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77 KiB
Plaintext
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Mark Foster
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Internet Draft Tom McGarry
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Document: <draft-ietf-enum-e164-gstn-np-05.txt> James Yu
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NeuStar, Inc.
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Category: Informational June 24, 2002
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Number Portability in the GSTN: An Overview
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Status of this Memo
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This document is an Internet-Draft and is in full conformance with
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all provisions of Section 10 of RFC2026 [RFC].
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Internet-Drafts are working documents of the Internet Engineering
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Task Force (IETF), its areas, and its working groups. Note that
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other groups may also distribute working documents as Internet-
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Drafts. Internet-Drafts are draft documents valid for a maximum of
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six months and may be updated, replaced, or obsoleted by other
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documents at any time. It is inappropriate to use Internet- Drafts
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as reference material or to cite them other than as "work in
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progress."
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The list of current Internet-Drafts can be accessed at
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http://www.ietf.org/ietf/1id-abstracts.txt.
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The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html.
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Copyright Notice
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Copyright (C) The Internet Society (2002). All rights reserved.
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Abstract
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This document provides an overview of E.164 telephone number
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portability (NP) in the Global Switched Telephone Network (GSTN).
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NP is a regulatory imperative seeking to liberalize local telephony
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service competition, by enabling end-users to retain telephone
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numbers while changing service providers. NP changes the
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fundamental nature of a dialed E.164 number from a hierarchical
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physical routing address to a virtual address, thereby requiring the
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transparent translation of the later to the former. In addition,
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there are various regulatory constraints that establish relevant
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parameters for NP implementation, most of which are not network
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technology specific. Consequently, the implementation of NP
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behavior consistent with applicable regulatory constraints, as well
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as the need for interoperation with the existing GSTN NP
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implementations, are relevant topics for numerous areas of IP
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telephony work-in-progress at IETF.
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 1]
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Number Portability in the GSTN: An Overview June 24, 2002
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Table of Contents
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1. Introduction ............................................... 2
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2. Abbreviations and Acronyms ................................. 4
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3. Types of Number Portability ................................ 5
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4. Service Provider Number Portability Schemes ................ 7
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4.1 All Call Query (ACQ) .................................. 7
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4.2 Query on Release (QoR) ................................ 8
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4.3 Call Dropback ......................................... 9
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4.4 Onward Routing (OR) ................................... 9
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4.5 Comparisons of the Four Schemes ....................... 10
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5. Database Queries in the NP Environment ..................... 11
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5.1 U.S. and Canada ....................................... 12
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5.2 Europe ................................................ 13
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6. Call Routing in the NP Environment ......................... 14
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6.1 U.S. and Canada ....................................... 14
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6.2 Europe ................................................ 15
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7. NP Implementations for Geographic E.164 Numbers ............ 17
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8. Number Conservation Method Enabled By NP ................... 20
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8.1 Block Pooling ......................................... 20
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8.2 ITN Pooling ........................................... 21
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9. Potential Implications ..................................... 21
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10. Security Considerations .................................... 24
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11. IANA Considerations ........................................ 24
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12. Normative References ....................................... 24
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13. Informative References ..................................... 25
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14. Acknowledgement ............................................ 25
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15. Authors<72> Addresses ......................................... 25
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1. Introduction
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This document provides an overview of E.164 telephone number
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portability in the Global Switched Telephone Network (GSTN). There
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are considered to be three types of number portability (NP): service
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provider portability (SPNP), location portability (not to be
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confused with terminal mobility), and service portability.
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Service provider portability (SPNP), the focus of the present draft,
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is a regulatory imperative in many countries seeking to liberalize
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telephony service competition, especially local service.
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Historically, local telephony service (as compared to long distance
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or international service) has been regulated as a utility-like form
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of service. While a number of countries had begun liberalization
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(e.g. privatization, de-regulation, or re-regulation) some years
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ago, the advent of NP is relatively recent (since ~1995).
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E.164 numbers can be non-geographic and geographic numbers. Non-
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geographic numbers do not reveal the locations information of those
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numbers. Geographic E.164 numbers were intentionally designed as
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hierarchical routing addresses which could systematically be digit-
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analyzed to ascertain the country, serving network provider, serving
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 2]
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Number Portability in the GSTN: An Overview June 24, 2002
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end-office switch, and specific line of the called party. As such,
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without NP a subscriber wishing to change service providers would
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incur a number change as a consequence of being served off of a
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different end-office switch operated by the new service provider.
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The cost and convenience impact to the subscriber of changing
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numbers is seen as barrier to competition. Hence NP has become
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associated with GSTN infrastructure enhancements associated with a
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competitive environment driven by regulatory directives.
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Forms of SPNP have been deployed or are being deployed widely in the
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GSTN in various parts of the world, including the U.S., Canada,
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Western Europe, Australia, and the Pacific Rim (e.g. Hong Kong).
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Other regions, such as South America (e.g. Brazil) are actively
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considering it.
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Implementation of NP within a national telephony infrastructure
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entails potentially significant changes to numbering administration,
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network element signaling, call routing and processing, billing,
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service management, and other functions.
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NP changes the fundamental nature of a dialed E.164 number from a
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hierarchical physical routing address to a virtual address. NP
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implementations attempt to encapsulate the impacts to the GSTN and
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make NP transparent to subscribers by incorporating a translation
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function to map a dialed, potentially ported E.164 address, into a
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network routing address (either a number prefix or another E.164
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address) which can be hierarchically routed.
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This is roughly analogous to the use of network address translation
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on IP addresses to enable IP address portability by containing the
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impact of the address change to the edge of the network and retain
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the use of CIDR blocks in the core which can be route aggregated by
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the network service provider to the rest of the internet.
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NP bifurcates the historical role of a subscriber<65>s E.164 address
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into two or more data elements (a dialed or virtual address, and a
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network routing address) that must be made available to network
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elements through an NP translations database, carried by forward
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call signaling, and recorded on call detail records. Not only is
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call processing and routing affected, but also so is SS7/C7
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messaging. A number of TCAP-based SS7 messaging sets utilize an
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E.164 address as an application-level network element address in the
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global title address (GTA) field of the SCCP message header.
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Consequently, SS7/C7 signaling transfer points (STPs) and gateways
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need to be able to perform n-digit global title translation (GTT) to
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translate a dialed E.164 address into its network address
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counterpart via the NP database.
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In addition, there are various national regulatory constraints that
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establish relevant parameters for NP implementation, most of which
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are not network technology specific. Consequently, implementations
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of NP behavior in IP telephony consistent with applicable regulatory
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constraints, as well as the need for interoperation with the
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 3]
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Number Portability in the GSTN: An Overview June 24, 2002
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existing GSTN NP implementations, are relevant topics for numerous
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areas of IP telephony work-in-progress at IETF.
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This document describes three types of number portability and the
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four schemes that have been standardized to support SPNP for
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geographic E.164 numbersspecifically. Following that, specific
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information regarding the call routing and database query
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implementations are described for several regions (North American
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and Europe) and industries (wireless vs. wireline). The Number
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Portability Database (NPDB) interfaces and the call routing schemes
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that are used in the North America and Europe are described to show
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the variety of standards that may be implemented worldwide. A
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glance of the NP implementations worldwide is provided. Number
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pooling is briefly discussed to show how NP is being enhanced in the
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U.S. to conserve North American area codes. The conclusion briefly
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touches the potential impacts of NP on IP & Telecommunications
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Interoperability. Appendix A provides some specific technical and
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regulatory information on NP in North America. Appendix B describes
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the number portability administration process that manages the
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number portability database in North America.
