is left intact and not refersed as ENUM requires. To learn more about ISN please refer to documents at www.freenum.org.

To complete a ISN lookup on the user part of the Request-URI, isn_query() is used instead of enum_query().

Enum module also implements is_from_user_enum function. This function does an enum lookup on the from user and returns true if found, false otherwise.

The module depends on the following modules (in the other words the listed modules must be loaded before this module):