Internet Draft Title: draft-lee-e164-framework-00.txt C. C. Lee Date: November, 1998 M. Orsic Lucent Technologies A Framework for E.164 Number to IP Address Mapping Status of this Memo This document is 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 work- ing 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 mate- rial or to cite them other than as "work in progress." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.ietf.org (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Abstract This internet draft describes a framework for mapping the E.164 number of internet telephony (IT) subscribers to an IP addresses so that calls can be delivered to IT subscribers. The draft describes: - assumptions that the framework is based on - goals that the framework is designed for - functionality of network entities Several scenarios are included to illustrate the procedure. 1.0 Introduction Lee et al. expired May 1999 [Page 1] Internet Draft E.164 to IP Mapping November1 1998 This internet draft describes a framework for mapping an E.164 number [E.164] of an internet telephony (IT) subscriber to an IP address so that calls can be delivered to the subscriber. Assigning E.164 numbers to IT subscribers not only makes it easier for traditional phone users to call IT subscribers, but it will also allow service providers to leverage the existing infrastructure to provide IT services. It can also facilitate the convergence of wireline/wireless services and emerging IT enhanced services. The assignment of E.164 numbers to IT subscribers and the IP address based routing in the internet give rise to a fundamental need for mapping the E.164 numbers to IP addresses in the IT infrastructure. The IT subscribers may gain access to the IP network by employing wired-line, wireless (e.g. wireless LAN, cellular access), or cable- modem connections. Roaming IT subscribers should be able to log onto the IP network from any location, while the IT subscribers that use fixed access will be connected to the IP network at fixed location. Calls to IT subscribers may originate from PSTN wireline, wireless subscribers, or from other IT subscribers. It is assumed in this draft that when placing a call to an IT subscriber, the caller will specify the E.164 as a called number. The problem of IT gateway discovery for IP originated and PSTN terminated calls based on the called subscriber's E.164 PSTN number is currently being addressed by the IPTEL working group [GLP] and is outside the scope of this draft. The requirements needed to design a new protocol or to enhance an existing protocol will have to be addressed after the mapping framework has been determined. No attempts have been made to map the functionality of servers involved in this framework to existing servers in the internet or PSTN servers that are IP enabled. It will be advantageous to enhance existing servers to realize this framework. Candidates may include IP enabled Service Control Points, IP enabled HLR/VLR, DNS, LDAP servers, Radius servers, and other existing internet directory servers. 1.1 Terminal Status When a call to an IT terminal is initiated, the called IT terminal may be in one of three different states. Each state has a certain level of readiness depending on the IP network to which the IT terminal is connected. Lee et al. expired May 1999 [Page 2] Internet Draft E.164 to IP Mapping November1 1998 - When in a "idle" state, no calls can be delivered to the IT terminal. The terminal may be powered off or it is powered on but not connected to the IP network. At this state, no dynamic IP address is assigned to the terminal and no IT calls can be delivered to it. - In a "standby" state, the IT terminal is powered on, connected to the IP network and has an IP address assigned, but the IT application is not running. In this state, no calls can be delivered to the IT terminal. There are several ways a transition from the "idle" state to the "standby" state can occur. Users may connect to the network by registration during which IP addresses are assigned to the terminals. For wireless accessed terminals, the paging mechanism may be used to trigger the transition. When the mobile is paged with an indication of data serivce type, it may initiate a registration process to get the terminal connected to the IP network and obtain an IP address. - In the "ready" state, the IT terminal is connected to the IP network, has an IP address assigned, and the IT application has been invoked. The terminal is ready to receive an incoming IT call. The transition from the "standby" state to the "ready" state may be triggered manually by users or automatically by programs in the terminals. 