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diff --git a/contrib/bind9/doc/draft/draft-ietf-enum-e164-gstn-np-05.txt b/contrib/bind9/doc/draft/draft-ietf-enum-e164-gstn-np-05.txt deleted file mode 100644 index 3353b3bb423f..000000000000 --- a/contrib/bind9/doc/draft/draft-ietf-enum-e164-gstn-np-05.txt +++ /dev/null @@ -1,1588 +0,0 @@ - - Mark Foster -Internet Draft Tom McGarry -Document: <draft-ietf-enum-e164-gstn-np-05.txt> James Yu - NeuStar, Inc. -Category: Informational June 24, 2002 - - - Number Portability in the GSTN: An Overview - - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026 [RFC]. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. Internet-Drafts are draft documents valid for a maximum of - six months and may be updated, replaced, or obsoleted by other - documents at any time. It is inappropriate to use Internet- Drafts - as reference material or to cite them other than as "work in - progress." - - The list of current Internet-Drafts can be accessed at - http://www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - - Copyright Notice - - Copyright (C) The Internet Society (2002). All rights reserved. - - - Abstract - - This document provides an overview of E.164 telephone number - portability (NP) in the Global Switched Telephone Network (GSTN). - NP is a regulatory imperative seeking to liberalize local telephony - service competition, by enabling end-users to retain telephone - numbers while changing service providers. NP changes the - fundamental nature of a dialed E.164 number from a hierarchical - physical routing address to a virtual address, thereby requiring the - transparent translation of the later to the former. In addition, - there are various regulatory constraints that establish relevant - parameters for NP implementation, most of which are not network - technology specific. Consequently, the implementation of NP - behavior consistent with applicable regulatory constraints, as well - as the need for interoperation with the existing GSTN NP - implementations, are relevant topics for numerous areas of IP - telephony work-in-progress at IETF. - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 1] - -Number Portability in the GSTN: An Overview June 24, 2002 - - - Table of Contents - - 1. Introduction ............................................... 2 - 2. Abbreviations and Acronyms ................................. 4 - 3. Types of Number Portability ................................ 5 - 4. Service Provider Number Portability Schemes ................ 7 - 4.1 All Call Query (ACQ) .................................. 7 - 4.2 Query on Release (QoR) ................................ 8 - 4.3 Call Dropback ......................................... 9 - 4.4 Onward Routing (OR) ................................... 9 - 4.5 Comparisons of the Four Schemes ....................... 10 - 5. Database Queries in the NP Environment ..................... 11 - 5.1 U.S. and Canada ....................................... 12 - 5.2 Europe ................................................ 13 - 6. Call Routing in the NP Environment ......................... 14 - 6.1 U.S. and Canada ....................................... 14 - 6.2 Europe ................................................ 15 - 7. NP Implementations for Geographic E.164 Numbers ............ 17 - 8. Number Conservation Method Enabled By NP ................... 20 - 8.1 Block Pooling ......................................... 20 - 8.2 ITN Pooling ........................................... 21 - 9. Potential Implications ..................................... 21 - 10. Security Considerations .................................... 24 - 11. IANA Considerations ........................................ 24 - 12. Normative References ....................................... 24 - 13. Informative References ..................................... 25 - 14. Acknowledgement ............................................ 25 - 15. AuthorsË Addresses ......................................... 25 - - - -1. Introduction - - This document provides an overview of E.164 telephone number - portability in the Global Switched Telephone Network (GSTN). There - are considered to be three types of number portability (NP): service - provider portability (SPNP), location portability (not to be - confused with terminal mobility), and service portability. - - Service provider portability (SPNP), the focus of the present draft, - is a regulatory imperative in many countries seeking to liberalize - telephony service competition, especially local service. - Historically, local telephony service (as compared to long distance - or international service) has been regulated as a utility-like form - of service. While a number of countries had begun liberalization - (e.g. privatization, de-regulation, or re-regulation) some years - ago, the advent of NP is relatively recent (since ~1995). - - E.164 numbers can be non-geographic and geographic numbers. Non- - geographic numbers do not reveal the locations information of those - numbers. Geographic E.164 numbers were intentionally designed as - hierarchical routing addresses which could systematically be digit- - analyzed to ascertain the country, serving network provider, serving - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 2] - -Number Portability in the GSTN: An Overview June 24, 2002 - - end-office switch, and specific line of the called party. As such, - without NP a subscriber wishing to change service providers would - incur a number change as a consequence of being served off of a - different end-office switch operated by the new service provider. - The cost and convenience impact to the subscriber of changing - numbers is seen as barrier to competition. Hence NP has become - associated with GSTN infrastructure enhancements associated with a - competitive environment driven by regulatory directives. - - Forms of SPNP have been deployed or are being deployed widely in the - GSTN in various parts of the world, including the U.S., Canada, - Western Europe, Australia, and the Pacific Rim (e.g. Hong Kong). - Other