- From: Claudio Allocchio <Claudio.Allocchio@garr.it>
- Date: Fri, 22 Feb 2002 10:36:09 +0100
- To: internet-drafts@ietf.org
- cc: ietf-fax@imc.org, discuss@apps.ietf.org, enum@ietf.org, ietf@ietf.org
- Message-ID: <Pine.VMS.3.91-B.1020222102732.9654A-200000@SYNX02.elettra.trieste.it>
Hallo, here is the updated version of DRAFT-ALLOCCHIO-GSTN-02.TXT, which includes, as the only difference from the previous one, an "implementer's note" regarding 'pause' and 'tonewait' which was suggested as helpful. As mentioned in the first release of the draft, "the intention for this document is to provide a unique syntax for Dial Sequences, including expecially phone numbers as a subset. The definitions contained in the draft actually come from existing Draft Standard and Proposed Standard specifications, but were collected here to provide a quick, easy and unique reference document for anybody needing this particualr encoding. The original idea comes from the Application Area Directors, and I made the collection and edited the I-D." I kindly invite you to provide me your comments and suggestions! Thank you all, and regards! Claudio Allocchio ietf fax wg co-chair
Network Working C. Allocchio
Group GARR-Italy
INTERNET-DRAFT February 2002
Expires: August 2002
File: draft-allocchio-gstn-02.txt
Text string notation for Dial Sequences and GSTN / E.164 addresses
Status of this Memo
This document is an Internet Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This memo describes the full set of notations needed to represent
in a text string a Dial Sequence. A Dial Sequence is normally
composed by Dual Tone Multi Frequency (DTMF) elements [1] plus
separators and the additional "actions" (such as "wait for
dialtone", "pause for N secs", etc.) which could be needed to
successfully establish the connection with the target service:
this includes the cases where subaddresses or DTMF menu navigation
apply. Global Switched Telephone Numbers (GSTN) / E.164 addresses
(commonly called "telephone numbers") [2] are a subset of a Dial
Sequence, and thus use the same set of notations.
This notation MUST be used in all specifications needing a text
string representation of a Dial Sequence (including GSTN / E.164
addresses).
1. Introduction
Since the very first devices interacting with GSTN services appeared,
a need for a unique text string representation of telephone numbers,
and more generally DTMF sequences and actions, was forseen.
This memo describes the full text string representation method. The
main scope is thus to provide a unique and complete reference for all
specification needing this representation.
Compatibility with existing Standard Track specifications (such as
[3] [4] [5] [6]) is also one of the most important issues in this
specification.
1.1 Terminology and Syntax conventions
In this document the formal definitions are described using ABNF
syntax, as defined into [7]. This memo also uses 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 [8].
In this document the following terms are also defined:
Dial Sequence:
a series of DTMF elements and human or device "actions";
phone-string:
a text representation of a Dial Sequence;
gstn-phone:
a text representation of a GSTN address (which includes
the E.164 addresses);
subaddr-string:
a text representation of a GSTN subaddress (which includes
ISDN subaddresses [2] and T.33 subaddresses [9]);
post-dial:
a text representation of a post dialling sequence.
2. The "Dial Sequence" definition
The possible elements composing a Dial Sequence can vary from a
minimum number up to a really large and complex collection: in
fact, already the sequences needed to dial a GSTN address, which is
a subset of the generic Dial Sequence, well represents this variety
and complexity of cases.
In particular, a Dial Sequence is composed by:
- "DTMF elelments": normally available as "keys" on numeric keypads
of dialling devices;
- "actions": normally performed by the agent (human or device)
composing the Dial Sequence;
- "separators": used only to improve human readibility of a Dial
Sequence.
2.1 The "phone-string" definition
The text representation of the Dial Sequence elements is defined
into the phone-string specification:
phone-string = 1*( DTMF / pause / tonewait / written-sep )
DTMF = ( DIGIT / "#" / "*" / "A" / "B" / "C" / "D" )
; special DTMF codes like "*", "#", "A", "B",
; "C", "D" are defined in [1].
