1. Enumservice VOID draft-stastny-enum-void-00 Richard Stastny Lawrence Conroy IETF60 San Diego

2. August 2004Richard Stastny2 Abstract Registers the 'ENUMservice' 'void' using the URI scheme 'mailto:' This 'ENUMservice' SHALL be used to indicate that the E.164 number or E.164 number range connected to the domain used in DNS as described in RFC3761 is not assigned to –an end-user in case of an E.164 number or –to a communication service provider in case of an E.164 number range.

3. August 2004Richard Stastny3 Current Situation For ENUM, the E.164 number assignee has the exclusive right to register a domain associated with "their" number, and has exclusive control over the content made available in this zone. If an assignee of an E.164 number does not choose to register the associated ENUM domain, then any DNS query on that domain will return a response indicating 'no such domain' (NXDOMAIN, code 3). If no registration exists associated with an E.164 number, then that potential caller (or their agents) have no further information, and drop the call to their default network (e.g. the PSTN), assuming that this will route the call appropriately.

4. August 2004Richard Stastny4 The problem Some NRAs now allocate number ranges for exclusive use of ENUM registrations (e.g. +43780 in Austria). Calls to E.164 numbers in this range MUST be processed using ENUM, and delivered to the URI generated as a result of a successful ENUM query. Such a call CANNOT be simply "dropped" onto the default network for delivery.

5. August 2004Richard Stastny5 The issue The originating user agent is unaware of this choice, may assume to drop the call to the PSTN and the call will fail. So a mechanism "between" a registration holding NAPTRs with URIs and the lack of a domain registration would be useful. As there is no end user as an assignee for an unused number, there cannot be a registration for the associated ENUM domain. It would be useful if the originating end user could receive a response that states "there is no service via this number“.

6. August 2004Richard Stastny6 The proposed solution We propose an explicit indication of this "number unassigned" state. This uses a NAPTR in the "enclosing" zone, with an enumservice called VOID that should be taken as an assertion that the associated E.164 number is not assigned to an end user for communications service; it's an unused number. This NAPTR can also be used by an NRA to indicate number blocks that it has reserved or has not allocated, or has not assigned to a service provider.

7. August 2004Richard Stastny7 The mailto: URI Where a number (or number range) has not been assigned to an end user, there cannot be an associated ENUM registration. Thus there cannot be information made available via ISIS/Whois on the identity of the current "owner" of the number. For this reason, we propose that the VOID indication also includes an email address by which the authority responsible for this number (or range) can be contacted. This may not be the same entity as the one that maintains the DNS service for that "enclosing zone"; often the NRA will sub-contract a Registry Operator to maintain the DNS, but it is the NRA who is the authority for the E.164 number range, not that Registry Operator.

8. August 2004Richard Stastny8 Enumservice VOID Enumservice Name: "void" –Type(s): "void" –Subtype(s): "mailto" –URI Scheme(s): "mailto:" Definition of expected action: –If a NAPTR with this ENUMservice is received, it indicates that the queried E.164 number is currently unassigned to an end user for communications service. –The recipient SHOULD treat this response as if they had received a "number not in service" indication from a terminating network.

9. August 2004Richard Stastny9 Example $ORIGIN 0.6.9.2.3.6.1.4.4.e164.arpa. 8.3.0 NAPTR 10 100 "u" "E2U+void:mailto" "!^.*$!mailto:num-drama-info@ofcom.org.uk!" This indicates that the controller of the number block +441632960xxx does not provide telephony service via the number +441632960038; it is not assigned to an end user.