Internet DRAFT - draft-ietf-fax-faxaddr-v2
draft-ietf-fax-faxaddr-v2
Network Working C. Allocchio
Group GARR-Italy
INTERNET-DRAFT June 2001
Obsoletes: RFC2304 Expires: December 2001
Updates: RFC2846 File: draft-ietf-fax-faxaddr-v2-04.txt
Minimal FAX address format in Internet Mail
Status of this Memo
This document is an Internet Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Important Note for the RFC Editor:
Within this document all references and occurences given as
"RFC2303bis" need to be replaced by "RFCxxxx", where "xxxx" is
the number which will be assigned to draft-ietf-fax-minaddr-v2-03.txt
and all references and occurences given as "RFC2304bis" need to
be replaced by "RFCyyyy", where "yyyy" is the number which will be
assigned to THIS documnt.
Abstract
This memo describes a simple method of encoding GSTN addresses of
facsimile devices in the local-part of Internet email addresses.
As with all Internet mail addresses, the left-hand-side (local- part)
of an address generated according to this specification, is not to be
interpreted except by the MTA that is named on the right-hand-side
(domain).
1. Introduction
Since the very first e-mail to fax gateway objects appeared, a
number of different methods to specify a fax address as an e-mail
address have been used by implementors. Several objectives for this
methods have been identified, like to enable an e-mail user to send
and receive faxes from his/her e-mail interface, to allow some kind of
"fax over e-mail service" transport (possibly reducing the costs of
GSTN long distance transmissions) while using the existing e-mail
infrastructure.
This memo describes the MINIMAL addressing method and standard
extensions to encode FAX addresses into e-mail addresses, as required
in reference [13]. The opposite problem, i.e. to allow a traditional
numeric-only fax device user to access the e-mail transport service,
is not discussed here.
This IANA forms used to register the standard elements defined here
are given in the "IANA Considerations" chapter (section 7 of this
document).
All implementations supporting FAX over e-mail address format MUST
support this minimal specification.
1.1 Terminology and Syntax conventions
In this document the formal definitions are described using ABNF
syntax, as defined into [7]. We will also use some of the "CORE
DEFINITIONS" defined in "APPENDIX A - CORE" of that document. The
exact meaning of the capitalised words
"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
"SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL"
is defined in reference [6].
In this document the following new terms are also defined:
I-fax device:
an I-pstn device type [13] which is able to communicate either
directly or indirectly with the traditional FAX over GSTN
service;
mta-I-fax:
the Internet domain name which identifies uniquely an I-fax
device over the Internet (see also mta-I-pstn in [13]);
fax-email:
the complete Internet e-mail address structure which is used to
transport a FAX address over the Internet e-mail service (see
also pstn-email in [13]).
2. Minimal Fax address
The minimal fax address within e-mail has been defined for consistency
with reference [13] and it contains two elements: the fax-mbox and
an optional qualif-type1 element.
More precisely the GSTN minimal address specification requires the
use of a unique service-selector for each specific application
(section 2 in [13]).
The "service-selector" defined for the fax service is as follows:
service-selector = "FAX"
In the syntax for the fax address a qualif-type1 element has been
defined for support of T.30/T.33 subaddresses (see section 2 of [13]).
The use of this element is OPTIONAL, but compliant implementations
MUST be able to support and correctly interpret it when present.
Its definition is as follows:
qualif-type1 = "/" t33-sep "=" sub-addr
where
t33-sep = "T33S"
sub-addr = 1*( DIGIT )
Thus, the minimal specification of a fax in e-mail address is:
fax-address = fax-mbox [ "/T33S=" sub-addr ]
fax-mbox = "FAX=" global-phone
Notes:
For the case of a single subaddress, only numbers are allowed in
<sub-addr> which is consistent with T.30, T.33, and this document.
While T.30 and T.33 use SPACE to pad its field, padding isn't necessary
in the <sub-addr> field defined by this document.
For the case of multiple subaddresses, T.33 specifies the "#"
character be used to specify multiple subaddreses. However,
only digits are permitted in the <sub-addr> field defined by this
document. Refer to section 4.1 in case multiple <sub-addr> per
per <fax-mbox> need to be specified.
The Minimal supported syntax for global-phone (as described in
section 2.1 of reference [13]) is:
global-phone = "+" 1*( DIGIT / written-sep )
written-sep = ( "-" / "." )
Refer to section 2.1 in [13] for other important considerations about
the global-phone element.
