ENUM Working Group A. Gallant Internet Draft Comsat Corporation Expires: January 6, 2001 July 7, 2000 The Number Portability Supplement to ITU-T Recommendation E.164 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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. 1. Abstract This document contains a text version of the Number Portability Supplement (11/98) to ITU-T Recommendation E.164 (The international public telecommunication numbering plan, 05/97) [2]. That Supplement [3] defined terminology for number portability within an E.164 numbering scheme; identified formats, call flows, architectures, and routing approaches for some methods; and gave examples of some processes needed to implement number portability. A January 2000 workshop on IP-Telecomms interworking (focused on numbering, naming, addressing, and routing) identified issues to be addressed by the IETF and/or the ITU [4]. This Supplement was noted as a document related to a joint IETF/ITU issue on E.164 number portability. A text version was posted on the ITU's web site in March 2000 and notified to the itu+ietf and enum mailing lists. This Internet Draft is being submitted to support work of the ENUM (Telephone Number Mapping) Working Group on impacts of local number portability on a DNS-based architecture and protocols for mapping a telephone number to a set of attributes (e.g., URLs) [5]. Gallant Expires January 6, 2001 1 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 2. Convention used in this document "e164s2" below flags the section numbering from the ITU original. 3. Table of Contents Status of this Memo . . . . . . . . . . . . . . . . . . . . . . . 1 1. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Convention Used in this Document . . . . . . . . . . . . . . . 2 3. Table of Contents . . . . . . . . . . . . . . . . . . . . . . 2 4. Text Version of the Number Portability Supplement . . . . . . 3 (e164s2) 1 Scope . . . . . . . . . . . . . . . . . . . . . . . . 3 (e164s2) 2 References . . . . . . . . . . . . . . . . . . . . . . 3 (e164s2) 3 Definitions and abbreviations . . . . . . . . . . . . 3 (e164s2) 4 E.164 number structures . . . . . . . . . . . . . . . 6 (e164s2) 4.1 International public telecommunication number for geographic areas . . . . . . . . . . . . . . . . . . 7 (e164s2) 4.2 International public telecommunication number for global services . . . . . . . . . . . . . . . . . . 7 (e164s2) 4.3 International public telecommunication number for networks . . . . . . . . . . . . . . . . . . . . . . 8 (e164s2) 5 Number portability types . . . . . . . . . . . . . . . 8 (e164s2) 6 Generic implementation of number portability . . . . . 11 (e164s2) 7 Entities addressed by routing . . . . . . . . . . . . 12 (e164s2) 8 Number portability mechanisms . . . . . . . . . . . . 13 (e164s2) 8.1 Assumptions . . . . . . . . . . . . . . . . . . . . 13 (e164s2) 8.2 General description . . . . . . . . . . . . . . . . 13 (e164s2) 9 Types of addresses and numbers _ within networks and across network boundaries . . . . . . . . . . . . . . 18 (e164s2) 9.1 Concatenated address . . . . . . . . . . . . . . . . 19 (e164s2) 9.2 Separated addresses . . . . . . . . . . . . . . . . 21 (e164s2) 9.3 RN only . . . . . . . . . . . . . . . . . . . . . . 22 (e164s2) 9.4 Only DN (normally across network boundaries) . . . . 22 (e164s2) 10 Combinations of addressing types, addressed entities and mechanisms: general signalling requirements . . . 23 (e164s2) 11 Examples of locations of number portability database(s) within networks . . . . . . . . . . . . . 24 (e164s2) 12 Administrative processes . . . . . . . . . . . . . . 25 5. Front Matter from the ITU-T Published Version . . . . . . . . 26 6. Security Considerations . . . . . . . . . . . . . . . . . . . 27 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 9. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 28 10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 28 Gallant Expires January 6, 2001 2 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 4. Text Version of the Number Portability Supplement This section contains the text of the Rec. E.164 Supplement on Number Portability. It also contains text versions of all figures and tables. The front matter of the ITU-T published version is found in Section 6 of this document. -------------------------------------------------------------------- SUPPLEMENT 2 to Recommendation E.164 (The international public telecommunication numbering plan) Number Portability (Geneva, 1998) (e164s2) 1 Scope This Supplement defines standard terminology for a common understanding of the different aspects of number portability within an E.164 numbering scheme. It identifies numbering and addressing formats, call flows, network architectures and routing approaches that will provide alternative methods of implementation. It also proposes some examples of the administrative and operational processes required for the successful implementation of number portability. (e164s2) 2 References - ITU-T Recommendation E.164 (1997), The international public telecommunication numbering plan. (e164s2) 3 Definitions and abbreviations (e164s2) 3.1 Definitions The following definitions and terms used in this Supplement are to be used within the context of number portability. (e164s2) 3.1.1 address (taken from E.164): A string or combination of decimal digits, symbols and additional information which identifies the specific termination point(s) of a connection in a public network(s) or, where applicable, in interconnected private network(s). (e164s2) 3.1.2 directory number: See end user's number. (e164s2) 3.1.3 donor network/exchange: The initial network/exchange where a number was located before ever being ported. (e164s2) 3.1.4 donor service provider: