Internet Draft Richard Shockey Expires June 2000 Shockey Consulting LLC INFORMATIONAL December 9, 1999 The use of DNS based e164 Resolution Services by Internet Fax Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet Drafts as reference material or to cite them other than as a "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the"1id- abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. This Internet-Draft is in conformance with Section 10 of RFC2026. Overview Work has begun within the IETF ENUM Work Group to define a DNS based service for mapping an e164 telephone number to a single or set of Internet resources associated with that number. This service may offer solutions to a number of difficulties associated with Internet Fax as defined by RFC 2305, RFC 2532 and other existing or emerging standards such as ITU T.38 or the Internet Print Protocol. Shockey Expires June 2000 Page 1 Internet Draft E164 DNS and Internet Fax December 1999 This document is offered as INFORMATIONAL only. 1. ABSTRACT There has been substantial work within the IETF to define Internet Fax services based on an SMTP based store and forward model. This transmission model has imposed some limitations of the quality and type of content transmitted. A secondary issue with email based Internet fax is the inherent difficulty of ascertaining the capabilities of a recipient in advance of sending. Additional work with the ITU has defined a real time fax standard [T.38] based on the transmission of classic T.30 frame and data information within a H.323 session. Typical fax terminal devices or multifunction peripherals with fax capability are relatively compact in size. There is often insufficient space on the device to accommodate an ergonomically correct keyboard necessary to enter an e-mail address or other URL's, however 12 button numeric telephony keypads on fax devices are universal. Emerging classes of fax terminal devices, multifunction peripherals are multi-modal as well, meaning that they can send and receive facsimile messages either over the General Switched Telephone Network or a variety Internet services. Telephone numbers are natural identifiers for devices or endpoints capable of sending and receiving facsimile messages. It is therefore useful to explore how clients and devices might discover via some form of directory,Internet based facsimile resources based on existing e164 numbers. 2. THE E164 RESOLUTION SERVICE The Internet Domain Name System provides an ideal technology for this directory due to it's fast, hierarchical structure and distributed administrative model. Earlier experimentation with the TPC.INT [TPC1] remote printing experiment has shown how the hierarchical assignment of telephone numbers can be mapped directly to the hierarchy of domains within the DNS. Work on a DNS based the E164 resolution model is being undertaken in the IETF ENUM Work Group [E164RES][E164RQMTS]. Shockey Expires June 2000 Page 2 Internet Draft E164 DNS and Internet Fax December 1999 Its potential use in Voice Mail systems is described in several documents listed in the appendix of this document [VPIMARS] [VPIMLDAP]. 3. INTERNET FAX CALL MODEL USING E164 RESOLUTION The fundamental assumption of this call model is that Internet Fax devices or clients would, given a phone number, first execute a DNS query of the before any transmission or call setup to determine the preferred mode of transmission by the recipient. 3.1 DNS QUERY The remainder of this section describes how this scheme may be used in the context of Internet Fax. A full description of this technique is described in [E164RES]. A typical fully qualified e164 fax number in typical use in North American (1 314 918-9015) is translated into a DNS query based on reversing the order of the digits in the phone number and placing dots in between, to make delegation of numbers possible in the DNS. Example: (where 1 is the NANP Country Code) 3.2 USAGE EXAMPLES Example 1: Once the number has been suitably prepared for DNS query, the facsimile device then executes a DNS query to the NAPTR [NAPTR] record within the DNS entry for (5.1.0.9.8.1.9.4.1.3.1.e164.int) and a response is generated such as the following: IN NAPTR 10 10 "a" "ifax+N2R" "" "mailto:rshockey@ix.netcom.com". IN NAPTR 102 10 "s" "faxcall+N2R" "" _potscall._phoneco.net. The result of this query is to define a preference that the fax should be sent by email due to the low order preference field [10] and the service defined ["ifax+N2R"] to a destination mailto: URI (the "a" flag in the NAPTR