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2. Abbreviations and Acronyms
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ACQ All Call Query
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AIN Advanced Intelligent Network
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AMPS Advanced Mobile Phone System
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ANSI American National Standards Institute
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CDMA Code Division Multiple Access
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CdPA Called Party Address
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CdPN Called Party Number
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CH Code Holder
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CMIP Common Management Information Protocol
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CS1 Capability Set 1
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CS2 Capability Set 2
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DN Directory Number
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DNS Domain Name System
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ETSI European Technical Standards Institute
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FCI Forward Call Indicator
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GAP Generic Address Parameter
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GMSC Gateway Mobile Services Switching Center or Gateway Mobile
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Switching Center
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GSM Global System for Mobile Communications
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GSTN Global Switched Telephone Network
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GW Gateways
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HLR Home Location Register
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IAM Initial Address Message
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IETF Internet Engineering Task Force
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ILNP Interim LNP
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IN Intelligent Network
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INAP Intelligent Network Application Part
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INP Interim NP
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IP Internet Protocol
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IS-41 Interim Standards Number 41
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 4]
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Number Portability in the GSTN: An Overview June 24, 2002
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ISDN Integrated Services Digital Network
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ISUP ISDN User Part
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ITN Individual Telephony Number
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ITU International Telecommunication Union
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ITU-TS ITU-Telecommunication Sector
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LDAP Lightweight Directory Access Protocol
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LEC Local Exchange Carrier
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LERG Local Exchange Routing Guide
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LNP Local Number Portability
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LRN Location Routing Number
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MAP Mobile Application Part
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MNP Mobile Number Portability
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MSRN Mobile Station Roaming Number
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MTP Message Transfer Part
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NANP North American Numbering Plan
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NP Number Portability
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NPDB Number Portability Database
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NRN Network Routing Number
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OR Onward Routing
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OSS Operation Support System
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PCS Personal Communication Services
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PNTI Ported Number Translation Indicator
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PODP Public Office Dialing Plan
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PUC Public Utility Commission
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QoR Query on Release
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RN Routing Number
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RTP Return to Pivot
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SCCP Signaling Connection Control Part
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SCP Service Control Point
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SIP Session Initiation Protocol
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SMR Special Mobile Radio
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SMS Service Management System
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SPNP Service Provider Number Portability
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SRF Signaling Relaying Function
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SRI Send Routing Information
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SS7 Signaling System Number 7
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STP Signaling Transfer Point
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TCAP Transaction Capabilities Application Part
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TDMA Time Division Multiple Access
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TN Telephone Number
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TRIP Telephony Routing Information Protocol
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URL Universal Resource Locator
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U.S. United States
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3. Types of Number Portability
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As there are several types of E.164 numbers (telephone numbers, or
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just TN) in the GSTN, there are correspondingly several types of
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E.164 NP in the GSTN. First there are so-call non-geographic E.164
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numbers, commonly used for service-specific applications such as
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freephone (800 or 0800). Portability of these numbers is called
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non-geographic number portability (NGNP). NGNP, for example, was
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deployed in the U.S. in 1986-92.
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 5]
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Number Portability in the GSTN: An Overview June 24, 2002
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Geographic number portability, which includes traditional fixed or
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wireline numbers as well as mobile numbers which are allocated out
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of geographic number range prefixes, is called NP or GNP or in the
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U.S. local number portability (LNP).
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Number portability allows the telephony subscribers in the Global
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Switched Telephone Network (GSTN) to keep their phone numbers when
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they change their service providers or subscribed services, or when
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they move to a new location.
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The ability to change the service provider while keeping the same
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phone number is called service provider portability (SPNP) also
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known as "operator portability."
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The ability to change the subscriber<65>s fixed service location while
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keeping the same phone number is called location portability.
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The ability to change the subscribed services (e.g., from the plain
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old telephone service to Integrated Services Digital Network (ISDN)
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services) while keeping the same phone number is called service
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portability. Another aspect of service portability is to allow the
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subscribers to enjoy the subscribed services in the same way when
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they roam outside their home networks as is supported by the
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cellular/wireless networks.
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In addition, mobile number portability (MNP) refers to specific NP
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implementation in mobile networks either as part of a broader NP
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implementation in the GSTN or on a stand-alone basis. Where
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interoperation of LNP and MNP is supported, service portability
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between fixed and mobile service types is possible.
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At present, SPNP has been the primary form of NP deployed due to its
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relevance in enabling local service competition.
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Also in use in the GSTN are the terms interim NP (INP) or Interim
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LNP (ILNP) and true NP. Interim NP usually refers to the use of
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remote call forwarding-like measures to forward calls to ported
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numbers through the donor network to the new service network. These
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are considered interim relative to true NP, which seeks to remove
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the donor network or old service provider from the call or signaling
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path altogether. Often the distinction between interim and true NP
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is a national regulatory matter relative to the
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technical/operational requirements imposed on NP in that country.
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Implementations of true NP in certain countries (e.g. U.S., Canada,
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Spain, Belgium, Denmark) may pose specific requirements for IP
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telephony implementations as a result of regulatory and industry
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requirements for providing call routing and signaling independent of
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the donor network or last previous serving network.
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Foster,McGarry,Yu Expired on December 23, 2002 [Page 6]
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Number Portability in the GSTN: An Overview June 24, 2002
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4. Service Provider Number Portability Schemes
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Four schemes can be used to support service provider portability and
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are briefly described below. But first, some further terms are
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introduced.
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The donor network is the network that first assigned a telephone
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number (e.g., TN +1-202-533-1234) to a subscriber, out of a number
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range administratively (e.g., +1 202-533) assigned to it. The
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current service provider (new SP) or new serving network is the
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network that currently serves the ported number. The old serving
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network (or old SP) is the network that previously served the ported
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number before the number was ported to the new serving network.
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Since a TN can port a number of times, the old SP is not necessarily
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the same as the donor network, except for the first time the TN
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ports away, or if the TN ports back into the donor network and away
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again. While the new SP and old SP roles are transitory as a TN
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ports around, the donor network is always the same for any
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particular TN based on the service provider to whom the subtending
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number range was administratively assigned. See the discussion
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below on number pooling, as this enhancement to NP further
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bifurcates the role of donor network into two (the number range or
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code holder network, and the block holder network).
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To simplify the illustration, all the transit networks are ignored,
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the originating or donor network is the one that performs the
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database queries or call redirection, and the dialed directory
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number (TN) has been ported out of the donor network before.
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It is assumed that the old serving network, the new serving network
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and the donor network are different networks so as to show which
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networks are involved in call handling and routing and database
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queries in each of four schemes. Please note that the port of the
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number (process of moving it from one network to another) happened
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prior to the call setup and is not included in the call steps.
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Information carried in the signaling messages to support each of the
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four schemes is not discussed to simplify the explanation.
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|
4.1 All Call Query (ACQ)
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Figure 1 shows the call steps for the ACQ scheme. Those call steps
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|||
|
are as follows:
|
|||
|
|
|||
|
(1) The Originating Network receives a call from the caller and
|
|||
|
sends a query to a centrally administered Number Portability
|
|||
|
Database (NPDB), a copy of which is usually resident on a
|
|||
|
network element within its network or through a third party
|
|||
|
provider.
|
|||
|
(2) The NPDB returns the routing number associated with the dialed
|
|||
|
directory number. The routing number is discussed later in
|
|||
|
Section 6.
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 7]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
(3) The Originating Network uses the routing number to route the
|
|||
|
call to the new serving network.
|
|||
|
|
|||
|
|
|||
|
+-------------+ +-----------+ Number +-----------+
|
|||
|
| Centralized | | New Serv. | ported | Old Serv. |
|
|||
|
| NPDB | +-------->| Network |<------------| Network |
|
|||
|
+-------------+ | +-----------+ +-----------+
|
|||
|
^ | |
|
|||
|
| | |
|
|||
|
1| | 3.|
|
|||
|
| | 2. |
|
|||
|
| | |
|
|||
|
| v |
|
|||
|
+----------+ | +----------+ +----------+
|
|||
|
| Orig. |------+ | Donor | | Internal |
|
|||
|
| Network | | Network | | NPDB |
|
|||
|
+----------+ +----------+ +----------+
|
|||
|
|
|||
|
|
|||
|
Figure 1 - All Call Query (ACQ) Scheme.
|
|||
|
|
|||
|
|
|||
|
4.2 Query on Release (QoR)
|
|||
|
|
|||
|
Figure 2 shows the call steps for the QoR scheme. Those call steps
|
|||
|
are as follows:
|
|||
|
|
|||
|
|
|||
|
+-------------+ +-----------+ Number +-----------+
|
|||
|
| Centralized | | New Serv. | ported | Old Serv. |
|
|||
|
| NPDB | | Network |<------------| Network |
|
|||
|
+-------------+ +-----------+ +-----------+
|
|||
|
^ | ^
|
|||
|
| | 4. |
|
|||
|
3.| | 5. |
|
|||
|
| | +----------------------+
|
|||
|
| | |
|
|||
|
| v |
|
|||
|
+----------+ 2. +----------+ +----------+
|
|||
|
| Orig. |<---------------| Donor | | Internal |
|
|||
|
| Network |--------------->| Network | | NPDB |
|
|||
|
+----------+ 1. +----------+ +----------+
|
|||
|
|
|||
|
|
|||
|
Figure 2 - Query on Release (QoR) Scheme.
|
|||
|
|
|||
|
(1) The Originating Network receives a call from the caller and
|
|||
|
routes the call to the donor network.
|
|||
|
(2) The donor network releases the call and indicates that the
|
|||
|
dialed directory number has been ported out of that switch.
|
|||
|
(3) The Originating Network sends a query to its copy of the
|
|||
|
centrally administered NPDB.