The service provider from whom the number was initially ported. Gallant Expires January 6, 2001 3 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 3.1.5 end user's number: The E.164 number used by the calling party to establish a call to the end user. This number is also used for presentation services like Calling Line Identification (CLI) and Connected Line Identification Presentation (COLP). The end user's number is equivalent to a directory number. (e164s2) 3.1.6 Geographic Number (GN): An E.164 number which corresponds to a discrete geographic area. (e164s2) 3.1.7 location portability: The ability of an end user to retain the same E.164 international public telecommunication number when moving from one location to another. (e164s2) 3.1.8 network operator: An entity that operates a network in order to route calls. (e164s2) 3.1.9 Non-Geographic Number (NGN): An E.164 number which has no geographic significance. (e164s2) 3.1.10 numbering plan: A numbering plan specifies the format and structure of the numbers used within that plan. It typically consists of decimal digits segmented into groups in order to identify specific elements used for identification, routing and charging capabilities, e.g. within E.164 to identify countries, national destinations and subscribers. A numbering plan does not include prefixes, suffixes and additional information required to complete a call. The national numbering plan is the national implementation of the E.164 numbering plan. (e164s2) 3.1.11 originating network/exchange: The network/exchange serving a calling end user. (e164s2) 3.1.12 portable number: An entire E.164 number identified by an appropriate authority which is subject to number portability. (e164s2) 3.1.13 ported number: An end user's E.164 number that has been subject to number portability. (e164s2) 3.1.14 recipient network/exchange: The network/exchange where a number is located after being ported. [Footnote: The recipient exchange may consist of a central processor and both co- located and remote concentrator units. The routing number may identify either this whole ensemble or a specific concentrator (in which case the ensemble may use several different routing numbers).] Gallant Expires January 6, 2001 4 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 3.1.15 recipient service provider: The service provider to whom the number is ported. (e164s2) 3.1.16 routing number: A number that is derived and used by the network to route the call towards a ported number. Four types of entities can be indicated by routing numbers as follows: - Recipient network: The routing number identifies the network where the customer is now located. Therefore the routing process will need additional information (i.e. DN) to be completed. - Recipient exchange: The routing number identifies the exchange where the customer is now located. Therefore the routing process within the recipient exchange will need additional information (i.e. DN) to be completed. - Point of interconnection: The routing number identifies an interface to the next network in the routing process. Therefore the routing process will need additional information (i.e. DN) to be completed. - Network termination point: The routing number identifies the subscriber/access line/service. The ported customer identified by the RN is unique. Therefore the routing process in terms of number portability can be completed without any additional information. (e164s2) 3.1.17 serving network(s)/exchange(s): The network(s)/exchange(s) that determines the status of a number in an environment capable of supporting number portability and, if necessary, obtains the routing information for ported numbers. The functionality to provide these capabilities may reside in either the originating, donor, recipient or transit network/exchange or in some combination. (e164s2) 3.1.18 service number: A non-geographic E.164 number allocated to a specific category of services. (e164s2) 3.1.19 service portability: The ability of an end user to retain the same E.164 international public telecommunication number when changing from one type of service to another. (e164s2) 3.1.20 service provider: An entity that offers services to users involving the use of network resources. (e164s2) 3.1.21 service provider portability: The ability of an end user to retain the same E.164 international public telecommunication number when changing from one service provider to another. Gallant Expires January 6, 2001 5 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 3.1.22 service provider portability for geographic numbers: The ability of an end user to retain the same geographic E.164 international public telecommunication number when changing from one service provider to another without changing their location and without changing the nature of the service offered. (e164s2) 3.1.23 service provider portability for non-geographic numbers: The ability of an end user to retain the same non- geographic E.164 international public telecommunications number when changing from one service provider to another without changing the nature of the service offered. (e164s2) 3.1.24 transit network(s)/exchange(s): A network/exchange between two networks. (e164s2) 3.2 Abbreviations CCBS Completion of Calls to Busy Subscriber DDI Direct-Dialling-In DN Directory Number GNP Geographic Number Portability IN Intelligent Network MSN Multiple Subscriber Number NGNP Non-Geographic Number Portability RN Routing Number SP Service Provider (e164s2) 4 E.164 number structures This clause identifies three different structures for the international public telecommunication number: - international public telecommunication number for geographic areas; - international public telecommunication number for global