record). The second part of the response indicates that a traditional fax call may also be used but its priority is lower due to the higher preference field [102]. As an example, classic fax service is defined by ["faxcall+N2R"]. The record "potscall" is a placeholder. DNS would return the e164 record number normally as part of the response. Shockey Expires June 2000 Page 3 Internet Draft E164 DNS and Internet Fax December 1999 The fax device would then transmit the fax to the email address indicated using the rules defined for Internet Fax in [RFC 2305]. No GSTN T.30 fax transaction would take place unless the SMTP service was discovered to be unavailable. Example 2: A more complex query response might indicate a rank ordering of preferences by the recipient. IN NAPTR 10 10 "a" "T38+N2R" "" "t38:faxserver.mydomain.com". IN NAPTR 100 10 "a" "ifax+N2R" "" "mailto:rshockey@ix.netcom.com". IN NAPTR 200 10 "s" "faxcall+N2R" "" _potscall._mydomain.net. In this case the preferred method is T.38 (preference 10) as indicated in the NAPTR service field, with alternatives being IFAX (preference 100) and traditional fax telephone call (preference 200). It is then the sender's task to determine the best available method of transmission. Various forms of fax transmission services would need to be registered as valid NAPTR services fields with IANA to facilitate this process. Possible service records would include: T.30 GSTNfax = "faxcall" T.38 Realtine = "T38" IFAX RFC 2305 = "ifax EIFAX RFC = "eifax" IPP = "ipp" Example 3: IN NAPTR 10 10 "a" "ipp+N2R" "" "ipp:ipp.printer3.mydomain.com". IN NAPTR 100 10 "a" "ifax+N2R" "" "mailto:faxmachine@mydomain.com". IN NAPTR 200 10 "s" "faxcall+N2R" "" _potscall._mydomain.net. In this example the preferred method of reception uses the Internet Print Protocol and E-Mail and T.30 fax are secondary options. 4. ADDRESS CAPABILITIES QUERY A problem for fax transmissions based on SMTP is determining the capabilities of the recipient in advance of sending the document. Internet Fax [RFC 2305, RFC 2532] outline such a requirement without actually suggesting how it should be accomplished. Shockey Expires June 2000 Page 4 Internet Draft E164 DNS and Internet Fax December 1999 New IETF work within RESCAP may provide one way to do this. The DNS phone number mapping scheme described above might also provide an additional URL, perhaps in the form of a SRV record that could be accessed for determination of recipient capabilities. 5. REFERENCES [DNS1] Mockapetris, P., "Domain names - implementation and specification", RFC1035, Nov 1987. [DNS2] Mockapetris, P., "Domain names - concepts and facilities", RFC 1034, Nov 1987. [E164] CCITT Recommendation E.164 (1991), Telephone Network and ISDN Operation, Numbering, Routing and Mobile Service - Numbering Plan for the ISDN Era. [E164RES] Falstrom, Patrik, "E.164 Number and DNS" draft-faltstron-e164- xx.txt, work-in progress [E164RQMTS] Brown, A., "ENUM Requirements", draft-ietf-enum-rqmts-xx.txt" work-in-progress. [IFAX] [RFC2305] K.Toyoda, H. Ohno, J. Murai, D. Wing, "A Simple Mode of Facsimile Using Internet Mail", RFC 2305, March 1998. [TPC1] Malamud, Carl, Rose, Marshall, "Principles of Operation for the TPC.INT Subdomain: Remote Printing -- Technical Procedures", RFC 1530, October 1993. [T.38] ITU-T, "Procedures for real time Group 3 facsimile communications over IP networks"" ITU-T Recommendation T.38, July 1998 [NAPTR] Mealing,M., Daniel,R., "The Naming Authority Pointer (NAPTR) DNS Resource Record", draft-ietf-urn-naptr-rr-xx.txt, work-in-progress [VPIMARS] Vaudreuil, Greg, "Voice Messaging Directory Service: DNS-based", work-in-progress. [VPIMLDAP] Vaudreuil, Greg, " Voice Messaging Directory Service: Address Validation Schema", work-in-progress. [SRV] Gulbrandsen, A., Vixie, P., "A DNS RR for specifying the location of services (DNS SRV)", RFC 2052, October 1996. Shockey Expires June 2000 Page 5 Internet Draft E164 DNS and Internet Fax December 1999 6. ACKNOWLEDGMENTS This document shamelessly and without remorse, swipes text and concepts from the work of Patrik Falstrom and Greg Vandreuil. Thanks to Graham Klyne for suggestions and comments. 7. AUTHORS' ADDRESSES Richard Shockey Shockey Consulting LLC 8045 Big Bend Blvd. Suite 110 St. Louis, MO 63119 Voice 314.918.9020 Fax to EMail 815.333.1237 (Preferred for Fax) INTERNET Mail & IFAX : rshockey@ix.netcom.com GSTN Fax 314.918.9015 8. COPYRIGHT NOTICE "Copyright (C) The Internet Society (1998). All Rights Reserved. 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