; Important Note: these elements only apply for
; alphabetic strings used in DTMF operations.
; They are NOT applicable for the alphabetic
; characters that are mapped to digits on phone
; keypads in some countries.
pause = "p"
tonewait = "w"
written-sep = ( "-" / "." )
Note:
DTMF are the "DTMF elements", pause and tonewait are the "actions"
and written-sep is the "separators".
The "pause" and "tonewait" elements interpretation in phone-string
depends on the specific devices and implementation using the
specification. Thus their exact meaning is not defined here as part
of this specification. The implementer's note below gives anyhow
some recommendations drown from common practice. Both "pause" and
"tonewait" are case insensitive.
Implementer's note:
- one instance of a "pause" is recommended to be interpreted as
a pause of one second between the preceding and succeeding dial
string element;
- a "tonewait" is recommended to be interpreted as a pause that
will last until the calling party hears a dial tone or another
indication that more dial string characters may be processed.
An off-hook indication may also be interpreted as this kind of
indication (meaning that the audio channel has been opened to
the receiving party);
- because these characters are not a part of the GSTN subscriber
address (telephone number) per se, any dial string characters
that succeed either a "pause" or "tonewait" should be sent using
DTMF signalling.
The use of written-sep elements is allowed in order to improve
human readibility of phone-string. The written-sep are elements
which can be placed between dial elements such as digits etc.
Any occurences of written-sep elements in a phone-string MUST NOT
result in any action. Conformant implementations MAY drop or
insert written-sep into the phone-string they handle.
The phone-string definition is used in the following sections to
explicitly describe the encoding of some specific subcases where
it applies.
3. The "gstn-phone" definition
In order to access a GSTN address, a human or a device must perform
a Dial Sequence. Thus also a GSTN address can be represented using
the phone-string elements. In particual, standard E.164 numeric
addresses [2] represent a limited subset of all possible GSTN
addresses, while the complete complex case needs a full encoding
schema.
In order to describe this distinction and provide anyhow a complete
encoding schema, the following definition of "gstn-phone" is provided:
gstn-phone = ( global-phone / local-phone )
3.1 The "global-phone" definition
The purpose of global-phone element is to represent standard E.164
numeric addresses. As such it uses a subset of phone-string
definition, only.
The syntax for global-phone element is as follows:
global-phone = "+" 1*( DIGIT / written-sep )
Any other dialling schemes MUST NOT use the leading "+" defined here.
The "+" sign is strictly reserved for the standard "global-phone"
syntax, and, even if not specifically part of phone-string definition,
is needed to label uniquely a global-phone.
3.2 The "local-phone" definition
The local-phone element is intended to represent the set of possible
cases where the global-phone numbering schema does not apply. Given
the different and complex conventions currently being used in the
GSTN system, the local-phone definition supports a large number of
elements.
The detailed syntax for local-phone elements follows:
local-phone = [ exit-code ] dial-number
local-phone =/ exit-code [ dial-number ]
exit-code = phone-string
; this will include elements such as the digit to
; access outside line, the long distance carrier
; access code, the access password to the service,
; etc...
dial-number = phone-string
; this is in many cases composed of different elements
; such as the local phone number, the area code
; (if needed), the international country code
; (if needed), etc...
Notes:
the "+" character is reserved for use in global-phone and MUST NOT
be used in a local-phone string;
please note that a local-phone string MUST NOT be a null string,
i.e. at least an exit-code, or a dial-number or both MUST be
present.
4. The "subaddr-string" definition
In GSTN service there are cases where a subaddress is required to
specify the final destination. To specify these subaddresses a Dial
Sequence is also used, and thus the "subaddr-string" can be encoded
as:
subaddr-string = phone-string
Note:
within actual uses of subaddresses, some specific services can
limit the possible set of phone-string elements allowed. In
particular there are ISDN subaddresses [2] [5], which restrict the
phone-string elements to 1*( DIGIT / written-sep ) and service
specific subaddresses, like the fax service T.33 subaddress [9]
[4] which restrict phone-string elements to 1*( DIGIT ).