2.0 Acronym DDS: Dynamic Directory Server DNS: Domain Name Server HLR: Home Location Register IMSI: International Mobile Subscriber Identity ISP: Internet Service Provider IT: Internet Telephony ITHS: Internet Telephony Home Server LDAP: Lightweight Directory Access Protocol MSC: Mobile Switching Center NAI: Network Access Identifier NAS: Network Access Server RAS: Registration Authentication and Status SCP: Service Control Point Lee et al. expired May 1999 [Page 3] Internet Draft E.164 to IP Mapping November1 1998 SIP: Session Initiation Protocol VLR: Visitor Location Register 3.0 Framework Design Basis The framework documented in this internet draft is designed based on the following assumptions: - E.164 numbers are managed by existing numbering management administrations. Internationally, the ITU Telecommunication Standard Board assigns country/service codes; and within a geographic area, a national or regional numbering administration has the responsibility of managing the numbering plan for the countries assigned to the area. To have the E.164 number allocation process managed by the existing numbering plan administrations can expedite the allocation process, leading to an earlier IT service deployment. Internet telephony service providers will obtain blocks of E.164 numbers from numbering plan administrations for their subscribers. - For scalability purpose, subscriber-related data may be partitioned and distributed among multiple servers of the same type. These servers may be owned by individual service providers or by trusted third party service providers. - An IT subscriber with a specific E.164 number will ordinarily subscribe to the service of one IT service provider. The service provider or a trusted third provider will maintain the data related to that subscriber, including the IP address that the subscriber can currently be reached. If the subscriber uses the same E.164 number for the same service from more than one provider, other criteria need to be used for determining which service provider's subscriber database to be consulted for call delivery. It is emphasized that the service provider whose database was queried needs not carry the call. 4.0 Design Goals The design goals of the framework are described as follows: Lee et al. expired May 1999 [Page 4] Internet Draft E.164 to IP Mapping November1 1998 - Because some, and gradually more, of internet service subscribers will be assigned IP addresses dynamically even if they access the network from fixed locations, the framework needs to support the mapping to a dynamically assigned IP address. For subscribers with static IP addresses assigned, a subset of the framework may be used for the mapping. - The framework should allow the call originator to use an internet telephony service provider that is different from the one subscribed to by the call recipient. - The framework should allow for enhanced services to be provided in conjunction with the framework. For example, to provide a "least cost" service, a "bidding" server may be consulted before the mapping to find the least cost service provider for carrying the call. - The framework should allow for including more information into the query than just the phone number or prefix and the security information; and more output in the response than just the IP address for contact. The response may contain such information as the call receiving status of the destination equipment, call restrictions, or information to be placed into subsequent SIP or H.323 message (e.g. authorization information). - The framework should allow for information to be exchanged for subsequent collection of fees incurred. - The framework should allow for scalability to support high capacity. - The framework should allow for PSTN/IT convergence, including wired access and wireless access for subscribers. - The framework should support service mobility for roaming IT subscribers. When a roaming IT subscriber accesses the internet from a location different than the home location, the same services offered on the home network should be available to the roaming IT subscriber on the visited network. - The framework should allow service providers, who prefer to maintain otherwise separate network infrastructures for different services, to deploy a common infrastructure for similar types of mapping. In this case, the type of mapping requested will qualify the request. Lee et al. expired May 1999 [Page 5] Internet Draft E.164 to IP Mapping November1 1998 5.0 Architecture Framework Figure 1 shows the proposed E.164 number to IP address mapping framework. This arrangement is modeled after the location management and call delivery aspect of the wireless network architecture. The wireless network has addressed and solved the problem of delivering a call to a mobile subscriber whose point of attachment (i.e. dynamic address) to the network changes from time to time. Lee et al. expired May 1999 [Page 6] Internet Draft E.164 to IP Mapping November1 1998 . Internet . PSTN . ______ . | | . | IT | . _____ |Subscr|. . |Wired| |______| . ____._____ |Phone| call . | | . |_____| recipient . | IT | . call .____ ____ | Gateway |. originator | | | | | or | |DDS |..|ITHS|..| | |____| |____| | IT | . | Call |. ______ . |Processing| . _________ | | . .