services; - international public telecommunication number for networks. Gallant Expires January 6, 2001 6 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 4.1 International public telecommunication number for geographic areas +-------------+ +-----------------+ +---------------------+ | CC | | NDC | | SN | +-------------+ +-----------------+ +---------------------+ | | | | |1 to 3 digits| | Max (15-n) digits | | | | | | |<-----National (significant) number----->| | | |<---------------------Max 15 digits--------------------->| | | |<--------International public telecommunication--------->| | number for geographic areas | CC Country Code for geographic areas NDC National Destination Code (optional) SN Subscriber Number n Number of digits in the country code NOTE - National and international prefixes are not part of the international public telecommunication number for geographic areas. Figure 1 - International public telecommunication number structure for geographic areas (e164s2) 4.2 International public telecommunication number for global services +-------------+ +-----------------------------------------+ | CC | | GSN | +-------------+ +-----------------------------------------+ | | | | | 3 digits | |<-------------Max 12 digits------------->| | | | | |<---------------------Max 15 digits--------------------->| | | |<--------International public telecommunication--------->| | number for global services | CC Country Code for global services GSN Global Subscriber Number NOTE - National and international prefixes are not considered to be part of the international public telecommunication number for global services. Figure 2 - International public telecommunication number structure for global services Gallant Expires January 6, 2001 7 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 4.3 International public telecommunication number for networks +-------------+ +-----------------+ +---------------------+ | CC | | IC | | SN | +-------------+ +-----------------+ +---------------------+ | | | | | | | 3 digits | | 1 to 4 digits | | Max (12-x) digits | | | | | | |<-------------Max 12 digits------------->| | | |<---------------------Max 15 digits--------------------->| | | |<--------International public telecommunication--------->| | number for networks | CC Country Code for networks IC Identification Code SN Subscriber Number x Number of digits in Identification Code (IC) NOTE - National and international prefixes are not part of the international public telecommunication number for networks. Figure 3 - International public telecommunication number structure for networks (e164s2) 5 Number portability types An E.164 number is classified into the following three types of country codes: 1) beginning with CC for geographic areas; 2) beginning with CC for global services; and 3) beginning with CC for networks. The following tables provide an overview of the applicability of each type of portability, when considered against the three number types. Gallant Expires January 6, 2001 8 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Table 1 - Service provider portability +---------------------------------------------------------+ | Scope | | | |-----------| | | |CC type | Between CC domains | Within CC domains | | (Note 1) | | | |-----------+-----------+----------+-----------+----------| |Geographic |Porting |Standards |Porting |Standards | | |not |not |applicable |not | | |applicable |required | |required | | | | | | (Note 4) | |-----------+-----------+----------+-----------+----------| |Global |Porting |Standards |Porting |Standards | |Services |not |not |applicable |not | | |applicable |required | |required | | | | | | (Note 2) | |-----------+-----------+----------+-----------+----------| |Network |Porting |Standards |Network |Network | | (Note 3) |not |not |operator |operator | | |applicable |required |matter |matter | +---------------------------------------------------------+ Table 2 - Service portability +---------------------------------------------------------+ | Scope | | | |-----------| | | |CC type | Between CC domains | Within CC domains | | (Note 1) | | | |-----------+-----------+----------+-----------+----------| |Geographic |Porting |Standards |Porting |Standards | | |not |not |applicable |not | | |applicable |required | |required | | | | | | (Note 4) | |-----------+-----------+----------+-----------+----------| |Global |Porting |Standards |Porting |Standards | |Services |not |not |not |not | | |applicable |required |applicable |required | |-----------+-----------+----------+-----------+----------| |Network |Porting |Standards |Network |Network | | (Note 3) |not |not |operator |operator | | |applicable |required |matter |matter | +---------------------------------------------------------+ Gallant Expires January 6, 2001 9 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Table 3 - Location portability +---------------------------------------------------------+ | Scope | | | |-----------| | | |CC type | Between CC domains | Within CC domains | | (Note 1) | | | |-----------+-----------+----------+-----------+----------| |Geographic |Porting |Standards |Porting |Standards | | |not |not |applicable |not | | |applicable |required | |required | | | | | | (Note 4) | |-----------+-----------+----------+-----------+----------| |Global |Porting |Standards |Porting |Standards | |Services |not |not |applicable |not | | |applicable |required | (Note 5) |required | |-----------+-----------+----------+-----------+----------| |Network |Porting |Standards |Network |Network | | (Note 3) |not |not |operator |operator | | |applicable |required |matter |matter | +---------------------------------------------------------+ Notes to Tables 1, 2 and 3: NOTE 1 - Portability not supported between CC