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 8]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
(4) The NPDB returns the routing number associated with the dialed
|
|||
|
directory number.
|
|||
|
(5) The Originating Network uses the routing number to route the
|
|||
|
call to the new serving network.
|
|||
|
|
|||
|
|
|||
|
4.3 Call Dropback
|
|||
|
|
|||
|
Figure 3 shows the call steps for the Dropback scheme. This scheme
|
|||
|
is also known as "Return to Pivot (RTP)." Those call steps are as
|
|||
|
follows:
|
|||
|
|
|||
|
(1) The Originating Network receives a call from the caller and
|
|||
|
routes the call to the donor network.
|
|||
|
(2) The donor network detects that the dialed directory number has
|
|||
|
been ported out of the donor switch and checks with an internal
|
|||
|
network-specific NPDB.
|
|||
|
(3) The internal NPDB returns the routing number associated with the
|
|||
|
dialed directory number.
|
|||
|
(4) The donor network releases the call by providing the routing
|
|||
|
number.
|
|||
|
(5) The Originating Network uses the routing number to route the
|
|||
|
call to the new serving network.
|
|||
|
|
|||
|
+-------------+ +-----------+ Number +-----------+
|
|||
|
| Centralized | | New Serv. | porting | Old Serv. |
|
|||
|
| NPDB | | Network |<------------| Network |
|
|||
|
+-------------+ +-----------+ +-----------+
|
|||
|
/\
|
|||
|
|
|
|||
|
5. |
|
|||
|
+------------------------+
|
|||
|
|
|
|||
|
|
|
|||
|
+----------+ 4. +----------+ 3. +----------+
|
|||
|
| Orig. |<---------------| Donor |<----------| Internal |
|
|||
|
| Network |--------------->| Network |---------->| NPDB |
|
|||
|
+----------+ 1. +----------+ 2. +----------+
|
|||
|
|
|||
|
|
|||
|
Figure 3 - Dropback Scheme.
|
|||
|
|
|||
|
|
|||
|
4.4 Onward Routing (OR)
|
|||
|
|
|||
|
Figure 4 shows the call steps for the OR scheme. Those call steps
|
|||
|
are as follows:
|
|||
|
|
|||
|
(1) The Originating Network receives a call from the caller and
|
|||
|
routes the call to the donor network.
|
|||
|
(2) The donor network detects that the dialed directory number has
|
|||
|
been ported out of the donor switch and checks with an internal
|
|||
|
network-specific NPDB.
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 9]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
(3) The internal NPDB returns the routing number associated with the
|
|||
|
dialed directory number.
|
|||
|
(4) The donor network uses the routing number to route the call to
|
|||
|
the new serving network.
|
|||
|
|
|||
|
|
|||
|
+-------------+ +-----------+ Number +-----------+
|
|||
|
| Centralized | | New Serv. | porting | Old Serv. |
|
|||
|
| NPDB | | Network |<------------| Network |
|
|||
|
+-------------+ +-----------+ +-----------+
|
|||
|
/\
|
|||
|
|
|
|||
|
4.|
|
|||
|
|
|
|||
|
+----------+ +----------+ 3. +----------+
|
|||
|
| Orig. | | Donor |<----------| Internal |
|
|||
|
| Network |--------------->| Network |---------->| NPDB |
|
|||
|
+----------+ 1. +----------+ 2. +----------+
|
|||
|
|
|||
|
|
|||
|
Figure 4 - Onward Routing (OR) Scheme.
|
|||
|
|
|||
|
4.5 Comparisons of the Four Schemes
|
|||
|
|
|||
|
Only the ACQ scheme does not involve the donor network when routing
|
|||
|
the call to the new serving network of the dialed ported number.
|
|||
|
The other three schemes involve call setup to or signaling with the
|
|||
|
donor network.
|
|||
|
|
|||
|
Only the OR scheme requires the setup of two physical call segments,
|
|||
|
one from the Originating Network to the donor network and the other
|
|||
|
from the donor network to the new serving network. The OR scheme is
|
|||
|
the least efficient in terms of using the network transmission
|
|||
|
facilities. The QoR and Dropback schemes set up calls to the donor
|
|||
|
network first but release the call back to the Originating Network
|
|||
|
that then initiates a new call to the Current Serving Network. For
|
|||
|
the QoR and Dropback schemes, circuits are still reserved one by one
|
|||
|
between the Originating Network and the donor network when the
|
|||
|
Originating Network sets up the call towards the donor network.
|
|||
|
Those circuits are released one by one when the call is released
|
|||
|
from the donor network back to the Originating Network. The ACQ
|
|||
|
scheme is the most efficient in terms of using the switching and
|
|||
|
transmission facilities for the call.
|
|||
|
|
|||
|
Both the ACQ and QoR schemes involve Centralized NPDBs for the
|
|||
|
Originating Network to retrieve the routing information.
|
|||
|
Centralized NPDB means that the NPDB contains ported number
|
|||
|
information from multiple networks. This is in contrast to the
|
|||
|
internal network-specific NPDB that is used for the Dropback and OR
|
|||
|
schemes. The internal NPDB only contains information about the
|
|||
|
numbers that were ported out of the donor network. The internal
|
|||
|
NPDB can be a stand-alone database that contains information about
|
|||
|
all or some ported-out numbers from the donor network. It can also
|
|||
|
reside on the donor switch and only contains information about those
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 10]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
numbers ported out of the donor switch. In that case, no query to a
|
|||
|
stand-alone internal NPDB is required. The donor switch for a
|
|||
|
particular phone number is the switch to which the number range is
|
|||
|
assigned from which that phone number was originally assigned.
|
|||
|
|
|||
|
For example, number ranges in the North American Numbering Plan
|
|||
|
(NANP) are usually assigned in the form of central office codes (CO
|
|||
|
codes) comprising a six-digit prefix formatted as a NPA+NXX. Thus a
|
|||
|
switch serving +1-202-533 would typically serve +1-202-533-0000
|
|||
|
through +1-202-533-9999. In major cities, switches usually host
|
|||
|
several CO codes. NPA stands for Numbering Plan Area that is also
|
|||
|
known as the area code. It is three-digit long and has the format
|
|||
|
of NXX where N is any digit from 2 to 9 and X is any digit from 0 to
|
|||
|
9. NXX in the NPA+NXX format is known as the office code that has
|
|||
|
the same format as the NPA. When a NPA+NXX code is set as
|
|||
|
<20>portable<6C> in the Local Exchange Routing Guide (LERG), it becomes a
|
|||
|
"portable NPA+NXX" code.
|
|||
|
|
|||
|
Similarly, in other national E.164 numbering plans, number ranges
|
|||
|
cover a contiguous range of numbers within that range. Once a
|
|||
|
number within that range has ported away from the donor network, all
|
|||
|
numbers in that range are considered potentially ported and should
|
|||
|
be queried in the NPDB.
|
|||
|
|
|||
|
The ACQ scheme has two versions. One version is for the Originating
|
|||
|
Network to always query the NPDB when a call is received from the
|
|||
|
caller regardless whether the dialed directory number belongs to any
|
|||
|
number range that is portable or has at least one number ported out.
|
|||
|
The other version is to check whether the dialed directory number
|
|||
|
belongs to any number range that is portable or has at least one
|
|||
|
number ported out. If yes, an NPDB query is sent. If not, no NPDB
|
|||
|
query is sent. The former performs better when there are many
|
|||
|
portable number ranges. The latter performs better when there are
|
|||
|
not too many portable number ranges at the expense of checking every
|
|||
|
call to see whether NPDB query is needed. The latter ACQ scheme is
|
|||
|
similar to the QoR scheme except that the QoR scheme uses call setup
|
|||
|
and relies on the donor network to indicate "number ported out"
|
|||
|
before launching the NPDB query.
|
|||
|
|
|||
|
|
|||
|
5. Database Queries in the NP Environment
|
|||
|
|
|||
|
As indicated earlier, the ACQ and QoR schemes require that a switch
|
|||
|
query the NPDB for routing information. Various standards have been
|
|||
|
defined for the switch-to-NPDB interface. Those interfaces with
|
|||
|
their protocol stacks are briefly described below. The term "NPDB"
|
|||
|
is used for a stand-alone database that may support just one or some
|
|||
|
or all of the interfaces mentioned below. The NPDB query contains
|
|||
|
the dialed directory number and the NPDB response contains the
|
|||
|
routing number. There are certainly other information that is sent
|
|||
|
in the query and response. The primary interest is to get the
|
|||
|
routing number from the NPDB to the switch for call routing.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 11]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
5.1 U.S. and Canada
|
|||
|
|
|||
|
One of the following five NPDB interfaces can be used to query an
|
|||
|
NPDB:
|
|||
|
|
|||
|
(a) Advanced Intelligent Network (AIN) using the American National
|
|||
|
Standards Institute (ANSI) version of the Intelligent Network
|
|||
|
Application Part (INAP) [ANSI SS] [ANSI DB]. The INAP is
|
|||
|
carried on top of the protocol stack that includes the (ANSI)
|
|||
|
Message Transfer Part (MTP) Levels 1 through 3, ANSI Signaling
|
|||
|
Connection Control Part (SCCP), and ANSI Transaction
|
|||
|
Capabilities Application Part (TCAP). This interface can be
|
|||
|
used by the wireline or wireless switches, is specific to the NP
|
|||
|
implementation in North America, and is modeled on the Public
|
|||
|
Office Dialing Plan (PODP) trigger defined in the Advanced
|
|||
|
Intelligent Network (AIN) 0.1 call model.