regions, such as South America (e.g. Brazil) are actively - considering it. - - Implementation of NP within a national telephony infrastructure - entails potentially significant changes to numbering administration, - network element signaling, call routing and processing, billing, - service management, and other functions. - - NP changes the fundamental nature of a dialed E.164 number from a - hierarchical physical routing address to a virtual address. NP - implementations attempt to encapsulate the impacts to the GSTN and - make NP transparent to subscribers by incorporating a translation - function to map a dialed, potentially ported E.164 address, into a - network routing address (either a number prefix or another E.164 - address) which can be hierarchically routed. - - This is roughly analogous to the use of network address translation - on IP addresses to enable IP address portability by containing the - impact of the address change to the edge of the network and retain - the use of CIDR blocks in the core which can be route aggregated by - the network service provider to the rest of the internet. - - NP bifurcates the historical role of a subscriberËs E.164 address - into two or more data elements (a dialed or virtual address, and a - network routing address) that must be made available to network - elements through an NP translations database, carried by forward - call signaling, and recorded on call detail records. Not only is - call processing and routing affected, but also so is SS7/C7 - messaging. A number of TCAP-based SS7 messaging sets utilize an - E.164 address as an application-level network element address in the - global title address (GTA) field of the SCCP message header. - Consequently, SS7/C7 signaling transfer points (STPs) and gateways - need to be able to perform n-digit global title translation (GTT) to - translate a dialed E.164 address into its network address - counterpart via the NP database. - - In addition, there are various national regulatory constraints that - establish relevant parameters for NP implementation, most of which - are not network technology specific. Consequently, implementations - of NP behavior in IP telephony consistent with applicable regulatory - constraints, as well as the need for interoperation with the - - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 3] - -Number Portability in the GSTN: An Overview June 24, 2002 - - existing GSTN NP implementations, are relevant topics for numerous - areas of IP telephony work-in-progress at IETF. - - This document describes three types of number portability and the - four schemes that have been standardized to support SPNP for - geographic E.164 numbersspecifically. Following that, specific - information regarding the call routing and database query - implementations are described for several regions (North American - and Europe) and industries (wireless vs. wireline). The Number - Portability Database (NPDB) interfaces and the call routing schemes - that are used in the North America and Europe are described to show - the variety of standards that may be implemented worldwide. A - glance of the NP implementations worldwide is provided. Number - pooling is briefly discussed to show how NP is being enhanced in the - U.S. to conserve North American area codes. The conclusion briefly - touches the potential impacts of NP on IP & Telecommunications - Interoperability. Appendix A provides some specific technical and - regulatory information on NP in North America. Appendix B describes - the number portability administration process that manages the - number portability database in North America. - - -2. Abbreviations and Acronyms - - ACQ All Call Query - AIN Advanced Intelligent Network - AMPS Advanced Mobile Phone System - ANSI American National Standards Institute - CDMA Code Division Multiple Access - CdPA Called Party Address - CdPN Called Party Number - CH Code Holder - CMIP Common Management Information Protocol - CS1 Capability Set 1 - CS2 Capability Set 2 - DN Directory Number - DNS Domain Name System - ETSI European Technical Standards Institute - FCI Forward Call Indicator - GAP Generic Address Parameter - GMSC Gateway Mobile Services Switching Center or Gateway Mobile - Switching Center - GSM Global System for Mobile Communications - GSTN Global Switched Telephone Network - GW Gateways - HLR Home Location Register - IAM Initial Address Message - IETF Internet Engineering Task Force - ILNP Interim LNP - IN Intelligent Network - INAP Intelligent Network Application Part - INP Interim NP - IP Internet Protocol - IS-41 Interim Standards Number 41 - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 4] - -Number Portability in the GSTN: An Overview June 24, 2002 - - ISDN Integrated Services Digital Network - ISUP ISDN User Part - ITN Individual Telephony Number - ITU International Telecommunication Union - ITU-TS ITU-Telecommunication Sector - LDAP Lightweight Directory Access Protocol - LEC Local Exchange Carrier - LERG Local Exchange Routing Guide - LNP Local Number Portability - LRN Location Routing Number - MAP Mobile Application Part - MNP Mobile Number Portability - MSRN Mobile Station Roaming Number - MTP Message Transfer Part - NANP North American Numbering Plan - NP Number Portability - NPDB Number Portability Database - NRN Network Routing Number - OR Onward Routing - OSS Operation Support System - PCS Personal Communication Services - PNTI Ported Number Translation Indicator - PODP Public Office Dialing Plan - PUC Public Utility Commission - QoR Query on Release - RN Routing Number - RTP Return to Pivot - SCCP Signaling Connection Control Part - SCP Service Control Point - SIP Session Initiation Protocol - SMR Special Mobile Radio - SMS Service Management System - SPNP Service Provider Number Portability - SRF Signaling Relaying Function - SRI Send Routing Information - SS7 Signaling System Number 7 - STP Signaling Transfer Point - TCAP Transaction Capabilities Application Part - TDMA Time Division Multiple Access - TN Telephone Number - TRIP Telephony Routing Information Protocol - URL