Text String Notation for Dial Sequences and Global Switched Telephone Network (GSTN) / E.164 Addresses
RFC 3601

Document Type RFC - Proposed Standard (September 2003; No errata)
Was draft-allocchio-gstn (individual in app area)
Author Claudio Allocchio 
Last updated 2018-07-18
Stream IETF
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IESG IESG state RFC 3601 (Proposed Standard)
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Responsible AD Ted Hardie
IESG note published as RFC3601
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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.


   This 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.

1.  Introduction

   Since the very first devices interacting with GSTN services appeared,
   a need for a unique text string representation of commonly called
   telephone numbers, and more generally DTMF sequences and actions, was

   This memo describes the full text string representation method.  This
   specification was explicitly created to provide an easy, unique and
   complete reference which MUST be used by all other specifications
   needing a text string representation for a Dial Sequence.

   The specification was collected directly from Dial Sequence
   definitions which are already described in existing Standard Track
   specifications (such as [6] [7] [8] [9]), and is fully synchronized
   with them.  Full compatibility is thus assured, and as a consequence,
   this specification results in a compendium of existing definitions.

Allocchio                   Standards Track                     [Page 1]
RFC 3601       Dial Sequences and GSTN / E.164 Addresses  September 2003

   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 [2], 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

1.1.  Terminology and Syntax conventions

   In this document the formal definitions are described using ABNF
   syntax, as defined in [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",
   document are to be interpreted as described in BCP 14, RFC 2119 [4].

   The following terms are also defined in this document:

      Dial Sequence:
         a series of DTMF elements and human or device "actions";

         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;

         a text representation of a GSTN address;

         a text representation of a GSTN subaddress (which includes ISDN
         subaddresses [2] and T.33 subaddresses [5]);

         a text representation of a post dialling sequence.

Allocchio                   Standards Track                     [Page 2]
RFC 3601       Dial Sequences and GSTN / E.164 Addresses  September 2003

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,
   the sequences already needed to dial a gstn-phone, 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 elements": 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 readability of a Dial

2.1.  The "phone-string" definition

   The text representation of the Dial Sequence elements is defined in
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