|
|||
|
|
|||
|
(b) Intelligent Network (IN), which is similar to the one used for
|
|||
|
querying the 800 databases. The IN protocol is carried on top
|
|||
|
of the protocol stack that includes the ANSI MTP Levels 1
|
|||
|
through 3, ANSI SCCP, and ANSI TCAP. This interface can be used
|
|||
|
by the wireline or wireless switches.
|
|||
|
|
|||
|
(c) ANSI IS-41 [IS41] [ISNP], which is carried on top of the
|
|||
|
protocol stack that includes the ANSI MTP Levels 1 through 3,
|
|||
|
ANSI SCCP, and ANSI TCAP. This interface can be used by the IS-
|
|||
|
41 based cellular/Personal Communication Services (PCS) wireless
|
|||
|
switches (e.g., AMPS, TDMA and CDMA). Cellular systems use
|
|||
|
spectrum at 800 MHz range and PCS systems use spectrum at 1900
|
|||
|
MHz range.
|
|||
|
|
|||
|
(d) Global System for Mobile Communication Mobile Application Part
|
|||
|
(GSM MAP) [GSM], which is carried on top of the protocol stack
|
|||
|
that includes the ANSI MTP Levels 1 through 3, ANSI SCCP, and
|
|||
|
International Telecommunication Union - Telecommunication Sector
|
|||
|
(ITU-TS) TCAP. It can be used by the PCS1900 wireless switches
|
|||
|
that are based on the GSM technologies. GSM is a series of
|
|||
|
wireless standards defined by the European Telecommunications
|
|||
|
Standards Institute (ETSI).
|
|||
|
|
|||
|
(e) ISUP triggerless translation. NP translations are performed
|
|||
|
transparently to the switching network by the signaling network
|
|||
|
(e.g. Signaling Transfer Points (STPs) or signaling gateways).
|
|||
|
ISUP IAM messages are examined to determine if the CdPN field
|
|||
|
has already been translated, and if not, an NPDB query is
|
|||
|
performed, and the appropriate parameters in the IAM message
|
|||
|
modified to reflect the results of the translation. The
|
|||
|
modified IAM message is forwarded by the signaling node on to
|
|||
|
the designated DPC in a transparent manner to continue call
|
|||
|
setup. The NPDB can be integrated with the signaling node or be
|
|||
|
accessed via an API locally or by a query to a remote NPDB using
|
|||
|
a proprietary protocol or the schemes described above.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 12]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
Wireline switches have the choice of using either (a), (b), or (e).
|
|||
|
IS-41 based wireless switches have the choice of using (a), (b),
|
|||
|
(c), or (e). PCS1900 wireless switches have the choice of using
|
|||
|
(a), (b), (d), or (e). In the United States, service provider
|
|||
|
portability will be supported by both the wireline and wireless
|
|||
|
systems, not only within the wireline or wireless domain but also
|
|||
|
across the wireline/wireless boundary. However, this is not true in
|
|||
|
Europe where service provider portability is usually supported only
|
|||
|
within the wireline or wireless domain, not across the
|
|||
|
wireline/wireless boundary due to explicit use of service-specific
|
|||
|
number range prefixes. The reason is to avoid caller confusion
|
|||
|
about the call charge. GSM systems in Europe are assigned
|
|||
|
distinctive destination network codes, and the caller pays a higher
|
|||
|
charge when calling a GSM directory number.
|
|||
|
|
|||
|
|
|||
|
5.2 Europe
|
|||
|
|
|||
|
One of the following two interfaces can be used to query an NPDB:
|
|||
|
|
|||
|
(a) Capability Set 1 (CS1) of the ITU-TS INAP [CS1], which is
|
|||
|
carried on top of the protocol stack that includes the ITU-TS
|
|||
|
MTP Levels 1 through 3, ITU-TS SCCP, and ITU-TS TCAP.
|
|||
|
|
|||
|
(b) Capability Set 2 (CS2) of the ITU-TS INAP [CS2], which is
|
|||
|
carried on top of the protocol stack that includes the ITU-TS
|
|||
|
MTP Levels 1 through ITU-TS MTP Levels 1 through 3, ITU-TS SCCP,
|
|||
|
and ITU-TS TCAP.
|
|||
|
|
|||
|
Wireline switches have the choice of using either (a) or (b);
|
|||
|
however, all the implementations in Europe so far are based on CS1.
|
|||
|
As indicated earlier that number portability in Europe does not go
|
|||
|
across the wireline/wireless boundary. The wireless switches can
|
|||
|
also use (a) or (b) to query the NPDBs if those NPDBs contains
|
|||
|
ported wireless directory numbers. The term "Mobile Number
|
|||
|
Portability (MNP)" is used for the support of service provider
|
|||
|
portability by the GSM networks in Europe.
|
|||
|
|
|||
|
In most, if not all, cases in Europe, the calls to the wireless
|
|||
|
directory numbers are routed to the wireless donor network first.
|
|||
|
Over there, an internal NPDB is queried to determine whether the
|
|||
|
dialed wireless directory number has been ported out or not. In
|
|||
|
this case, the interface to the internal NPDB is not subject to
|
|||
|
standardization.
|
|||
|
|
|||
|
MNP in Europe can also be supported via MNP Signaling Relay Function
|
|||
|
(MNP-SRF). Again, an internal NPDB or a database integrated at the
|
|||
|
MNP-SRF is used to modify the SCCP Called Party Address parameter in
|
|||
|
the GSM MAP messages so that they can be re-directed to the wireless
|
|||
|
serving network. Call routing involving MNP will be explained in
|
|||
|
Section 6.2.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 13]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
6. Call Routing in the NP Environment
|
|||
|
|
|||
|
This section discusses the call routing after the routing
|
|||
|
information has been retrieved either through an NPDB query or an
|
|||
|
internal database lookup at the donor switch, or from the Integrated
|
|||
|
Services Digital Network User Part (ISUP) signaling message (e.g.,
|
|||
|
for the Dropback scheme). For the ACQ, QoR and Dropback schemes, it
|
|||
|
is the Originating Network that has the routing information and is
|
|||
|
ready to route the call. For the OR scheme, it is the donor network
|
|||
|
that has the routing information and is ready to route the call.
|
|||
|
|
|||
|
A number of triggering schemes may be employed that determine where
|
|||
|
in the call path the NPDB query is performed. In the U.S. an <20>N-1<>
|
|||
|
policy is used, which essentially says that for domestic calls, the
|
|||
|
originating local carriers performs the query, otherwise, the long
|
|||
|
distance carrier is expected to. To ensure independence of the
|
|||
|
actual trigger policy employed in any one carrier, forward call
|
|||
|
signaling is used to flag that an NPDB query has already been
|
|||
|
performed and to therefore suppress any subsequent NP triggers that
|
|||
|
may be encountered in downstream switches, in downstream networks.
|
|||
|
This allows the earliest able network in the call path to perform
|
|||
|
the query without introducing additional costs and call setup delays
|
|||
|
were redundant queries performed downstream.
|
|||
|
|
|||
|
|
|||
|
6.1 U.S. and Canada
|
|||
|
|
|||
|
In the U.S. and Canada, a ten-digit North American Numbering Plan
|
|||
|
(NANP) number called Location Routing Number (LRN) is assigned to
|
|||
|
every switch involved in NP. In the NANP, a switch is not reachable
|
|||
|
unless it has a unique number range (CO code) assigned to it.
|
|||
|
Consequently, the LRN for a switch is always assigned out of a CO
|
|||
|
code that is assigned to that switch.
|
|||
|
|
|||
|
The LRN assigned to a switch currently serving a particular ported
|
|||
|
telephone number is returned as the network routing address in the
|
|||
|
NPDB response. The service portability scheme that was adopted in
|
|||
|
the North America is very often referred to as the LRN scheme or
|
|||
|
method.
|
|||
|
|
|||
|
LRN serves as a network address for terminating calls served off
|
|||
|
that switch using ported numbers. The LRN is assigned by the switch
|
|||
|
operator using any of the unique CO codes (NPA+NXX) assigned to that
|
|||
|
switch. The LRN is considered a non-dialable address, as the same
|
|||
|
10-digit number value may be assigned to a line on that switch. A
|
|||
|
switch may have more than one LRN.
|
|||
|
|
|||
|
During call routing/processing, a switch performs an NPDB query to
|
|||
|
obtain the LRN associated with the dialed directory number. NPDB
|
|||
|
queries are performed for all the dialed directory numbers whose
|
|||
|
NPA+NXX codes are marked as portable NPA+NXX at that switch. When
|
|||
|
formulating the ISUP Initial Address Message (IAM) to be sent to the
|
|||
|
next switch, the switch puts the ten-digit LRN in the ISUP Called
|
|||
|
Party Number (CdPN) parameter and the originally dialed directory
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 14]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
number in the ISUP Generic Address parameter (GAP). A new code in
|
|||
|
the GAP was defined to indicate that the address information in the
|
|||
|
GAP is the dialed directory number. A new bit in the ISUP Forward
|
|||
|
Call Indicator (FCI) parameter, the Ported Number Translation
|
|||
|
Indicator (PNTI) bit, is set to imply that NPDB query has already
|
|||
|
been performed. All the switches in the downstream will not perform
|
|||
|
the NPDB query if the PNTI bit is set.
