Network Working C. Allocchio Group GARR-Italy INTERNET-DRAFT November 2001 Expires: May 2002 File: draft-allocchio-gstn-01.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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents 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 "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. 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  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")  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    ) 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 . 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 . 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  and T.33 subaddresses ); 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 . ; 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. Both "pause" and "tonewait" are case insensitive. 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  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  , which restrict the phone-string elements to 1*( DIGIT / written-sep ) and service specific subaddresses, like the fax service T.33 subaddress   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  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)  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.  Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications", 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) 12. Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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