2.2 Some examples of a minimal "fax-address"
Some examples of minimal fax-address follows:
FAX=+3940226338
FAX=+12027653000/T33S=1387
FAX=+33-1-88335215
Note:
the examples shown are just for illustration purpouses.
3. The e-mail address of the I-fax device: mta-I-fax
An "I-fax device" has, among its characteristics, a unique
Internet domain name which identifies it on the Internet. Within
Internet mail, this is the Right Hand Side (RHS) part of the
address, i.e. the part on the right of the "@" sign. For purpouses
of this document we will call this "mta-I-fax"
mta-I-fax = domain
For "domain" strings used in SMTP transmissions, the string MUST
conform to the requirements of that standard's <domain>
specifications [1], [3]. For "domain" strings used in message
content headers, the string MUST conform to the requirements of the
relevant standards [2], [3].
Note: the use of "domain names" or "domain literals"
is permitted in addresses in both the SMTP envelope
and message header fields.
4. The fax-email
The complete structure used to transfer a minimal FAX address over
the Internet e-mail transport system is called "fax-email". This
object is a an e-mail address which conforms to [2] and [3]
"addr-spec" syntax, with structure refinements which allows the
FAX number to be identified.
fax-email = ["""] ["/"] fax-address ["/"] ["""] "@" mta-I-fax
Implementors' note:
The optional "/" characters can result from translations from
other transport gateways (such as some X.400 gateways) which
have included the "/" as an optional element. Implementations
MUST accept the optional slashes but SHOULD NOT generate them.
Gateways are allowed to strip them off when converting to
Internet mail addressing. The relevant standard [2], [3] define
exactly when the optional "quotes" characters surrounding the
entire local part (i.e. the part on the left of the "@" character
into the fax-email) MUST be added.
4.1 Multiple subaddresses
There are some instances in GSTN applications where multiple
subaddresses are used: T.33 subaddresses in fax service are one of
these cases. In e-mail practice a separate and unique e-mail
address is always used for each recipient; as such, if multiple T.33
subaddresses are present, the use of multiple "fax-email" elements
is REQUIRED.
Implementors' note:
The UA MAY accept multiple subaddress elements for the same
global-phone, but it MUST generate multiple "fax-mbox" elements
when submitting the message to the MTA.
4.2 Some examples of minimal "fax-email"
Some examples of minimal fax-email addresses follows:
FAX=+3940226338@faxworld.org
FAX=+12027653000/T33S=1387@faxworld.org
/FAX=+33-1-88335215/@faxworld.org
Note:
the examples shown are just for illustration purpouses.
5. Conclusion
This proposal creates a minimal standard encoding for FAX addresses
within the global e-mail transport system. The proposal is consistent
with existing e-mail standards.
6. Security Considerations
This document specifies a means by which FAX addresses can be
encoded into e-mail addresses. Since e-mail routing is determined by
Domain Name System (DNS) data, a successful attack to DNS could
disseminate tampered information, which causes e-mail messages to be
diverted via some MTA or Gateway where the security of the software
has been comprimised.
There are several means by which an attacker might be able to deliver
incorrect mail routing information to a client. These include: (a)
compromise of a DNS server, (b) generating a counterfeit response to
a client's DNS query, (c) returning incorrect "additional
information" in response to an unrelated query. Clients SHOULD ensure
that mail routing is based only on authoritative answers. Once DNS
Security mechanisms [5] become more widely deployed, clients SHOULD
employ those mechanisms to verify the authenticity and integrity of
mail routing records.
7. IANA Considerations
The IANA registration forms for "FAX" service-selector and "T33S"
qualif-type1 elements are defined here. These forms update the
previous registration forms defined in [15].
7.1 IANA Registration form for updated value of GSTN
address service-selector "FAX"
To: IANA@iana.org
Subject: Registration of updated values for the GSTN address
service-selector specifier "FAX"
service-selector name:
FAX
Description of Use:
FAX - specify that the GSTN address refers either to an
Internet Fax device, or an onramp/offramp Fax gateway.
For a complete description refer to RFC2304bis and RFC2303bis
Security Considerations:
See the Security Consideration section of RFC2304bis.
