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

                 <draft-shockey-e164toifax-00.txt>


Status of this Memo

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provisions of Section 10 of RFC2026.

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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.


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This document is offered as INFORMATIONAL only.

. 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.

. 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].


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Its potential use in Voice Mail systems is described in several documents
listed in the appendix of this document [VPIMARS] [VPIMLDAP].


. 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.


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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.

. 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.



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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.

. 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.


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. 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.

. AUTHORS' ADDRESSES

Richard Shockey
Shockey Consulting LLC
 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

. COPYRIGHT NOTICE

"Copyright (C) The Internet Society (1998). All Rights Reserved.

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The limited permissions granted above are perpetual and will not be
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
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     Vaudreuil, Parsons       Expires 5/1/00                   [Page 12]