Universal Resource Locator - U.S. United States - - -3. Types of Number Portability - - As there are several types of E.164 numbers (telephone numbers, or - just TN) in the GSTN, there are correspondingly several types of - E.164 NP in the GSTN. First there are so-call non-geographic E.164 - numbers, commonly used for service-specific applications such as - freephone (800 or 0800). Portability of these numbers is called - non-geographic number portability (NGNP). NGNP, for example, was - deployed in the U.S. in 1986-92. - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 5] - -Number Portability in the GSTN: An Overview June 24, 2002 - - - Geographic number portability, which includes traditional fixed or - wireline numbers as well as mobile numbers which are allocated out - of geographic number range prefixes, is called NP or GNP or in the - U.S. local number portability (LNP). - - Number portability allows the telephony subscribers in the Global - Switched Telephone Network (GSTN) to keep their phone numbers when - they change their service providers or subscribed services, or when - they move to a new location. - - The ability to change the service provider while keeping the same - phone number is called service provider portability (SPNP) also - known as "operator portability." - - The ability to change the subscriberËs fixed service location while - keeping the same phone number is called location portability. - - The ability to change the subscribed services (e.g., from the plain - old telephone service to Integrated Services Digital Network (ISDN) - services) while keeping the same phone number is called service - portability. Another aspect of service portability is to allow the - subscribers to enjoy the subscribed services in the same way when - they roam outside their home networks as is supported by the - cellular/wireless networks. - - In addition, mobile number portability (MNP) refers to specific NP - implementation in mobile networks either as part of a broader NP - implementation in the GSTN or on a stand-alone basis. Where - interoperation of LNP and MNP is supported, service portability - between fixed and mobile service types is possible. - - At present, SPNP has been the primary form of NP deployed due to its - relevance in enabling local service competition. - - Also in use in the GSTN are the terms interim NP (INP) or Interim - LNP (ILNP) and true NP. Interim NP usually refers to the use of - remote call forwarding-like measures to forward calls to ported - numbers through the donor network to the new service network. These - are considered interim relative to true NP, which seeks to remove - the donor network or old service provider from the call or signaling - path altogether. Often the distinction between interim and true NP - is a national regulatory matter relative to the - technical/operational requirements imposed on NP in that country. - - Implementations of true NP in certain countries (e.g. U.S., Canada, - Spain, Belgium, Denmark) may pose specific requirements for IP - telephony implementations as a result of regulatory and industry - requirements for providing call routing and signaling independent of - the donor network or last previous serving network. - - - - - -Foster,McGarry,Yu Expired on December 23, 2002 [Page 6] - -Number Portability in the GSTN: An Overview June 24, 2002 - - -4. Service Provider Number Portability Schemes - - Four schemes can be used to support service provider portability and - are briefly described below. But first, some further terms are - introduced. - - The donor network is the network that first assigned a telephone - number (e.g., TN +1-202-533-1234) to a subscriber, out of a number - range administratively (e.g., +1 202-533) assigned to it. The - current service provider (new SP) or new serving network is the - network that currently serves the ported number. The old serving - network (or old SP) is the network that previously served the ported - number before the number was ported to the new serving network. - Since a TN can port a number of times, the old SP is not necessarily - the same as the donor network, except for the first time the TN - ports away, or if the TN ports back into the donor network and away - again. While the new SP and old SP roles are transitory as a TN - ports around, the donor network is always the same for any - particular TN based on the service provider to whom the subtending - number range was administratively assigned. See the discussion - below on number pooling, as this enhancement to NP further - bifurcates the role of donor network into two (the number range or - code holder network, and the block holder network). - - To simplify the illustration, all the transit networks are ignored, - the originating or donor network is the one that performs the - database queries or call redirection, and the dialed directory - number (TN) has been ported out of the donor network before. - - It is assumed that the old serving network, the new serving network - and the donor network are different networks so as to show which - networks are involved in call handling and routing and database - queries in each of four schemes. Please note that the port of the - number (process of moving it from one network to another) happened - prior to the call setup and is not included in the call steps. - Information carried in the signaling messages to support each of the - four schemes is not discussed to simplify the explanation. - - -4.1 All Call Query (ACQ) - - Figure 1 shows the call steps for the ACQ scheme. Those call steps - 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 - Ÿportable÷ 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 ŸN-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 Ÿcic÷ 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 Ÿend user÷ ENUM, a - domain tree different from e164.arpa should be used for Ÿcarrier÷ - 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, ŸIntegrated 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). 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