|
|||
|
|
|||
|
When the terminating switch receives the IAM and sees the PNTI bit
|
|||
|
in the FCI parameter set and its own LRN in the CdPN parameter, it
|
|||
|
retrieves the originally dialed directory number from the GAP and
|
|||
|
uses the dialed directory number to terminate the call.
|
|||
|
|
|||
|
A dialed directory number with a portable NPA+NXX does not imply
|
|||
|
that directory number has been ported. The NPDBs currently do not
|
|||
|
store records for non-ported directory numbers. In that case, the
|
|||
|
NPDB will return the same dialed directory number instead of the
|
|||
|
LRN. The switch will then set the PNTI bit but keep the dialed
|
|||
|
directory number in the CdPN parameter.
|
|||
|
|
|||
|
In the real world environment, the Originating Network is not always
|
|||
|
the one that performs the NPDB query. For example, it is usually
|
|||
|
the long distance carriers that query the NPDBs for long distance
|
|||
|
calls. In that case, the Originating Network operated by the local
|
|||
|
exchange carrier (LEC) simply routes the call to the long distance
|
|||
|
carrier that is to handle that call. A wireless network acting as
|
|||
|
the Originating Network can also route the call to the
|
|||
|
interconnected local exchange carrier network if it does not want to
|
|||
|
support the NPDB interface at its mobile switches.
|
|||
|
|
|||
|
|
|||
|
6.2 Europe
|
|||
|
|
|||
|
In some European countries, a routing number is prefixed to the
|
|||
|
dialed directory number. The ISUP CdPN parameter in the IAM will
|
|||
|
contain the routing prefix and the dialed directory number. For
|
|||
|
example, United Kingdom uses routing prefixes with the format of
|
|||
|
5XXXXX and Italy uses C600XXXXX as the routing prefix. The networks
|
|||
|
use the information in the ISUP CdPN parameter to route the call to
|
|||
|
the New/Current Serving Network.
|
|||
|
|
|||
|
The routing prefix can identify the Current Serving Network or the
|
|||
|
Current Serving Switch of a ported number. For the former case,
|
|||
|
another query to the "internal" NPDB at the Current Serving Network
|
|||
|
is required to identify the Current Serving Switch before routing
|
|||
|
the call to that switch. This shields the Current Serving Switch
|
|||
|
information for a ported number from the other networks at the
|
|||
|
expense of an additional NPDB query. Another routing number, may be
|
|||
|
meaningful within the Current Serving Network, will replace the
|
|||
|
previously prefixed routing number in the ISUP CdPN parameter. For
|
|||
|
the latter case, the call is routed to the Current Serving Switch
|
|||
|
without an additional NPDB query.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 15]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
When the terminating switch receives the IAM and sees its own
|
|||
|
routing prefix in the CdPN parameter, it retrieves the originally
|
|||
|
dialed directory number after the routing prefix, and uses the
|
|||
|
dialed directory number to terminate the call.
|
|||
|
|
|||
|
The call routing example described above shows one of the three
|
|||
|
methods that can be used to transport the Directory Number (DN) and
|
|||
|
the Routing Number (RN) in the ISUP IAM message. In addition, some
|
|||
|
other information may be added/modified as is listed in the ETSI 302
|
|||
|
097 document [ETSIISUP], which is based on the ITU-T Recommendation
|
|||
|
Q.769.1 [ITUISUP]. The three methods and the enhancements in the
|
|||
|
ISUP to support number portability are briefly described below
|
|||
|
|
|||
|
(a) Two separate parameters with the CdPN parameter containing the
|
|||
|
RN and a new Called Directory Number (CdDN) parameter containing
|
|||
|
the DN. A new value for the Nature of Address (NOA) indicator in
|
|||
|
the CdPN parameter is defined to indicate that the RN is in the
|
|||
|
CdPN parameter. The switches use the CdPN parameter to route the
|
|||
|
call as is done today.
|
|||
|
|
|||
|
(b) Two separate parameters with the CdPN parameter containing the
|
|||
|
DN and a new Network Routing Number (NRN) parameter containing
|
|||
|
the RN. This method requires that the switches use the NRN
|
|||
|
parameter to route the call.
|
|||
|
|
|||
|
(c) Concatenated parameter with the CdPN parameter containing the RN
|
|||
|
plus the DN. A new Nature of Address (NOA) indicator in the CdPN
|
|||
|
parameter is defined to indicate that the RN is concatenated with
|
|||
|
the DN in the CdPN parameter. Some countries may not use new NOA
|
|||
|
value because the routing prefix does not overlap with the dialed
|
|||
|
directory numbers. But if the routing prefix overlaps with the
|
|||
|
dialed directory numbers, a new NOA value must be assigned. For
|
|||
|
example, Spain uses "XXXXXX" as the routing prefix to identify
|
|||
|
the new serving network and uses a new NOA value of 126.
|
|||
|
|
|||
|
There is also a network option to add a new ISUP parameter called
|
|||
|
Number Portability Forwarding Information parameter. This parameter
|
|||
|
has a four-bit Number Portability Status Indicator field that can
|
|||
|
provide an indication whether number portability query is done for
|
|||
|
the called directory number and whether the called directory number
|
|||
|
is ported or not if the number portability query is done.
|
|||
|
|
|||
|
Please note that all those NP enhancements for a ported number can
|
|||
|
only be used in the country that defined them. This is because
|
|||
|
number portability is supported within a nation. Within each
|
|||
|
nation, the telecommunications industry or the regulatory bodies can
|
|||
|
decide which method or methods to use. Number portability related
|
|||
|
parameters and coding are usually not passed across the national
|
|||
|
boundaries unless the interconnection agreements allow that. For
|
|||
|
example, a UK routing prefix can only be used in UK, and would cause
|
|||
|
routing problem if it appears outside UK.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 16]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
As indicated earlier, an originating wireless network can query the
|
|||
|
NPDB and concatenate the RN with DN in the CdPN parameter and route
|
|||
|
the call directly to the Current Serving Network.
|
|||
|
|
|||
|
If NPDBs do not contain information about the wireless directory
|
|||
|
numbers, the call, originated from either a wireline or a wireless
|
|||
|
network, will be routed to the Wireless donor network. Over there,
|
|||
|
an internal NPDB is queried to retrieve the RN that then is
|
|||
|
concatenated with the DN in the CdPN parameter.
|
|||
|
|
|||
|
There are several ways of realizing MNP. When MNP-SRF is supported,
|
|||
|
the Gateway Mobile Services Switching Center (GMSC) at the wireless
|
|||
|
donor network, when receiving a call from the wireline network, can
|
|||
|
send the GSM MAP Send Routing Information (SRI) message to the MNP-
|
|||
|
SRF. The MNP-SRF interrogates an internal or integrated NPDB for
|
|||
|
the RN of the MNP-SRF of the wireless Current Serving Network and
|
|||
|
prefixes the RN to the dialed wireless directory number in the
|
|||
|
global title address information in the SCCP Called Party Address
|
|||
|
(CdPA) parameter. This SRI message will be routed to the MNP-SRF of
|
|||
|
the wireless Current Serving Network, which then responds with an
|
|||
|
acknowledgement by providing the RN plus the dialed wireless
|
|||
|
directory number as the Mobile Station Roaming Number (MSRN). The
|
|||
|
GMSC of the wireless donor network formulates the ISUP IAM with the
|
|||
|
RN plus the dialed wireless directory number in the CdPN parameter
|
|||
|
and routes the call to the wireless Current Serving Network. A GMSC
|
|||
|
of the wireless Current Serving Network receives the call and sends
|
|||
|
an SRI message to the associated MNP-SRF where the global title
|
|||
|
address information of the SCCP CdPA parameter contains only the
|
|||
|
dialed wireless directory number. The MNP-SRF then replaces the
|
|||
|
global title address information in the SCCP CdPA parameter with the
|
|||
|
address information associated with a Home Location Register (HLR)
|
|||
|
that hosts the dialed wireless directory number and forwards the
|
|||
|
message to that HLR after verifying that the dialed wireless
|
|||
|
directory number is a ported-in number. The HLR then returns an
|
|||
|
acknowledgement by providing an MSRN for the GMSC to route the call
|
|||
|
to the MSC that currently serves the mobile station that is
|
|||
|
associated with the dialed wireless directory number. Please see
|
|||
|
[MNP] for details and additional scenarios.
|
|||
|
|
|||
|
|
|||
|
7. NP Implementations for Geographic E.164 Numbers
|
|||
|
|
|||
|
This section shows the known SPNP implementations worldwide.