types. NOTE 2 - Requires international agreement(s) and infrastructure to support number portability (e.g. UIFN). NOTE 3 - Includes the CC + IC digits required to uniquely identify the network. NOTE 4 - International standardization not required but could be of use. NOTE 5 - These resources are "non-geographic" therefore location portability is inherent. NOTE 6 - For purposes of Tables 1, 2 and 3, "Standards" means ITU-T Recommendations. Gallant Expires January 6, 2001 10 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 6 Generic implementation of number portability The following general routing scheme is assumed as the routing model for calls routed to a ported customer. incoming call | 1st step of the | routing process, | based on dialled digits | | +---------------------------+ +--------------------+ | Serving Network | | | Transit Network | | v | | (optional) | | +-+ | | | | | | |-------------------+ | | Serving Exchange +-+ | | | | +---------------------------+ +---------------|----+ | 2nd step of the | routing process, | based on routing number | v +---------------------------+ | Recipient Network | | | v | | +-+ | | | | | | Recipient Exchange +-+ | +---------------------------+ | | +---+ customer with | | ported number | | +---+ NOTE - The serving network may be the originating network and/or the donor or a transit network. Figure 4 - Conceptual framework for incoming calls NOTE 1 - The caller sets up the call by dialling the end user's number which in this case is a ported number. The end user's number is enough to initiate the routing process. Furthermore, number portability, by definition, implies that the callers should continue to dial the same end user's number and nothing more to set up a call to a ported customer. Gallant Expires January 6, 2001 11 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 NOTE 2 - The routing process is split into two consecutive main steps: a) Normal routing based on end user's number towards a serving exchange: As a 1st step in the routing process, the originating network routes the call up to a serving exchange clearly identified by the analysis of a certain number of leading digits of the end user's number. b) Routing to customer's interface based on routing number(s) obtained by this serving exchange: It should be noted that this step might be subdivided into sub-steps (e.g. the serving exchange could provide information to route to a database - within the recipient network or accessed by the recipient network - which provides subsequent routing information identifying the recipient exchange, information used for a subsequent sub- step in the routing process). NOTE 3 - If only the recipient network is identified, then it is the responsibility of the recipient network to terminate the call at the recipient exchange. NOTE 4 - The internal routing process in the recipient exchange shall unambiguously determine the called customer's interface and complete the call taking into account the supplementary services activated. NOTE 5 - If a number is ported subsequently from service provider No. 1 to service provider No. 2, then to service provider No. 3, etc. this will change the routing number but not the routing principles. (e164s2) 7 Entities addressed by routing Entities which need to be addressed by a Routing Number (RN) in one or more routing solutions are identified in this clause. According to the structure of the routing number, one or a combination of several of the following entities should be addressable: - A recipient network: In this option, the routing number identifies the network where the customer is now located. Therefore the routing process will need additional information (i.e. DN) to be completed. Gallant Expires January 6, 2001 12 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 - A Point of Interconnection (POI): In this option, the routing number identifies an interface to the next network in the routing process. Therefore the routing process will need additional information (i.e. DN) to be completed. - Recipient exchange: In this option, the routing number identifies the exchange where the customer is now located. Therefore the routing process within the recipient exchange will need an additional information (i.e. DN) to be completed. - Network Termination Point (NTP): In this option, the routing number identifies the subscriber/access line/service. The ported customer identified by the RN is unique. Therefore the routing process, in terms of number portability, can be completed without any additional information. (e164s2) 8 Number portability mechanisms (e164s2) 8.1 Assumptions The following document internal assumptions that have been made: a) that Calling Line Identification (CLI) is required to be transported, with display information, unchanged to recipient network; b) that Connected Line Identification (COLI) is required to be transported, with display information, unchanged to originating network; c) that initial routing arrangements have been defined and implemented prior to the introduction of routing based on a routing number; d) that number portability is not allowed to influence the carrier selection function; e) that an NP solution shall not influence functions in PBXs. (e164s2) 8.2 General description (e164s2) 8.2.1 Call rerouted from donor network by use of onward routing principles The first step/solution discussed for number portability is often that the donor network maintains the portability information, i.e. the complete address to both recipient network and exchange, for ported-out numbers and reroutes incoming calls to ported-out numbers onward towards the recipient network according to onward routing principles outlined in Figure 5. Gallant Expires January 6, 2001 13 