Network Working Group C. Allocchio Request for Comments: 3601 GARR-Italy Category: Standards Track September 2003 Text String Notation for Dial Sequences and Global Switched Telephone Network (GSTN) / E.164 Addresses Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved.
AbstractThis memo describes the full set of notations needed to represent a text string in a Dial Sequence. A Dial Sequence is normally composed of Dual Tone Multi Frequency (DTMF) elements, plus separators and 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. 6]   ), and is fully synchronized with them. Full compatibility is thus assured, and as a consequence, this specification results in a compendium of existing definitions.
This notation is a fully compatible compendium of existing notations, and should be used in all specifications needing a text string representation of a Dial Sequence. Although the commonly called "telephone numbers" are normally used to generate a Dial Sequence when establishing a connection, the full abstract E.164 addresses , i.e., the universal addressing on the Global Switched Telephone Network (GSTN), have further elements which cannot be dialled. Thus abstract E.164 addresses cannot be fully converted into a Dial Sequence or fully represented using this notation. 3]. This memo also uses some of the "CORE DEFINITIONS" defined in "APPENDIX A - CORE" of that document. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 . The following terms are also defined in this document: Dial Sequence: a series of DTMF elements and human or device "actions"; phone-string: a text representation of a Dial Sequence; GSTN address: a commonly called "telephone number" on the GSTN, i.e., a diallable subset of an E.164 abstract address or any private numbering schema diallable address; gstn-phone: a text representation of a GSTN address; subaddr-string: a text representation of a GSTN subaddress (which includes ISDN subaddresses  and T.33 subaddresses ); post-dial: a text representation of a post dialling sequence.
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 are the "separators". The "pause" and "tonewait" elements interpretation of the phone- string depends on the specific devices and implementation using the specification. Thus their exact meaning is not mandated in this
document. The next section provides some examples drawn from common practice. Both "pause" and "tonewait" are case insensitive. Implementation of "pause" and "tonewait": - one instance of a "pause" SHOULD be interpreted as a pause of one second between the preceding and succeeding dial string elements; - a "tonewait" SHOULD 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 readability of the phone-string. The written-sep are elements which can be placed between dial elements, such as digits etc. Any occurrences 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. 2] represent a limited subset of all possible GSTN addresses, while the complete complex case needs a full encoding schema, as it also includes a local or private addressing 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 )
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 distance 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 Belgium (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
 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).  ITU E.164 - The International Public Telecommunication Numbering Plan E.164/I.331 (May 1997).  Crocker, D. Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
 ITU T.33 - Facsimile routing utilizing the subaddress; recommendation T.33 (July, 1996).  Allocchio, C., "Minimal GSTN address format in Internet Mail", RFC 3191, October 2001.  Allocchio, C., "Minimal FAX address format in Internet Mail", RFC 3192, October 2001.  Allocchio, C., "GSTN Address Element Extensions in E-mail Services", RFC 2846, June 2000.  Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April 2000.
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