|
|||
|
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Country + SPNP Implementation +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Argentina + Analyzing operative viability now. Will determine +
|
|||
|
+ + whether portability should be made obligatory +
|
|||
|
+ + after a technical solution has been determined. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Australia + NP supported by wireline operators since 11/30/99. +
|
|||
|
+ + NP among wireless operators in March/April 2000, +
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 17]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
+ + but may be delayed to 1Q01. The access provider +
|
|||
|
+ + or long distance provider has the obligation to +
|
|||
|
+ + route the call to the correct destination. The +
|
|||
|
+ + donor network is obligated to maintain and make +
|
|||
|
+ + available a register of numbers ported away from +
|
|||
|
+ + its network. Telstra uses onward routing via an +
|
|||
|
+ + on-switch solution. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Austria + Uses onward routing at the donor network. Routing +
|
|||
|
+ + prefix is "86xx" where "xx" identifies the +
|
|||
|
+ + recipient network. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Belgium + ACQ selected by the industry. Routing prefix is +
|
|||
|
+ + "Cxxxx" where "xxxx" identifies the recipient +
|
|||
|
+ + switch. Another routing prefix is "C00xx" with "xx"+
|
|||
|
+ + identifying the recipient network. Plan to use NOA+
|
|||
|
+ + to identify concatenated numbers and abandon the +
|
|||
|
+ + hexadecimal routing prefix. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Brazil + Considering NP for wireless users. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Chile + There has been discussions lately on NP. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Colombia + There was an Article 3.1 on NP to support NP prior +
|
|||
|
+ + to December 31, 1999 when NP became technically +
|
|||
|
+ + possible. Regulator has not yet issued regulations +
|
|||
|
+ + concerning this matter. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Denmark + Uses ACQ. Routing number not passed between +
|
|||
|
+ + operators; however, NOA is set to "112" to +
|
|||
|
+ + indicate "ported number." QoR can be used based +
|
|||
|
+ + on bilateral agreements. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Finland + Uses ACQ. Routing prefix is "1Dxxy" where "xxy" +
|
|||
|
+ + identifies the recipient network and service type. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ France + Uses onward routing. Routing prefix is "Z0xxx" +
|
|||
|
+ + where "xxx" identifies the recipient switch. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Germany + The originating network needs to do necessary +
|
|||
|
+ + rerouting. Operators decide their own solution(s).+
|
|||
|
+ + Deutsche Telekom uses ACQ. Routing prefix is +
|
|||
|
+ + "Dxxx" where "xxx" identifies the recipient +
|
|||
|
+ + network. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Hong Kong + Recipient network informs other networks about +
|
|||
|
+ + ported-in numbers. Routing prefix is "14x" where +
|
|||
|
+ + "14x" identifies the recipient network, or a +
|
|||
|
+ + routing number of "4x" plus 7 or 8 digits is used +
|
|||
|
+ + where "4x" identifies the recipient network and +
|
|||
|
+ + the rest of digits identify the called party. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Ireland + Operators choose their own solution but use onward +
|
|||
|
+ + routing now. Routing prefix is "1750" as the intra-+
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 18]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
+ + network routing code (network-specific) and +
|
|||
|
+ + "1752xxx" to "1759xxx" for GNP where "xxx" +
|
|||
|
+ + identifies the recipient switch. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Italy + Uses onward routing. Routing prefix is "C600xxxxx" +
|
|||
|
+ + where "xxxxx" identifies the recipient switch. +
|
|||
|
+ + Telecom Italia uses IN solution and other operators+
|
|||
|
+ + use on-switch solution. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Japan + Uses onward routing. Donor switch uses IN to get +
|
|||
|
+ + routing number. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Mexico + NP is considered in the Telecom law; however, the +
|
|||
|
+ + regulator (Cofetel) or the new local entrants have +
|
|||
|
+ + started no initiatives on this process. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Netherlands + Operators decide NP scheme to use. Operators have +
|
|||
|
+ + chosen ACQ or QoR. KPN implemented IN solution +
|
|||
|
+ + similar to U.S. solution. Routing prefix is not +
|
|||
|
+ + passed between operators. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Norway + OR for short-term and ACQ for long-term. QoR is +
|
|||
|
+ + optional. Routing prefix can be "xxx" with NOA=8, +
|
|||
|
+ + or "142xx" with NOA=3 where "xxx" or "xx" +
|
|||
|
+ + identifies the recipient network. +
|
|||
|
+------------ +----------------------------------------------------+
|
|||
|
+ Peru + Wireline NP may be supported in 2001. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Portugal + No NP today. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Spain + Uses ACQ. Telefonica uses QoR within its network. +
|
|||
|
+ + Routing prefix is "xxyyzz" where "xxyyzz" +
|
|||
|
+ + identifies the recipient network. NOA is set to +
|
|||
|
+ + 126. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Sweden + Standardized the ACQ but OR for operators without +
|
|||
|
+ + IN. Routing prefix is "xxx" with NOA=8 or "394xxx" +
|
|||
|
+ + with NOA=3 where "xxx" identifies the recipient +
|
|||
|
+ + network. But operators decide NP scheme to use. +
|
|||
|
+ + Telia uses onward routing between operators. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ Switzerland + Uses OR now and QoR in 2001. Routing prefix is +
|
|||
|
+ + "980xxx" where "xxx" identifies the recipient +
|
|||
|
+ + network. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ UK + Uses onward routing. Routing prefix is "5xxxxx" +
|
|||
|
+ + where "xxxxx" identifies the recipient switch. NOA +
|
|||
|
+ + is 126. BT uses the dropback scheme in some parts +
|
|||
|
+ + of its network. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
+ US + Uses ACQ. "Location Routing Number (LRN)" is used +
|
|||
|
+ + in the Called Party Number parameter. Called party+
|
|||
|
+ + number is carried in the Generic Address Parameter +
|
|||
|
+ + Use a PNTI indicator in the Forward Call Indicator +
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 19]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
+ + parameter to indicate that NPDB dip has been +
|
|||
|
+ + performed. +
|
|||
|
+-------------+----------------------------------------------------+
|
|||
|
|
|||
|
|
|||
|
8. Number Conservation Methods Enabled by NP
|
|||
|
|
|||
|
In addition to porting numbers NP provides the ability for number
|
|||
|
administrators to assign numbering resources to operators in smaller
|
|||
|
increments. Today it is common for numbering resources to be
|
|||
|
assigned to telephone operators in a large block of consecutive
|
|||
|
telephone numbers (TNs). For example, in North America each of
|
|||
|
these blocks contains 10,000 TNs and is of the format NXX+0000 to
|
|||
|
NXX+9999. Operators are assigned a specific NXX, or block. That
|
|||
|
operator is referred to as the block holder. In that block there
|
|||
|
are 10,000 TNs with line numbers ranging from 0000 to 9999.
|
|||
|
|
|||
|
Instead of assigning an entire block to the operator NP allows the
|
|||
|
administrator to assign a sub-block or even an individual telephone
|
|||
|
number. This is referred to as block pooling and individual
|
|||
|
telephone number (ITN) pooling, respectively.
|
|||
|
|
|||
|
|
|||
|
8.1 Block Pooling
|
|||
|
|
|||
|
Block Pooling refers to the process whereby the number administrator
|
|||
|
assigns a range of numbers defined by a logical sub-block of the
|
|||
|
existing block. Using North America as an example, block pooling
|
|||
|
would allow the administrator to assign sub-blocks of 1,000 TNs to
|
|||
|
multiple operators. That is, NXX+0000 to NXX+0999 can be assigned
|
|||
|
to operator A, NXX+1000 to NXX+1999 can be assigned to operator B,
|
|||
|
NXX-2000 to 2999 can be assigned to operator C, etc. In this
|
|||
|
example block pooling divides one block of 10,000 TNs into ten
|
|||
|
blocks of 1,000 TNs.
|
|||
|
|
|||
|
Porting the sub-blocks from the block holder enables block pooling.
|
|||
|
Using the example above operator A is the block holder, as well as,
|
|||
|
the holder of the first sub-block, NXX+0000 to NXX+0999. The second
|
|||
|
sub-block, NXX+1000 to NXX+1999, is ported from operator A to
|
|||
|
operator B. The third sub-block, NXX+2000 to NXX+2999, is ported
|
|||
|
from operator A to operator C, and so on. NP administrative
|
|||
|
processes and call processing will enable proper and efficient
|
|||
|
routing.
|
|||
|
|
|||
|
From a number administration and NP administration perspective block
|
|||
|
pooling introduces a new concept, that of the sub-block holder.
|
|||
|
Block pooling requires coordination between the number
|
|||
|
administrator, the NP administrator, the block holder, and the sub-
|
|||
|
block holder. Block pooling must be implemented in a manner that
|
|||
|
allows for NP within the sub-blocks. Each TN can have a different
|
|||
|
serving operator, sub-block holder, and block holder.