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Originating Transit Donor Network Network(s)(A) Network +-------+ +-------+ +-------+ | | IAM | | IAM | +--+| +-->| |------>| |------>| |DB||..... | | | | | | +--+| . | +-------+ +-------+ +-------+ . | | | . Calling a1)IAM | |b)IAM . Subscriber +---------+ | . | | Called | | Subscriber v v ^ +-------+ +-------+ | | |a2)IAM | | | | |------>| |----+ | | | | +-------+ +-------+ Transit Recipient Network(s)(B) Network Figure 5 - Call rerouting to recipient network by onward routing principles from donor network In Figure 5, the donor network receives an incoming call. It then detects that the called number has been ported-out to another network and makes a DB query to retrieve a routing number. It thereafter reroutes the call onward towards the recipient network using retrieved routing information. Please note that the transit network(s) are optional, i.e. direct interconnections connections between originating network and donor network might exist and the same also between donor network and recipient network. Note also that the transit network(s) A and B can be the same depending on network structure and call case. (e164s2) 8.2.2 Call rerouted by dropback principles from donor network One possible enhancement of the previously described onward routing solution, is that the donor network initiates the rerouting of the call towards the recipient network according to "dropback" principles outlined in Figure 6. Also, in this scenario, only the donor network maintains NP information, i.e. the complete address to both recipient network and exchange, for ported-out numbers. Gallant Expires January 6, 2001 14 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Originating Transit Donor Network Network(s)(A) Network +-------+ +-------+ +-------+ | | IAM | | IAM | +--+| +-->| |------>| |......>| |DB||..... | | | | |<......| +--+| . | +-------+ +-------+ Dropb.+-------+ . | | | . Calling a1)IAM| | b)IAM . Subscriber | +---------+ . | | Called | | Subscriber ----> v v ^ Lasting +-------+ +-------+ | relation | |a2)IAM | | | ....> | |------>| |----+ Temporary | | | | relation +-------+ +-------+ Transit Recipient Network(s)(B) Network Figure 6 - Dropback with rerouting information and onward rerouting performed by a transit network The option b) is valid when direct interconnection exists between transit network A and recipient network. A further evolution is that the dropback indication is sent back to the originating network. This is mainly of interest if the originating network has direct interconnections to other networks than the transit network used in the call attempt to the donor network. The dropback indication is also passed through to the originating network if either the transit network A has no "dropback" capability or determines that the preceding network has "dropback" capability. The originating network, at reception of the release, reroutes the call towards recipient network. Please note that the transit networks are optional (i.e. direct connections between originating network and donor network might exist) but might exist [case a1) and a2)] between the onward routing (transit or originating) network and recipient network. When carrier selection is valid for the call, the originating network reuses the carrier selection information after reception of dropback indication. It could be debated if a selected carrier (e.g. TN A) is allowed/recommended to transport the dropback to originating network, but it has no option if it has no redirect on "dropback" capability. Gallant Expires January 6, 2001 15 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 8.2.3 Call rerouting initiated by "Query on Release (QoR)" principles from donor network A similar case as the previously described "dropback" principle is when the preceding network to donor initiates NP actions, i.e. an NP DB query, at reception of a release message. This case is often referred to as "Query on Release (QoR)". In Figure 7, the donor network receives an incoming call. It then detects that the called number has been ported out to another network. It then determines that one of the preceding networks has QoR capability by looking at received signalling information. It thereafter releases the call with a special indication telling that called number is ported out. The transit network then traps the release, determines that preceding network has no QoR capability, makes an NP database query and reroutes the call onward towards the recipient network. In this scenario the transit network has access to an NP DB with the complete address to the recipient network, at least for ported-out numbers. Options a1) and a2), in Figure 7, are valid when transit network A either has no direct interconnection to recipient network or when overflow traffic is placed via transit network B. Originating Transit Donor Network Network(s)(A) Network +-------+ +-------+ +-------+ | | IAM | +--+| IAM | | +-->| |------>| |DB||......>| |..... | | | | +--+|<......| | . | +-------+ +-------+ REL +-------+ . | | | . Calling a1)IAM| | b)IAM . Subscriber | +---------+ . | | Called | | Subscriber ----> v v ^ Lasting +-------+ +-------+ | relation | |a2)IAM | | | ....