Person & email address to contact for further information:
Claudio Allocchio
INFN-GARR
c/o Sincrotrone Trieste
SS 14 Km 163.5 Basovizza
I 34012 Trieste
Italy
RFC2822: Claudio.Allocchio@garr.it
X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
Phone: +39 040 3758523
Fax: +39 040 3758565
7.2 IANA Registration form for updated value of GSTN
address qualit-type1 keyword "T33S" and value
To: IANA@iana.org
Subject: Registration of updated values for the GSTN address
qualif-type1 element "T33S"
qualif-type1 "keyword" name:
T33S
qualif-type1 "value" ABNF definition:
sub-addr = 1*( DIGIT )
Description of Use:
T33S is used to specify the numeric only optional fax sub-address
element described in "ITU T.33 - Facsimile routing utilizing the
subaddress; recommendation T.33 (July, 1996)". Further detailed
description is available in RFC2304.
Use Restriction:
The use of "T33S" is restricted to "FAX" service-selector, is it has
no meaning outside the fax service.
Security Considerations:
See the Security Consideration section of RFC2304bis.
Person & email address to contact for further information:
Claudio Allocchio
INFN-GARR
c/o Sincrotrone Trieste
SS 14 Km 163.5 Basovizza
I 34012 Trieste
Italy
RFC2822: Claudio.Allocchio@garr.it
X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
Phone: +39 040 3758523
Fax: +39 040 3758565
8. Changes since RFC2304 specification
Although there are no major or technical changes from RFC2304
specification, this section briefly describes where updates and
clarifications were introduced:
- considering the case that telephony systems do not conform any
more to the "single/few" Public Operator paradigm, the old
definition "PSTN - Public Switched Telephone Network" was changed
into the more adequate "GSTN - Global Switched Telephone Network"
one. However, in order to remain consistent with the previous
specification, the ABNF variables names were not changed.
- section 7 "IANA Considerations" and the IANA registration forms
for the "FAX" "service-selector" and for the "T33S" "qualif-type1"
elements were added;
- an explicit list of "new terms" with explanations was added to
section 1.1;
- the case when multiple T.33 subaddresses are present was
described more explicitly in order to clarify how to handle them
(section 4.1);
- in section 3 the language describing "mta-I-fax" was updated to
better describe its relationship with an Internet Mail address;
- in section 4. the quoting rules of the "fax-address" and their
practical use was made explicit both in the definition of
"fax-email" and in the Implementors' note;
- the Author's Address was updated;
- the References list was updates to substitute RFC821 with RFC2821,
RFC822 with RFC2822 and ITU E.164 (1991) with ITU E.164 (1997),
respectiviely.
9. Author's Address
Claudio Allocchio
INFN-GARR
c/o Sincrotrone Trieste
SS 14 Km 163.5 Basovizza
I 34012 Trieste
Italy
RFC2822: Claudio.Allocchio@garr.it
X.400: C=it;A=garr;P=garr;S=Allocchio;G=Claudio;
Phone: +39 040 3758523
Fax: +39 040 3758565
10. References
[1] Klensin, J., "Simple Mail Transfer Protocol", STD 10, RFC 2821,
April 2001.
[2] Resnick, P., " Internet Message Format", STD 11, RFC 2822,
April 2001.
[3] Braden, R., "Requirements for Internet hosts - application and
support", RFC 1123, October 1989.
[4] Malamud, C. and M. Rose, "Principles of Operation for the
TPC.INT Subdomain: Remote Printing -- Technical Procedures", RFC
1528, October 1993.
[5] Eastlake, D. and C. Kaufman, "Domain Name System Security
Extensions", RFC 2065, January 1997.
[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications", RFC 2234, November 1997.
[8] ITU F.401 - Message Handling Services: Naming and Addressing for
Public Message Handling Service; recommendation F.401 (August
1992)
[9] ITU F.423 - Message Handling Services: Intercommunication
Between the Interpersonal Messaging Service and the Telefax
Service; recommendation F.423 (August 1992)
[10] ITU E.164 - The International Public Telecommunication Numbering
Plan E.164/I.331 (May 1997)
[11] ITU T.33 - Facsimile routing utilizing the subaddress;
recommendation T.33 (July, 1996)
[12] ETSI I-ETS 300,380 - Universal Personal Telecommunication
(UPT): Access Devices Dual Tone Multi Frequency (DTMF) sender
for acoustical coupling to the microphone of a handset telephone
(March 1995)
[13] Allocchio, C., "Minimal GSTN address format in Internet Mail",
RFC 2303bis, xxxx 2001.
[14] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay): Mapping
between X.400 and RFC 822/MIME", RFC 2156, January 1998.
[15] Allocchio, C. "GSTN address element extensions in e-mail
services", RFC 2846, June 2000.
11. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
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