|
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 20]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
8.2 ITN Pooling
|
|||
|
|
|||
|
ITN pooling refers to the process whereby the number administrator
|
|||
|
assigns individual telephone numbers to operators. Using the North
|
|||
|
American example, one block of 10,000 TNs can be divided into 10,000
|
|||
|
ITNs. ITN is more commonly deployed in freephone services.
|
|||
|
|
|||
|
In ITN the block is not assigned to an operator but to a central
|
|||
|
administrator. The administrator then assigns ITNs to operators.
|
|||
|
NP administrative processes and call processing will enable proper
|
|||
|
and efficient routing.
|
|||
|
|
|||
|
|
|||
|
9. Potential Implications
|
|||
|
|
|||
|
There are three general areas of impact to IP telephony work-in-
|
|||
|
progress at IETF:
|
|||
|
|
|||
|
- Interoperation between NP in GSTN and IP telephony
|
|||
|
- NP implementation or emulation in IP telephony
|
|||
|
- Interconnection to NP administrative environment
|
|||
|
|
|||
|
A good understanding of how number portability is supported in the
|
|||
|
GSTN is important when addressing the interworking issues between
|
|||
|
IP-based networks and the GSTN. This is especially important when
|
|||
|
the IP-based network needs to route the calls to the GSTN. As shown
|
|||
|
in Section 5, there are a variety of standards with various protocol
|
|||
|
stacks for the switch-to-NPDB interface. Not only that, the
|
|||
|
national variations of the protocol standards make it very
|
|||
|
complicated to deal with in a global environment. If an entity in
|
|||
|
the IP-based network needs to query those existing NPDBs for routing
|
|||
|
number information to terminate the calls to the destination GSTN,
|
|||
|
it would be impractical, if not an impossible, job for that entity
|
|||
|
to support all those interface standards to access the NPDBs in many
|
|||
|
countries.
|
|||
|
|
|||
|
Several alternatives may address this particular problem. One
|
|||
|
alternative is to use certain entities in the IP-based networks for
|
|||
|
dealing with NP query, similar to the International Switches that
|
|||
|
are used in the GSTN to interwork different national ISUP
|
|||
|
variations. This will force signaling information associated with
|
|||
|
the calls to certain NP-capable networks in the terminating GSTN to
|
|||
|
be routed to those IP entities that support the NP functions. Those
|
|||
|
IP entities then query the NPDBs in the terminating country. This
|
|||
|
will limit the number of NPDB interfaces that certain IP entities
|
|||
|
need to support. Another alternative can be to define a "common"
|
|||
|
interface to be supported by all the NPDBs so that all the IP
|
|||
|
entities use that standardized protocol to query them. The
|
|||
|
existing NPDBs can support this additional interface, or new NPDBs
|
|||
|
can be deployed that contain the same information but support the
|
|||
|
common IP interface. The candidates for such a common interface
|
|||
|
include Lightweight Directory Access Protocol (LDAP) and SIP
|
|||
|
[SIP](e.g., using the SIP redirection capability). Certainly
|
|||
|
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 21]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
another possibility is to use interworking function to convert from
|
|||
|
one protocol to another.
|
|||
|
|
|||
|
IP-based networks can handle the domestic calls between two GSTNs.
|
|||
|
If the originating GSTN has performed NPDB query, SIP will need to
|
|||
|
transport and make use of some of the ISUP signaling information
|
|||
|
even if ISUP signaling may be encapsulated in SIP. Also, IP-based
|
|||
|
networks may perform the NPDB queries, as the N-1 carrier. In that
|
|||
|
case, SIP also needs to transport the NP related information while
|
|||
|
the call is being routed to the destination GSTN. There are three
|
|||
|
pieces of NP related information that SIP needs to transport. They
|
|||
|
are 1) the called directory number, 2) a routing number, and 3) a
|
|||
|
NPDB dip indicator. The NPDB dip indicator is needed so that the
|
|||
|
terminating GSTN will not perform another NPDB dip. The routing
|
|||
|
number is needed so that it is used to route the call to the
|
|||
|
destination network or switch in the destination GSTN. The called
|
|||
|
directory number is needed so that the terminating GSTN switch can
|
|||
|
terminate the call. When the routing number is present, the NPDB
|
|||
|
dip indicator may not be present because there are cases where
|
|||
|
routing number is added for routing the call even if NP is not
|
|||
|
involved. One issue is how to transport the NP related information
|
|||
|
via SIP. The SIP Universal Resource Locator (URL) is one mechanism.
|
|||
|
Another better choice may be to add an extension to the "tel" URL
|
|||
|
[TEL] that is also supported by SIP. Please see [TELNP] for the
|
|||
|
proposed extensions to the "tel" URL to support NP and freephone
|
|||
|
service. Those extensions to the "tel" URL will be automatically
|
|||
|
supported by SIP because they can be carried as the optional
|
|||
|
parameters in the user portion of the "sip" URL.
|
|||
|
|
|||
|
For a called directory number that belongs to a country that
|
|||
|
supports NP, and if the IP-based network is to perform the NPDB
|
|||
|
query, the logical step is to perform the NPDB dip first to retrieve
|
|||
|
the routing number and use that routing number to select the correct
|
|||
|
IP telephony gateways that can reach the serving switch that serves
|
|||
|
the called directory number. Therefore, if the "rn" parameter is
|
|||
|
present in the "tel" URL or sip URL in the SIP INVITE message, it
|
|||
|
instead of the called directory number should be used for making
|
|||
|
routing decisions assuming that no other higher priority routing-
|
|||
|
related parameters such as the <20>cic<69> are present. If "rn" is not
|
|||
|
present, then the dialed directory number can be used as the routing
|
|||
|
number for making routing decisions.
|
|||
|
|
|||
|
Telephony Routing Information Protocol (TRIP) [TRIP] is a policy
|
|||
|
driven inter-administrative domain protocol for advertising the
|
|||
|
reachability of telephony destinations between location servers, and
|
|||
|
for advertising attributes of the routes to those destinations.
|
|||
|
With the NP in mind, it is very important to know that it is the
|
|||
|
routing number, if present, not the called directory number that
|
|||
|
should be used to check against the TRIP tables for making the
|
|||
|
routing decisions.
|
|||
|
|
|||
|
Overlap signaling exists in the GSTN today. For a call routing from
|
|||
|
the originating GSTN to the IP-based network that involves overlap
|
|||
|
signaling, NP will impact the call processing within the IP-based
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 22]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
networks if they must deal with the overlap signaling. The entities
|
|||
|
in the IP-based networks that are to retrieve the NP information
|
|||
|
(e.g., the routing number) must collect a complete called directory
|
|||
|
number information before retrieving the NP information for a ported
|
|||
|
number. Otherwise, the information retrieval won't be successful.
|
|||
|
This is an issue for the IP-based networks if the originating GSTN
|
|||
|
does not handle the overlap signaling by collecting the complete
|
|||
|
called directory number.
|
|||
|
|
|||
|
The IETF enum working group is defining the use of Domain Name
|
|||
|
System (DNS) for identifying available services associated with a
|
|||
|
particular E.164 number [ENUM]. [ENUMPO] outlines the principles
|
|||
|
for the operation of a telephone number service that resolves
|
|||
|
telephone numbers into Internet domain name addresses and service-
|
|||
|
specific directory discovery. [ENUMPO] implements a three-level
|
|||
|
approach where the first level is the mapping of the telephone
|
|||
|
number delegation tree to the authority to which the number has been
|
|||
|
delegated, the second level is the provision of the requested DNS
|
|||
|
resource records from a service registrar, and the third level is
|
|||
|
the provision of service specific data from the service provider
|
|||
|
itself. NP certainly must be considered at the first level because
|
|||
|
the telephony service providers do not "own" or control the
|
|||
|
telephone numbers under the NP environment; therefore, they may not
|
|||
|
be the proper entities to have the authority for a given E.164
|
|||
|
number. Not only that, there is a regulatory requirement on NP in
|
|||
|
some countries that the donor network should not be relied on to
|
|||
|
reach the delegated authority during the DNS process . The
|
|||
|
delegated authority for a given E.164 number is likely to be an
|
|||
|
entity designated by the end user that owns/controls a specific
|
|||
|
telephone number or one that is designated by the service registrar.
|
|||
|
|
|||
|
Since the telephony service providers may have the need to use ENUM
|
|||
|
for their network-related services (e.g., map an E.164 number to a
|
|||
|
HLR Identifier in the wireless networks), their ENUM records must be
|
|||
|
collocated with those of the telephony subscribers. If that is the
|
|||
|
case, NP will impact ENUM when a telephony subscriber who has ENUM
|
|||
|
service changes the telephony service provider. This is because
|
|||
|
that the ENUM records from the new telephony service provider must
|
|||
|
replace those from the old telephony service provider. To avoid the
|
|||
|
NP impact on ENUM, it is recommended that the telephony service
|
|||
|
providers use a different domain tree for their network-related
|
|||
|
service. For example, if e164.arpa is chosen for <20>end user<65> ENUM, a
|
|||
|
domain tree different from e164.arpa should be used for <20>carrier<65>
|
|||
|
ENUM.
