S. Lind Internet Draft AT&T Document: draft-lind-itut-e370-00.txt July 2000 Category: Informational Service Principles when Public Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks Status of this Memo This document is an Internet-Draft and is NOT offered in accordance with Section 10 of RFC2026, and the author does not provide the IETF with any rights other than to publish as an Internet-Draft 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 describes the current thinking of the collaborators of ITU-T Question 10/2, "Management and development of PSTN-based telecommunication services," about service principles when public circuit switched international telecommunication networks interwork with IP-based networks. This document contains most of the text (there has been some rearrangement of the text) from draft new Recommendation E.370 [1], starting from section 3 of this Internet Draft, which was determined to be stable at the March 2000 meeting of Study Group 2. It may be approved by the members of the ITU, subject to written comments received from those members, at a meeting of the Study Group (or its successor) in early 2001 (provisionally 23-26 January 2001). It is hoped that this document will further the collaborative efforts between Study Group 2 and the various working groups of the IETF. 2. Conventions used in this document Lind Informational - Expires January 2001 1 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [2]. 3. Introduction There is an increased availability of Internet Protocol (IP)-based networks on an international and national basis. Users of these IP- based networks expect to be able to be connected with users of public, circuit switched, international telecommunications networks. In order to ensure that the needs of both IP-based network users and circuit-switched, international telecommunication network users are met, principles of interworking between IP-based networks and the circuit-switched, international telecommunication networks are presented in this Recommendation. 4. Scope This Recommendation defines the principles applicable to international public correspondence services provided by IP-based networks interworking with the ITU-defined, circuit-switched, public, international telecommunication networks (for example, the PSTN, ISDN, and PLMN). This Recommendation is applicable to those cases where the IP-based network is implemented by a separate service provider (e.g., ROA) from the service provider of the public, circuit-switched international telecommunication network. It does not cover the case where IP technology is integrated within the international telecommunication network of a single service provider. 5. Definitions IP-based network: A network in which the Internet Protocol is used as the ISO layer 3 protocol (OSI Reference Model). 6. Abbreviations For the purpose of this Recommendation, the following abbreviations are used: DTMF Dual Tone Multi-Frequency IP Internet Protocol ISDN Integrated Services Digital Network ISO International Standards Organization ITU International Telecommunication Union ITU-T International Telecommunication Union - Telecommunication Standardisation Sector Lind Informational - Expires January 2001 2 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks IWF Interworking Facility OSI Open System Interconnection PLMN Public Land Mobile Network PSTN Public Switched Telephone Network ROA Recognised Operating Agency SIP Session Initiation Protocol 7. General Principles of Interconnection In general, the interconnection of a IP-based network to an existing international telecommunication network should not impose any requirement for additional functionality in the international telecommunication network, nor any restriction in the normal operation of the international telecommunication network. Any added functionality should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks. The international telecommunication network should not have to be specially engineered to compensate for possible performance variation of services supported by the IP-based network interconnected to it in order to match the performance of similar services fully supported by the international telecommunication network. The interconnection arrangements could be formalised by an agreement between the operators of the two networks. The agreement could cover the following areas: - network topology; - interface specifications, including signalling systems; - provisioning procedures; - operations and maintenance procedures; - performance monitoring (quality of service, grade of service, traffic measurement, etc.); - growth management (forecasts, network planning, etc.); - charging and accounting arrangements. It should be possible to setup calls: a) that originate at a terminal (such as those based on H.323 [3] or SIP [4]) on an IP-based network and terminate at terminals on PSTN/ISDN/PLMN networks; b) that originate at terminals on PSTN/ISDN/PLMN networks and terminate at a terminal on an IP-based network. Backward and forward call clearing should be possible. The detection of a non-recoverable failure of any of the critical resources involved in the call shall initiate the clearing of the call. Lind Informational - Expires January 2001 3 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks User services, which make use of end to end bi-directional and unidirectional DTMF signaling, should be supported e.g. voice mail applications, conference bridge applications, etc. An inability to complete the call within the PSTN/ISDN/PLMN network should be detected and communicated to the calling party (e.g. busy tone). The ability for inband audio tones and announcements to be received by the caller should be supported (e.g. special information tones, referral messages, etc). In order to preserve existing PSTN/ISDN/PLMN service features the following should be supported: a) Presentation of a number in ITU-T Recommendation E.164 [5] format identifying the Calling Party for Calling Line Identification Presentation; b) Transport of calling line identification; c) Transport of calling line identification restriction; d) Malicious call tracing; e) Emergency calling; f) International Emergency Preference Scheme (see Recommendation E.106 [6]) g) E.164 number portability. 