5. The "post-dial" definition
In some cases, after the connection with the destination GSTN device
has been established, a further dialling sequence is required to
access further services. A typical example is an automated menu-
driven service using DTMF sequences. These cases may be represented
using "post-dial" definition below:
post-dial = phone-string
6. Examples
In order to clarify the specification we present here a limited set
of examples. Please note that all the examples are for illustration
purpouses, only.
A GSTN address in Italy, dialled from U.S.A., using local-phone,
without written-sep:
01139040226338
A GSTN address address in Germany, using global-phone and
written-sep ".":
+49.81.7856345
A GSTN address in U.S.A. using global-phone and written-sep "-":
+1-202-455-7622
A post-dial sequence, pausing, dialling 1, waiting for dial tone,
dialling 7005393, waiting again for dial tone and dialling 373;
note the use of four "p" elements (pppp) to specify a longer initial
pause:
pppp1w7005393w373
A Dial Sequence in Italy (long distance call), using local-phone,
with exit-code "9", long distant access "0", area code "40",
pause "p" and written-sep ".":
9p040p22.63.38
A Dial Sequence using exit-code "0", a wait for dial tone,
local-phone for an International "800" toll-free number dialled
from Beglium (international prefix "00"), and a post-dial sequence
to access a voice mailbox with userID "334422" and Personal
Identification Number (PIN) code "1234":
0w00800-39380023pp334422p1234
7. Conclusions
This proposal creates a full standard text encoding for Dial
Sequences, including GSTN / E.164 addresses, and thus provides a
unique common representation method both for standard protocols
and applications.
Some definitions, like these corresponding to an alias of the generic
phone-string element, are somewhat a theoretical distinction; however
they are useful to provide a more subtle distinction, allowing other
specifications to be more exact in a consistent way, too.
The proposal is consistent with existing standard specifications.
8. Security Considerations
This document specifies a means to represent Dial Sequences, which
thus could include GSTN addresses, and private codes sequences,
like Personal Identification Numbers, to access special services.
As these text strings could be transmitted without encoding inside
protocols or applications services, this could allow unauthorized
people to gain access to these codes. Users SHOULD be provided methods
to prevent this disclosure, like code encryption, or masquerading
techniques: out-of-band communication of authorization information or
use of encrypted data in special fields are the available non-standard
techniques.
9. Collected ABNF Syntax
In this section we provide a summary of ABNF specifications.
phone-string = 1*( DTMF / pause / tonewait / written-sep )
DTMF = ( DIGIT / "#" / "*" / "A" / "B" / "C" / "D" )
written-sep = ( "-" / "." )
pause = "p"
tonewait = "w"
gstn-phone = ( global-phone / local-phone )
global-phone = "+" 1*( DIGIT / written-sep )
local-phone = [ exit-code ] dial-number
local-phone =/ exit-code [ dial-number ]
exit-code = phone-string
dial-number = phone-string
subaddr-string = phone-string
post-dial = phone-string
10. 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
11. References
[1] 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)
[2] ITU E.164 - The International Public Telecommunication Numbering
Plan E.164/I.331 (May 1997)
[3] Allocchio, C., "Minimal GSTN address format in Internet Mail",
RFC 3191, October 2001
[4] Allocchio, C., "Minimal FAX address format in Internet Mail",
RFC 3192, October 2001
[5] Allocchio, C. "GSTN address element extensions in e-mail
services", RFC 2846, June 2000.
[6] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806,
April 2000.
[7] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications", RFC 2234, November 1997.
[8] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[9] ITU T.33 - Facsimile routing utilizing the subaddress;
recommendation T.33 (July, 1996)
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Received on Friday, 22 February 2002 04:38:33 UTC