The tel URI for Telephone Numbers
RFC 3966

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Network Working Group                                     H. Schulzrinne
Request for Comments: 3966                           Columbia University
Obsoletes: 2806                                            December 2004
Category: Standards Track

                   The tel URI for Telephone Numbers

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 (2004).

Abstract

   This document specifies the URI (Uniform Resource Identifier) scheme
   "tel".  The "tel" URI describes resources identified by telephone
   numbers.  This document obsoletes RFC 2806.

Table of Contents

   1.   Introduction. . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.   Terminology . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.   URI Syntax. . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.   URI Comparisons . . . . . . . . . . . . . . . . . . . . . . .  6
   5.   Phone Numbers and Their Context . . . . . . . . . . . . . . .  6
        5.1.   Phone Numbers. . . . . . . . . . . . . . . . . . . . .  6
               5.1.1. Separators in Phone Numbers . . . . . . . . . .  7
               5.1.2. Alphabetic Characters Corresponding to Digits .  7
               5.1.3. Alphabetic, *, and # Characters as Identifiers.  7
               5.1.4. Global Numbers. . . . . . . . . . . . . . . . .  7
               5.1.5. Local Numbers . . . . . . . . . . . . . . . . .  8
        5.2.   ISDN Subaddresses. . . . . . . . . . . . . . . . . . .  9
        5.3.   Phone Extensions . . . . . . . . . . . . . . . . . . . 10
        5.4.   Other Parameters . . . . . . . . . . . . . . . . . . . 10
   6.   Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   7.   Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 11
        7.1.   Why Not Just Put Telephone Numbers in SIP URIs?. . . . 11
        7.2.   Why Not Distinguish between Call Types?. . . . . . . . 11
        7.3.   Why tel. . . . . . . . . . . . . . . . . . . . . . . . 11
        7.4.   Do Not Confuse Numbers with How They Are Dialed. . . . 11

Schulzrinne                 Standards Track                     [Page 1]
RFC 3966                      The tel URI                  December 2004

   8.   Usage of Telephone URIs in HTML . . . . . . . . . . . . . . . 11
   9.   Use of "tel" URIs with SIP (Informative). . . . . . . . . . . 12
   10.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
   11.  Security Considerations . . . . . . . . . . . . . . . . . . . 14
   12.  Changes Since RFC 2806. . . . . . . . . . . . . . . . . . . . 14
   13.  References. . . . . . . . . . . . . . . . . . . . . . . . . . 15
        13.1.  Normative References . . . . . . . . . . . . . . . . . 15
        13.2.  Informative References . . . . . . . . . . . . . . . . 16
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 17

1.  Introduction

   This document defines the URI scheme "tel", which describes resources
   identified by telephone numbers.  A telephone number is a string of
   decimal digits that uniquely indicates the network termination point.
   The number contains the information necessary to route the call to
   this point.  (This definition is derived from [E.164] but encompasses
   both public and private numbers.)

   The termination point of the "tel" URI telephone number is not
   restricted.  It can be in the public telephone network, a private
   telephone network, or the Internet.  It can be fixed or wireless and
   address a fixed wired, mobile, or nomadic terminal.  The terminal
   addressed can support any electronic communication service (ECS),
   including voice, data, and fax.  The URI can refer to resources
   identified by a telephone number, including but not limited to
   originators or targets of a telephone call.

   The "tel" URI is a globally unique identifier ("name") only; it does
   not describe the steps necessary to reach a particular number and
   does not imply dialling semantics.  Furthermore, it does not refer to
   a specific physical device, only to a telephone number.

   As commonly understood, telephone numbers comprise two related but
   distinct concepts: a canonical address-of-record and a dial string.
   We define the concepts below:

   Address-of-record or identifier: The telephone number is understood
      here as the canonical address-of-record or identifier for a
      termination point within a specific network.  For the public
      network, these numbers follow the rules in E.164 [E.164], while
      private numbers follow the rules of the owner of the private