8. Services The services, including any supplementary services, offered by IP- based networks (voice, data, etc) when interworking with the international telecommunication networks to provide public correspondence services should, as far as practicable, be similar to those provided on those international telecommunication networks and work on an end-to-end basis. For example, when interworking with users on the PSTN, Recommendation E.105 [7] defines the requirements of the International Telephone Service. While it is recognized that the manner in which the services, including any supplementary services, are presented to users on an IP-based network may be different from the way in which those services are presented to users of the PSTN, ISDN and PLMN; the basic functions, as defined in the appropriate ITU-T Recommendation, should still operate across the various networks. Lind Informational - Expires January 2001 4 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks 9. Service Scenarios A number of scenarios may be deployed to reflect particular configurations of networks, namely: Scenario 1: communication between IP-based network users and International Telecommunication Network users, in which the call set-up is originated by the IP network user. Scenario 2: communication between IP-based network users and International Telecommunication Network users, in which the call set-up is originated by the International Telecommunication Network user. Scenario 3: communication between International Telecommunication Network users, using IP-based networks for the connection/trunking between the involved users. Scenario 4: communication between IP-based network users, using International Telecommunication Networks for the connection/trunking between the involved users. In principle the interworking between the IP-based network and the international telecommunication network can be at any level in the international telecommunication network hierarchy, e.g. local exchange, transit exchange, international exchange For all scenarios, any added functionality to enable interworking should be provided in the IP-based network, unless otherwise agreed between the operators of the IP-based and international telecommunication networks. In the case of scenarios 3 and 4, the IP-based network is provided by a separate entity (e.g., ROA) from the international telecommunication network. Recommendation E.370 does not cover the case where IP technology is integrated within the international telecommunication network of a single service provider. The traffic, technical, economical, and administrative advantages/disadvantages should be considered before such interconnection is proposed by network operators. 10. Operation When interworking between IP-based networks and international telecommunication networks the operational procedures for services should, wherever possible, be the same as for those on the international telecommunications networks. The same tones, announcements, service codes and signals, etc., used in the international telecommunication services should be recognised and where appropriate returned by the IP-based network. For interworking Lind Informational - Expires January 2001 5 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks between IP-based networks and international telecommunication networks, User-to-Network signalling (where a user on one network is accessing functionality supplied on the other network), Network-to- Network signalling, and User-to-User signalling must be consistently interpreted across the various networks. The latter case is particularly important when users must interact with interactive voice response systems. For users on the international telecommunication networks to reach users on IP-based networks, terminals on the IP-based network should be addressable using the international numbering plan applicable to the International telecommunications services (i.e., Recommendation E.164). There should be mechanisms in place to cater for the needs of any call recording, billing and international accounting functions that might be required. For example, an answer supervisory signal should be returned by the terminating network when an incoming call is established. 11. Quality of Service When international telecommunication networks interwork with IP- based networks, the quality of service experienced by the users should, as far as practible, be the same as if there had been no interworking involved. Note: Categories of speech quality are defined in Recommendation G.109 [8]. 12. References 1 ITU-T Draft New Recommendation E.370, Service principles when public circuit switched international telecommunication networks interwork with IP-based networks, COM 2-R077, March 2000 2 Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 3 ITU-T Recommendation H.323, Packet-based multimedia communications systems, September 1999 4 M. Handley, H. Schulzrinne, E. Schooler, and J. Rosenberg, "SIP: session initiation protocol," RFC 2543, March 1999 5 ITU-T Recommendation E.164, The international public telecommunication numbering plan, May 1997 6 ITU-T Recommendation E.106, International Emergency Preference Scheme, March 2000 Lind Informational - Expires January 2001 6 Service Principles when Public July 2001 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks 7 ITU-T Recommendation E.105, International Telephone Service, August 1992 8 ITU-T Recommendation G.109 - Definition of categories of speech transmission quality, September 1999 13. Author's Address Steven D. Lind AT&T 180 Park Avenue, Bldg. 2, Room 2G25 Florham Park, NJ 07932 Phone: +1 973 236 6787 Email: sdlind@att.com Lind Informational - Expires January 2001 7 Service Principles when Public June 2000 Circuit-Switched International Telecommunication Networks Interwork with IP-based Networks 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 implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. 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. Lind Informational - Expires December 2000 8