Enum support in the ENUMLOOKUP dialplan function ------------------------------------------------ 2005-09-06 jtodd@loligo.com The ENUMLOOKUP function is more complex than it first may appear, and this guide is to give a general overview and set of examples that may be well-suited for the advanced user to evaluate in their consideration of ENUM or ENUM-like lookup strategies. This document assumes a familiarity with ENUM (RFC3761) or ENUM-like methods, as well as familiarity with NAPTR DNS records (RFC2915, RFC3401-3404). For an overview of NAPTR records, and the use of NAPTRs in the ENUM global phone-number-to-DNS mapping scheme, please see http://www.voip-info.org/tiki-index.php?page=ENUM for more detail. Using ENUM within Asterisk can be simple or complex, depending on how many failover methods and redundancy procedures you wish to utilize. Implementation of ENUM paths is supposedly defined by the person creating the NAPTR records, but the local administrator may choose to ignore certain NAPTR response methods (URI types) or prefer some over others, which is in contradiction to the RFC. The ENUMLOOKUP method simply provides administrators a method for determining NAPTR results in either the globally unique ENUM (e164.arpa) DNS tree, or in other ENUM-like DNS trees which are not globally unique. The methods to actually create channels ("dial") results given by the ENUMLOOKUP function is then up to the administrator to implement in a way that best suits their environment. Function: ENUMLOOKUP(number[|Method-type[|options[|record#[|zone-suffix]]]]) Performs an ENUM tree lookup on the specified number, method type, and ordinal record offset, and returns one of four different values: 1) post-parsed NAPTR of one method (URI) type 2) count of elements of one method (URI) type 3) count of all method types 4) full URI of method at a particular point in the list of all possible methods Arguments: number = telephone number or search string. Only numeric values within this string are parsed; all other digits are ignored for search, but are re-written during NAPTR regexp expansion. service_type = tel, sip, h323, iax2, mailto, ...[any other string], ALL. Default type is "sip". Special name of "ALL" will create a list of method types across all NAPTR records for the search number, and then put the results in an ordinal list starting with 1. The position specified will then be returned, starting with 1 as the first record (lowest value) in the list. The service types are not hardcoded in Asterisk except for the default (sip) if no other service type specified; any method type string (IANA-approved or not) may be used except for the string "ALL". options = optional specifiers. c = count. Returns the number of records of this type are returned (regardless of order or priority.) If "ALL" is the specified service_type, then a count of all methods will be returned for the DNS record. record# = which record to present if multiple answers are returned = The record in priority/order sequence based on the total count of records passed back by the query. If a service_type is specified, all entries of that type will be sorted into an ordinal list starting with 1 (by order first, then priority). The default of is "1" zone_suffix = allows customization of the ENUM zone. Default is e164.arpa. EXAMPLE USES: Let's use this ENUM list as an example (note that these examples exist in the DNS, and will hopefully remain in place as example destinations, but they may change or become invalid over time. The end result URIs are not guaranteed to actually work, since some of these hostnames or SIP proxies are imaginary. Of course, the tel: replies go to directory assistance for New York City and San Francisco...) Also note that the complex SIP NAPTR at weight 30 will strip off the leading "+" from the dialed string if it exists. This is probably a better NAPTR than hard-coding the number into the NAPTR, and it is included as a more complex regexp example, though other simpler NAPTRs will work just as well. 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 10 100 "u" "E2U+tel" "!^\\+13015611020$!tel:+12125551212!" . 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 21 100 "u" "E2U+tel" "!^\\+13015611020$!tel:+14155551212!" . 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 25 100 "u" "E2U+sip" "!^\\+13015611020$!sip:2203@sip.fox-den.com!" . 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 26 100 "u" "E2U+sip" "!^\\+13015611020$!sip:1234@sip-2.fox-den.com!" . 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 30 100 "u" "E2U+sip" "!^\\+*([^\\*]*)!sip:\\1@sip-3.fox-den.com!" . 0.2.0.1.1.6.5.1.0.3.1.loligo.com. 3600 IN NAPTR 55 100 "u" "E2U+mailto" "!