|
|||
|
|
|||
|
The IP-based networks also may need to support some forms of number
|
|||
|
portability in the future if E.164 numbers [E164] are assigned to
|
|||
|
the IP-based end users. One method is to assign a GSTN routing
|
|||
|
number for each IP-based network domain or entity in a NP-capable
|
|||
|
country. This may increase the number of digits in the routing
|
|||
|
number to incorporate the IP entities and impact the existing
|
|||
|
routing in the GSTN. Another method is to associate each IP entity
|
|||
|
with a particular GSTN gateway. At that particular GSTN gateway,
|
|||
|
the called directory number then is used to locate the IP-entity
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 23]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview June 24, 2002
|
|||
|
|
|||
|
that serves that dialed directory number. Yet, another method can
|
|||
|
be to assign a special routing number so that the call to an end
|
|||
|
user currently served by an IP entity is routed to the nearest GSTN
|
|||
|
gateway. The called directory number then is used to locate the IP-
|
|||
|
entity that serves that dialed directory number. A mechanism can be
|
|||
|
developed or used for the IP-based network to locate the IP entity
|
|||
|
that serves a particular dialed directory number. Many other types
|
|||
|
of networks use E.164 numbers to identify the end users or terminals
|
|||
|
in those networks. Number portability among GSTN, IP-based network
|
|||
|
and those various types of networks may also need to be supported in
|
|||
|
the future.
|
|||
|
|
|||
|
|
|||
|
10. Security Considerations
|
|||
|
|
|||
|
This document does not raise any security issues.
|
|||
|
|
|||
|
|
|||
|
11. IANA Considerations
|
|||
|
|
|||
|
This document introduces no new values for IANA registration.
|
|||
|
|
|||
|
|
|||
|
12. Normative References
|
|||
|
|
|||
|
[ANSI OSS] ANSI Technical Requirements No. 1, "Number Portability -
|
|||
|
Operator Services Switching Systems," April 1999.
|
|||
|
|
|||
|
[ANSI SS] ANSI Technical Requirements No. 2, "Number Portability -
|
|||
|
Switching Systems," April 1999.
|
|||
|
|
|||
|
[ANSI DB] ANSI Technical Requirements No. 3, "Number Portability
|
|||
|
Database and Global Title Translation," April 1999.
|
|||
|
|
|||
|
[CS1] ITU-T Q-series Recommendations - Supplement 4, "Number
|
|||
|
portability Capability set 1 requirements for service provider
|
|||
|
portability (All call query and onward routing)," May 1998.
|
|||
|
|
|||
|
[CS2] ITU-T Q-series Recommendations - Supplement 5, "Number
|
|||
|
portability -Capability set 2 requirements for service provider
|
|||
|
portability (Query on release and Dropback)," March 1999.
|
|||
|
|
|||
|
[E164] ITU-T Recommendation E.164, "The International Public
|
|||
|
Telecommunications Numbering Plan," 1997.
|
|||
|
|
|||
|
[ENUM] P. Falstrom, "E.164 number and DNS," RFC 2916.
|
|||
|
|
|||
|
[ETSIISUP] ETSI EN 302 097 V.1.2.2, <20>Integrated Services Digital
|
|||
|
Network (ISDN); Signalling System No.7 (SS7); ISDN User Part
|
|||
|
(ISUP); Enhancement for support of Number Portability (NP)
|
|||
|
[ITU-T Recommendation Q.769.1 (2000), modified]
|
|||
|
|
|||
|
[GSM] GSM 09.02: "Digital cellular telecommunications system (Phase
|
|||
|
2+); Mobile Application Part (MAP) specification".
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on December 23, 2002 [Page 24]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview March 1, 2002
|
|||
|
|
|||
|
|
|||
|
|
|||
|
[IS41] TIA/EIA IS-756 Rev. A, "TIA/EIA-41-D Enhancements for
|
|||
|
Wireless Number Portability Phase II (December 1998)"Number
|
|||
|
Portability Network Support," April 1998.
|
|||
|
|
|||
|
[ITUISUP] ITU-T Recommendation Q.769.1, "Signaling System No. 7 -
|
|||
|
ISDN User Part Enhancements for the Support of Number
|
|||
|
Portability," December 1999.
|
|||
|
|
|||
|
[MNP] ETSI EN 301 716 (2000-10) European Standard
|
|||
|
(Telecommunications series) Digital cellular telecommunications
|
|||
|
system (Phase 2+); Support of Mobile Number Portability (MNP);
|
|||
|
Technical Realisation; Stage 2; (GSM 03.66 Version 7.2.0
|
|||
|
Release 1998).
|
|||
|
|
|||
|
[RFC] Scott Bradner, RFC2026, "The Internet Standards Process --
|
|||
|
Revision 3," October 1996.
|
|||
|
|
|||
|
|
|||
|
13. Informative References
|
|||
|
|
|||
|
[ENUMPO] A. Brown and G. Vaudreuil, "ENUM Service Specific
|
|||
|
Provisioning: Principles of Operations," draft-ietf-enum-
|
|||
|
operation-02.txt, February 23, 2001.
|
|||
|
|
|||
|
[SIP] J. Rosenberg, et al., draft-ietf-sip-rfc2543bis-09.txt, "SIP:
|
|||
|
Session Initiation Protocol," February 27, 2002.
|
|||
|
|
|||
|
[TEL] H. Schulzrinne and A. Vaha-Sipila, draft-antti-rfc2806bis-
|
|||
|
04.txt, "URIs for Telephone Calls," May 24, 2002.
|
|||
|
|
|||
|
[TELNP] J. Yu, draft-yu-tel-url-05.txt, "Extensions to the "tel" URL
|
|||
|
to support Number Portability and Freephone Service," June 14,
|
|||
|
2002.
|
|||
|
|
|||
|
[TRIP] J. Rosenberg, H. Salama and M. Squire, RFC 3219, "Telephony
|
|||
|
Routing Information Protocol (TRIP)," January 2002.
|
|||
|
|
|||
|
|
|||
|
14. Acknowledgment
|
|||
|
|
|||
|
The authors would like to thank Monika Muench for providing
|
|||
|
information on ISUP and MNP.
|
|||
|
|
|||
|
|
|||
|
15. Authors' Addresses
|
|||
|
|
|||
|
Mark D. Foster
|
|||
|
NeuStar, Inc.
|
|||
|
1120 Vermont Avenue, NW,
|
|||
|
Suite 400
|
|||
|
Washington, D.C. 20005
|
|||
|
United States
|
|||
|
|
|||
|
Foster,McGarry,Yu Expired on August 31, 2002 [Page 25]
|
|||
|
|
|||
|
Number Portability in the GSTN: An Overview March 1, 2002
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Phone: +1-202-533-2800
|
|||
|
Fax: +1-202-533-2987
|
|||
|
Email: mark.foster@neustar.biz
|
|||
|
|
|||
|
Tom McGarry
|
|||
|
NeuStar, Inc.
|
|||
|
1120 Vermont Avenue, NW,
|
|||
|
Suite 400
|
|||
|
Washington, D.C. 20005
|
|||
|
United States
|
|||
|
|
|||
|
Phone: +1-202-533-2810
|
|||
|
Fax: +1-202-533-2987
|
|||
|
Email: tom.mcgarry@neustar.biz
|
|||
|
|
|||
|
James Yu
|
|||
|
NeuStar, Inc.
|
|||
|
1120 Vermont Avenue, NW,
|
|||
|
Suite 400
|
|||
|
Washington, D.C. 20005
|
|||
|
United States
|
|||
|
|
|||
|
Phone: +1-202-533-2814
|
|||
|
Fax: +1-202-533-2987
|
|||
|
Email: james.yu@neustar.biz
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Full Copyright Statement
|
|||
|
|
|||
|
"Copyright (C) The Internet Society (2002). 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. However, this
|
|||
|
document itself may not be modified in any way, such as by removing
|
|||
|
the copyright notice or references to the Internet Society or other
|
|||
|
Internet organizations, except as needed for the purpose of
|
|||
|
developing Internet standards in which case the procedures for
|
|||
|
copyrights defined in the Internet Standards process must be
|
|||
|
followed, or as required to translate it into languages other than
|
|||
|
English.
|
|||
|
|
|||
|
The limited permissions granted above are perpetual and will not be
|
|||
|
revoked by the Internet Society or its successors or assigns.
|
|||
|
|
|||
|
|
|||
|
|
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Foster,McGarry,Yu Expired on August 31, 2002 [Page 26]
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Number Portability in the GSTN: An Overview March 1, 2002
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This document and the information contained herein is provided on an
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"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Acknowledgement
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Funding for the RFC Editor function is currently provided by the
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Internet Society.
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Foster,McGarry,Yu Expired on August 31, 2002 [Page 27]
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