> | |------>| |----+ Temporary | | | | relation +-------+ +-------+ Transit Recipient Network(s)(B) Network Figure 7 - Query on Release by transit network Gallant Expires January 6, 2001 16 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 The option b), in Figure 7, is valid when direct interconnection exists between transit network A and recipient network. Please note in this case that the DB query might take place also in the originating network, i.e. that the DB could also exist in the originating network. That is what may occur if either the transit network A has no QoR query capability or determines that the preceding network has QoR capability. It therefore lets the release pass through to originating network. The originating network, at reception of the release, queries its NP database and reroutes the call towards recipient network. In this scenario the originating network has access to an NP DB with the complete address to both recipient network and exchange, at least for ported-out numbers. Sending back the release message to the originating network is also of interest if the originating network has direct connections to networks other than the transit network currently used. When carrier selection is valid for the call, the originating network reuses the carrier selection information after querying NP DB. It could be debated if a selected carrier is allowed/recommended to transport the release message to originating network, but it has no option if it has no redirect on QoR capability. (e164s2) 8.2.4 Routing initiated by "All call query" principles In the scenario shown in Figure 8, the originating network has access to an NP DB with the complete address to the recipient exchange, at least for ported-out numbers. This implies that only one NP DB look-up needs to be performed to complete the call. Note however, that more than one DB look-up may be required if there is not sufficient information to route to the recipient exchange. Gallant Expires January 6, 2001 17 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Originating Transit Donor Network Network Network +-------+ +-------+ +-------+ | +--+|a1)IAM | | | | +-->| |DB||------>| | | |..... | | +--+| | | | | . | +-------+ +-------+ +-------+ . | | | . Calling | | a2)IAM . Subscriber +---------+ +---------+ . | | Called | | Subscriber ----> | v ^ Lasting | b)IAM +-------+ | relation +------------->| | | ....> | |----+ Temporary | | relation +-------+ Recipient Network Figure 8 - All call query by originating network As can be seen in Figure 8, the donor network is not involved in the call set-up at all, however optionally the transit network [see cases a1) and a2) above] might be transiting the call to the recipient network. Alternatively, a transit network, rather than the originating network, could perform the NP DB look-up. (e164s2) 9 Types of addresses and numbers - within networks and across network boundaries With service provider portability it may no longer be possible to use an end user's number, dialled by the calling party, to route the call to the customer. If a customer changes service provider, a Routing Number (RN) is needed to be able to route the call. The routing information may have one of the following: - concatenated address (see 9.1); - separated address (see 9.2); - RN only, i.e. a plain network address, suppressed E.164 number (see 9.3); - DN only, i.e. a plain E.164 number (see 9.4). Gallant Expires January 6, 2001 18 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 9.1 Concatenated address (e164s2) 9.1.1 Description In this type of address, two numbers are concatenated in the same signalling field (the called party number) which is used to route the call (Figure 9). +-----------------------+-----------------------+ | RN | DN | +-----------------------+-----------------------+ Figure 9 - Showing a concatenated address RN is a routing number prefixed for a routing purpose. The length of RN may vary from country to country. If some non-ported numbers have DN leading digits identical to the RN, this may imply a signalling field exists which indicates "Routing information for a ported number"; otherwise, the routing would be ambiguous. The RN could take one of the following values: Case 1: RN represents the first digits of a number block usually handled by the addressed entity to which the call has to be routed. In this case, specific information carried by the signalling protocol is needed to indicate that it is a call to a ported number. Case 2: One or more of the first digits of the RN are digits not used as first digits in the national numbering plan used to indicate that the call is to a ported number. The value of the digits could be between 0 and 9 (spare in the national numbering plan). The rest of the RN identifies the addressed entity to which the call has to be routed and is used for this purpose. Case 3: This case is similar to case 2, but the first (or first two) digit(s) of the RN field is (are) one of the hexadecimal values nationally spare in the Signalling System No. 7. RN is used to route the call to the addressed entity. (e164s2) 9.1.2 Brief analysis Case 1 Pros: This solution does not waste any numbering resource since the RN value is formed by the first digits of the number block usually handled by the addressed entity. Gallant Expires January 6, 2001 19 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 This solution does not need a specific addressing scheme (for identifying the addressed exchange) and can be accommodated in the existing signalling. Cons: This solution requires the use of a specific identifier to qualify the routing number as an address used for a ported call which requires special treatment. The routing mechanisms in exchanges have to be adapted to be able to provide this special treatment. As there is a constraint on the maximum length of the complete concatenated address, the numbering space available for RN may be insufficient; limitations can be present on the maximum numbers of digits being supported by the signalling system and the exchanges in the different networks involved. Case 2 Pros: As for case 1, this solution can also be accommodated in the existing signalling. In opposition to case 1, this solution does not require any additional information to qualify the call as a ported call