Number Portability in the Global Switched Telephone Network (GSTN): An Overview
RFC 3482

Network Working Group                                          M. Foster
Request for Comments: 3482                                    T. McGarry
Category: Informational                                            J. Yu
                                                           NeuStar, Inc.
                                                           February 2003

  Number Portability in the Global Switched Telephone Network (GSTN):
                              An Overview

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document provides an overview of E.164 telephone number
   portability (NP) in the Global Switched Telephone Network (GSTN).
   NP is a regulatory imperative seeking to liberalize local telephony
   service competition, by enabling end-users to retain telephone
   numbers while changing service providers.  NP changes the fundamental
   nature of a dialed E.164 number from a hierarchical physical routing
   address to a virtual address, thereby requiring the transparent
   translation of the later to the former.  In addition, there are
   various regulatory constraints that establish relevant parameters for
   NP implementation, most of which are not network technology specific.
   Consequently, the implementation of NP behavior consistent with
   applicable regulatory constraints, as well as the need for
   interoperation with the existing GSTN NP implementations, are
   relevant topics for numerous areas of IP telephony works-in-progress
   with the IETF.

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RFC 3482      Number Portability in the GSTN: An Overview  February 2003

Table of Contents

   1.  Introduction .................................................  2
   2.  Abbreviations and Acronyms ...................................  4
   3.  Types of Number Portability ..................................  6
   4.  Service Provider Number Portability Schemes ..................  7
       4.1   All Call Query (ACQ) ...................................  8
       4.2   Query on Release (QoR) .................................  9
       4.3   Call Dropback .......................................... 10
       4.4   Onward Routing (OR) .................................... 11
       4.5   Comparisons of the Four Schemes ........................ 11
   5.  Database Queries in the NP Environment ....................... 13
       5.1   U.S. and Canada ........................................ 13
       5.2   Europe ................................................. 14
   6.  Call Routing in the NP Environment ........................... 15
       6.1   U.S. and Canada ........................................ 16
       6.2   Europe ................................................. 17
   7.  NP Implementations for Geographic E.164 Numbers .............. 19
   8.  Number Conservation Method Enabled By NP ..................... 22
       8.1   Block Pooling .......................................... 22
       8.2   ITN Pooling ............................................ 23
   9.  Potential Implications ....................................... 23
   10. Security Considerations ...................................... 27
   11. IANA Considerations .......................................... 27
   12. Normative References ......................................... 27
   13. Informative References ....................................... 28
   14. Acknowledgement .............................................. 29
   15. Authors' Addresses ........................................... 29
   16. Full Copyright Statement ..................................... 30

1. Introduction

   This document provides an overview of E.164 telephone number [E164]
   portability in the Global Switched Telephone Network (GSTN).  There
   are considered to be three types of number portability (NP): service
   provider number portability (SPNP), location portability (not to be
   confused with terminal mobility), and service portability.

   SPNP, the focus of the present document, is a regulatory imperative
   in many countries seeking to liberalize telephony service
   competition, especially local service.  Historically, local telephony
   service (as compared to long distance or international service) has
   been regulated as a utility-like form of service.  While a number of
   countries had begun liberalization (e.g., privatization, de-
   regulation, or re-regulation) some years ago, the advent of NP is
   relatively recent (since ~1995).

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