^\\+13015611020$!mailto:jtodd@fox-den.com!" . Example 1: Simplest case, using first SIP return (use all defaults except for domain name) exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,,,,loligo.com)}) returns: ${foo}="2203@sip.fox-den.com" Example 2: What is the first "tel" pointer type for this number? (after sorting by order/preference; default of "1" is assumed in options field) exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,tel,,,loligo.com)}) returns: ${foo}="+12125551212" Example 3: How many "sip" pointer type entries are there for this number? exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,sip,c,,loligo.com)}) returns: ${foo}=3 Example 4: For all the "tel" pointer type entries, what is the second one in the list? (after sorting by preference) exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,tel,,2,loligo.com)}) returns: ${foo}="+14155551212" Example 5: How many NAPTRs (tel, sip, mailto, etc.) are in the list for this number? exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,ALL,c,,loligo.com)}) returns: ${foo}=6 Example 6: Give back the second full URI in the sorted list of all NAPTR URIs: exten => 100,1,Set(foo=${ENUMLOOKUP(+13015611020,ALL,,2,loligo.com)}) returns: ${foo}="tel:+14155551212" [note the "tel:" prefix in the string] Example 7: Look up first SIP entry for the number in the e164.arpa zone (all defaults) exten => 100,1,Set(foo=${ENUMLOOKUP(+437203001721)}) returns: ${foo}="enum-test@sip.nemox.net" [note: this result is subject to change as it is "live" DNS and not under my control] Example 8: Look up the ISN mapping in freenum.org alpha test zone exten => 100,1,Set(foo=${ENUMLOOKUP(1234*256,,,,freenum.org)}) returns: ${foo}="1234@204.91.156.10" [note: this result is subject to change as it is "live" DNS] Example 9: Give back the first SIP pointer for a number in the enum.yoydynelabs.com zone (invalid lookup) exten => 100,1,Set(foo=${ENUMLOOKUP(1234567890,sip,,1,enum.yoyodynelabs.com)}) returns: ${foo}="" Usage notes and subtle features: a) The use of "+" in lookups is confusing, and warrants further explanation. All E.164 numbers ("global phone numbers") by definition need a leading "+" during ENUM lookup. If you neglect to add a leading "+", you may discover that numbers that seem to exist in the DNS aren't getting matched by the system or are returned with a null string result. This is due to the NAPTR reply requiring a "+" in the regular expression matching sequence. Older versions of Asterisk add a "+" from within the code, which may confuse administrators converting to the new function. Please ensure that all ENUM (e164.arpa) lookups contain a leading "+" before lookup, so ensure your lookup includes the leading plus sign. Other DNS trees may or may not require a leading "+" - check before using those trees, as it is possible the parsed NAPTRs will not provide correct results unless you have the correct dialed string. If you get console messages like "WARNING[24907]: enum.c:222 parse_naptr: NAPTR Regex match failed." then it is very possible that the returned NAPTR expects a leading "+" in the search string (or the returned NAPTR is mis-formed.) b) If a query is performed of type "c" ("count") and let's say you get back 5 records and then some seconds later a query is made against record 5 in the list, it may not be the case that the DNS resolver has the same answers as it did a second or two ago - maybe there are only 4 records in the list in the newest query. The resolver should be the canonical storage location for DNS records, since that is the intent of ENUM. However, some obscure future cases may have wildly changing NAPTR records within several seconds. This is a corner case, and probably only worth noting as a very rare circumstance. (note: I do not object to Asterisk's dnsmgr method of locally caching DNS replies, but this method needs to honor the TTL given by the remote zone master. Currently, the ENUMLOOKUP function does not use the dnsmgr method of caching local DNS replies.) c) If you want strict NAPTR value ordering, then it will be necessary to use the "ALL" method to incrementally step through the different returned NAPTR pointers. You will need to use string manipulation to strip off the returned method types, since the results will look like "sip:12125551212" in the returned value. This is a non-trivial task, though it is required in order to have strict RFC compliance and to comply with the desires of the remote party who is presenting NAPTRs in a particular order for a reason. d) Default behavior for the function (even in event of an error) is to move to the next priority, and the result is a null value. Most ENUM lookups are going to be failures, and it is the responsibility of the dialplan administrator to manage error conditions within their dialplan. This is a change from the old app_enumlookup method and it's arbitrary priority jumping based on result type or failure. e) Anything other than digits will be ignored in lookup strings. Example: a search string of "+4372030blah01721" will turn into 1.2.7.1.0.0.3.0.2.7.3.4.e164.arpa. for