since one of the first digits of the routing number is dedicated to ported calls. Cons: This solution makes use of a part of the national numbering scheme. To be able to handle the prefix, routing mechanisms in the exchanges will have to be changed. As there is a constraint on the maximum length of the complete concatenated address, the numbering space available for RN may be insufficient. Case 3 Pros: This solution does not waste any resource from the national numbering plan since the first digit(s) is (are) hexadecimal. [Footnote: That is, one of the 6 values A, B, C, D, E or F.] The advantages are similar to those already mentioned for case 2. Gallant Expires January 6, 2001 20 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Cons: The drawbacks are similar to those already mentioned for case 2. However, since this solution makes use of hexadecimal character(s), it requires changes (e.g. in signalling systems, switches and support systems). Although the solution does not require any resources from the national numbering plan, it does take up numbering resources (it uses a spare value from the Signalling System No. 7). (e164s2) 9.2 Separated addresses (e164s2) 9.2.1 Description In this address type, the routing number and the directory number are carried in two different fields in the signalling messages (Figure 10). The address identifying the destination of the ported call, routing number, is used to route the call. The DN is carried transparently in a separate signalling parameter and is only used at the called side to complete the call. +-----------------------+ | RN | +-----------------------+ +-----------------------+ | DN | +-----------------------+ Figure 10 - Showing a separated address (e164s2) 9.2.2 Brief analysis Pros: The routing number can either be an E.164 number or a non- E.164 number. In either case the routing number should be in the same format as the national numbering plan. Since the called number and routing number are carried in separate signalling parameters, the possibility for mis-routing is minimized. If non-E.164 numbers are used, all numbers from the national numbering plan can be used as routing numbers. If E.164 numbers are used, numbers within the national numbering plans must be identified and assigned only for routing purposes. As opposed to prefix solutions, no special treatment of routing numbers need to be provided by the routing mechanisms of the exchange. Gallant Expires January 6, 2001 21 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Cons: Such a separated address solution requires, by definition, that signalling systems used are able to carry both RN and DN in separate signalling parameters. (e164s2) 9.3 RN only (e164s2) 9.3.1 Description In this case the routing number is the only information being sent between exchanges/networks (Figure 11). The directory number, E.164 number, is not sent between exchanges but is translated into a routing number. The routing number must point out the access line to which the called party is connected as no other method is available. +-----------------------+ | RN | +-----------------------+ Figure 11 - Showing a routing number only (e164s2) 9.3.2 Brief analysis Pros: The advantages of this addressing method are that it is internationally available today because the RNs are E.164 numbers and that it does not require any changes in the signalling systems. Cons: To be able to provide information regarding the DN, in services like COLP, a second query in the recipient exchange (or in the last transit exchange) is needed. This solution can waste numbering resources (depending on the solution). (e164s2) 9.4 Only DN (normally across network boundaries) (e164s2) 9.4.1 Description In this case the directory number is the only information that is being sent between networks. +-----------------------+ | DN | +-----------------------+ Figure 12 - Showing a directory number only Gallant Expires January 6, 2001 22 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 (e164s2) 9.4.2 Brief analysis Pros: It is not mandatory to introduce RN transfer between networks, i.e. this solution does not affect existing network interfaces. It allows different addressing options of different operators to work together. Operators will have to transport routing information with ported calls inside their networks, regardless of which number portability solution is chosen. There are multiple options to transport this routing information. Separation or concatenation of routing information and directory number is the main characteristic. Internal routing is not dependent on information given by other networks (no network interdependence). Cons: Use of this addressing method requires the use of "all call query all networks" architecture at the network interface. (e164s2) 10 Combinations of addressing types, addressed entities and mechanisms: general signalling requirements The previous clauses above have identified that there are three components that must be determined in any implementation of service provider number portability: 1) the entity addressed by the routing number; 2) the method of transporting the routing number; 3) the architecture used to determine the routing number. Addressed entity: Assuming a routing number is utilized (see below), there are four possible entities that can be identified by the routing number: 1) network termination point; 2) recipient exchange; 3) recipient network; 4) point of interconnection. Transport of routing number: There are four transport methods described: 1) concatenated; 2) separated; 3) no routing number used; 4) routing number only. Gallant Expires January 6, 2001 23 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Architectures: There are four architectures described: 1) onward routing; 2) dropback; 3) query on release; 4) all call query. With the exception of the "No routing number used/routing number only" transport mechanisms, the three components are independent of one another, allowing a multitude of theoretically possible solutions by combining the components. For example, an implementation could consist of: - Routing number identifies the recipient exchange, is transported concatenated with dialled digits and is derived using an onward routing architecture. Or, an alternate implementation could be: - Routing number identifies the recipient network, is transported in a separate field to the dialled digits and is derived using an all call query architecture. The various combinations provide flexibility of implementation to take into account economical and technical parameters of each individual situation. For this reason this Supplement does not recommend one solution over another. (e164s2) 11 Examples of locations of number portability database(s) within networks (e164s2) 11.1 General description Depending on the evolutionary level in a particular network, the NP database will be located in different places of the network or possibly even external to the network. The following principles of NP data storing have been identified, described and evaluated: a) exchange-based (distributed) solutions; b) exchange external (centralized) solutions. The following options for NP data query places have been identified, described and evaluated: 1) originating local exchange; 2) gateway exchange(s); 3) transit or gateway exchange(s); 4) donor local exchange(s). Gallant Expires January 6, 2001 24 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 Regardless of data storing place, the exchange/network can act according to different NP principles, e.g. onward routing the call, dropping back the rerouting information or even acting as a database and responding a query with rerouting information. (e164s2) 12 Administrative processes In establishing number portability, processes that underpin its introduction and management are a key requirement. The following list provides top level guidance on specific areas of activity and the steps that need to be covered. Process activity Steps to be covered Service Initial contact between operators establishment Planning stage Implementation planning Network implementation and testing Service Introduction of a new switch maintenance Introduction of a new numbering block Number change New routing number Service Request ordering Validation Scheduling Contingency plans Hours Subsequent portability Change of account name Reasons for rejection Installation Cancellation Fault and repair handling Directory number Directory entries information Operator assistance Emergency service Number plan administration Law enforcement agencies Billing -------------------------------------------------------------------- Gallant Expires January 6, 2001 25 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 5. Front Matter from the ITU-T Published Version This section contains sections from the front matter of the ITU-T published version of Supplement 2 to Rec. E.164, including the Source, the Foreword, the note on "ROA," the text on intellectual property rights, and the copyright notice. They are provided here for information and reference. The text here was valid at the time of publication, but there may have been revisions since then. 5.1 Source (from the ITU-T published version) Supplement 2 to ITU-T Recommendation E.164 was prepared by ITU-T Study Group 2 (1997-2000) and was approved under the WTSC Resolution No. 5 procedure on the 9th of November 1998. 5.2 FOREWORD (from the ITU-T published version) ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. 5.3 NOTE (from the ITU-T published version) In this Recommendation the term "recognized operating agency" (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms "Administration," "ROA" and "public correspondence" are defined in the "Constitution of the ITU (Geneva, 1992). Gallant Expires January 6, 2001 26 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 5.4 INTELLECTUAL PROPERTY RIGHTS (from the ITU-T published version) The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. 5.5 Copyright Notice (from E.164 Supp. 2, ITU-T published version) (c) ITU 1999 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. 6. Security Considerations None. 7. References 1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. 2 ITU-T Recommendation E.164 (05/97), "The international public telecommunication numbering plan". 3 Supplement 2 (11/98) to ITU-T Recommendation E.164 (05/97), "Supplement 2: Number Portability". 4 "Report of the IP-Telecoms Interworking Workshop (Numbering, Naming, Addressing and Routing), ITU, Geneva 25-27 January 2000", http://www.itu.int/ITU-T/ip-telecoms/ip-telecoms.htm, last modified 2000-03-20. 5 "Telephone Number Mapping (enum)", last modified 03-Jul-00, http://www.ietf.org/html.charters/enum-charter.html. Gallant Expires January 6, 2001 27 Internet-Draft Number Portability (E.164 Supp. 2) July 7, 2000 8. Acknowledgments I would like to thank the ITU TSB (Telecommunication Standardization Bureau), and Mr. John Tar in particular, for helping to make the text of Supplement 2 to E.164 freely available on the ITU web site. 9. Author's Address Andrew Gallant Comsat Corporation 6560 Rock Spring Drive Bethesda, MD 20817 USA Phone: +1 301 214 3264 Fax: +1 301 214 7226 Email: andrew.gallant@comsat.com Full Copyright Statement Copyright (C) The Internet Society (2000). 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 implmentation 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. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Gallant Expires January 6, 2001 28