the lookup. The NAPTR parsing may cause unexpected results if there are strings inside your NAPTR lookups. f) If there exist multiple records with the same weight and order as a result of your query, the function will RANDOMLY select a single NAPTR from those equal results. g) Currently, the function ignores the settings in enum.conf as the search zone name is now specified within the function, and the H323 driver can be chosen by the user via the dialplan. There were no other values in this file, and so it becomes deprecated. h) The function will digest and return NAPTRs which use older (deprecated) style, reversed method strings such as "sip+E2U" instead of the more modern "E2U+sip" i) There is no provision for multi-part methods at this time. If there are multiple NAPTRs with (as an example) a method of "E2U+voice:sip" and then another NAPTR in the same DNS record with a method of ""E2U+sip", the system will treat these both as method "sip" and they will be separate records from the perspective of the function. Of course, if both records point to the same URI and have equal priority/weight (as is often the case) then this will cause no serious difficulty, but it bears mentioning. j) ISN (ITAD Subscriber Number) usage: If the search number is of the form ABC*DEF (where ABC and DEF are at least one numeric digit) then perform an ISN-style lookup where the lookup is manipulated to C.B.A.DEF.domain.tld (all other settings and options apply.) See http://www.freenum.org/ for more details on ISN lookups. In the unlikely event you wish to avoid ISN re-writes, put an "n" as the first digit of the search string - the "n" will be ignored for the search. ==EXAMPLES== All examples below except where noted use "e164.arpa" as the referenced domain, which is the default domain name for ENUMLOOKUP. All numbers are assumed to not have a leading "+" as dialed by the inbound channel, so that character is added where necessary during ENUMLOOKUP function calls. ; example 1 ; ; Assumes North American international dialing (011) prefix. ; Look up the first SIP result and send the call there, otherwise ; send the call out a PRI. This is the most simple possible ; ENUM example, but only uses the first SIP reply in the list of ; NAPTR(s). ; exten => _011.,1,Set(enumresult=${ENUMLOOKUP(+${EXTEN:3})}) exten => _011.,n,Dial(SIP/${enumresult}) exten => _011.,n,Dial(Zap/g1/${EXTEN}) ; ; end example 1 ; example 2 ; ; Assumes North American international dialing (011) prefix. ; Check to see if there are multiple SIP NAPTRs returned by ; the lookup, and dial each in order. If none work (or none ; exist) then send the call out a PRI, group 1. ; exten => _011.,1,Set(sipcount=${ENUMLOOKUP(${EXTEN:3},sip,c)}|counter=0) exten => _011.,n,While($["${counter}"<"${sipcount}"]) exten => _011.,n,Set(counter=$[${counter}+1]) exten => _011.,n,Dial(SIP/${ENUMLOOKUP(+${EXTEN:3},sip,,${counter})}) exten => _011.,n,EndWhile exten => _011.,n,Dial(Zap/g1/${EXTEN}) ; ; end example 2 ; example 3 ; ; This example expects an ${EXTEN} that is an e.164 number (like ; 14102241145 or 437203001721) ; Search through e164.arpa and then also search through e164.org ; to see if there are any valid SIP or IAX termination capabilities. ; If none, send call out via Zap channel 1. ; ; Start first with e164.arpa zone... ; exten => _X.,1,Set(sipcount=${ENUMLOOKUP(+${EXTEN},sip,c)}|counter=0) exten => _X.,2,GotoIf($["${counter}"<"${sipcount}"]?3:6) exten => _X.,3,Set(counter=$[${counter}+1]) exten => _X.,4,Dial(SIP/${ENUMLOOKUP(+${EXTEN},sip,,${counter})}) exten => _X.,5,GotoIf($["${counter}"<"${sipcount}"]?3:6) ; exten => _X.,6,Set(iaxcount=${ENUMLOOKUP(+${EXTEN},iax2,c)}|counter=0) exten => _X.,7,GotoIf($["${counter}"<"${iaxcount}"]?8:11) exten => _X.,8,Set(counter=$[${counter}+1]) exten => _X.,9,Dial(IAX2/${ENUMLOOKUP(+${EXTEN},iax2,,${counter})}) exten => _X.,10,GotoIf($["${counter}"<"${iaxcount}"]?8:11) ; exten => _X.,11,NoOp("No valid entries in e164.arpa for ${EXTEN} - checking in e164.org") ; ; ...then also try e164.org, and look for SIP and IAX NAPTRs... ; exten => _X.,12,Set(sipcount=${ENUMLOOKUP(+${EXTEN},sip,c,,e164.org)}|counter=0) exten => _X.,13,GotoIf($["${counter}"<"${sipcount}"]?14:17) exten => _X.,14,Set(counter=$[${counter}+1]) exten => _X.,15,Dial(SIP/${ENUMLOOKUP(+${EXTEN},sip,,${counter},e164.org)}) exten => _X.,16,GotoIf($["${counter}"<"${sipcount}"]?14:17) ; exten => _X.,17,Set(iaxcount=${ENUMLOOKUP(+${EXTEN},iax2,c,,e164.org)}|counter=0) exten => _X.,18,GotoIf($["${counter}"<"${iaxcount}"]?19:22) exten => _X.,19,Set(counter=$[${counter}+1]) exten => _X.,20,Dial(IAX2/${ENUMLOOKUP(+${EXTEN},iax2,,${counter},e164.org)}) exten => _X.,21,GotoIf($["${counter}"<"${iaxcount}"]?19:22) ; ; ...then send out PRI. ; exten => _X.,22,NoOp("No valid entries in e164.org for ${EXTEN} - sending out via Zap") exten => _X.,23,Dial(Zap/g1/${EXTEN}) ; ; end example 3