| Proxy | . | | | IT |. . |__________| |WLS Phone| |Subscr| . . |_________| |______| . . call call ________ . originator recipient | | . |IT Subsc| . |________| . call originator . . . Internet . PSTN . Figure 1: Architecture Framework for E.164 Number to IP Address Mapping The major function of the Internet Telephony Home Server (ITHS) is to store static data for individual IT subscribers. The proposed Dynamic Directory Server (DDS) stores subscribers' dynamic data. The IT Gateway or the IT Call Processing Proxy is the requester for address mapping. The main function of the ITHS working in conjunction with DDS will be to find the IP address of the terminating IT subscriber or its proxy where terminating call request shall be sent. Lee et al. expired May 1999 [Page 7] Internet Draft E.164 to IP Mapping November1 1998 There will be multiple ITHSs and DDSs in the network infrastructure. The ITHS and the DDS can be geographically distributed and the DDS may be located at the point of registration. Note that if no mobility is involved and capacity is not an issue, the ITHS and the DDS may be collocated or reside on the same hardware. 5.1 Functionality of Internet Telephony Home Register When a call is to be delivered to an IT subscriber, the ITHS of the called IT subscriber is consulted for the call delivery. The IT subscriber's static data stored in the ITHS may include: - subscriber identifier information, E.164 number, network access identifier (NAI) [NAI], etc - billing related information, e.g. tokens - security related information, and - the IP address or a pointer to the DDS where the IT subscriber is currently registered 5.2 Functionality of Dynamic Directory Server The major function of the DDS is to store the dynamic data for individual IT subscribers. The IT subscriber's data stored in the DDS may include: - subscriber identifier information, including network access identifier, - for wireless subscribers, paging information used by the paging system to request that the IT terminal registers with a local IP network, - subscribers IP address stored at the registration time - current status for receiving IT calls - capability of equipment a subscriber uses currently, Lee et al. expired May 1999 [Page 8] Internet Draft E.164 to IP Mapping November1 1998 - other call delivery related information, such as session key and other security related information, and - pointers to ITHS. 5.3 Basic Scenario 5.3.1 Subscriber Registration The registration procedure may be initiated by the IT terminal or it may be requested by the network, upon incoming call arrival, by employing the paging mechanism. - A message to request for registration is received from the terminal. The subscriber is authenticated, and a temporary IP address is assigned to the terminal. The network access server will inform the DDS of the IP address if the subscriber has subscribed to IT services. - The DDS stores the IP address to user identifier association in its database. - The DDS sends a message to inform the ITHS of the identifier of the DDS where the subscriber is currently registered. The address of the ITHS is obtined based on the NAI of the subscriber. For fixed accessed subscribers, this and the next steps need not be performed for every registration. - The ITHS stores the NAI to DDS identifier association in its database. 5.3.2 PSTN to IT Subscriber Call Delivery The scenario described below illustrates a call to a IT subscriber that originated from a PSTN subscriber. Lee et al. expired May 1999 [Page 9] Internet Draft E.164 to IP Mapping November1 1998 - The IT gateway receives a call from the PSTN. The IT Gateway, finds the location of the ITHS for the respective IT subscriber by consulting a translation table, internally or externally. - The IT Gateway sends the E.164-to-IP-address mapping request to the ITHS and specifies the type of information desired. - The ITHS receives the request that indicates an IT terminating call and informs the DDS of the incoming call and requests IP address information. - Based on the IT terminal status, the DDS either pages the IT terminal triggering the registration procedure or the requested information is already available. Upon completion of the registration procedure, the DDS retrieves the IP address and other information requested from its data store, forms a response, and sends it back to the ITHS. - The ITHS retrieves other information requested by the IT Gateway, sends a response to the IT Gateway together with the IP address. Now the gateway can start call setup procedures to the destination subscriber as per H.323 version 2 [H323], Session Initiation Protocol [SIP], or other protocols. 6.0 Security Considerations Security is vital for the framework to be implemented in the internet environment. This may include - mutual authentication of the query source and the response source for each transaction, - non-repudiation of response. This is most important when cost related information is exchanged in the messages. The non- repudiation for query may also be needed depending on business arrangement among service providers, - query authorization, - response data integrity, and - message confidentiality if data carried includes security sensitive information, such as a session key Lee et al. expired May 1999 [Page 10] Internet Draft E.164 to IP Mapping November1 1998 The security requirements should be communicated to the Authentication Authorization and Accounting Working Group. 7.0 Reference - [E.164] ITU-T, E.164, "The International Public Telecommunication Numbering Plan", 5/1997 - [NAI] Aboba, Beadles, "Network Access Identifier", Internet- Draft, draft-ietf-roamops-nai-11.txt, July 1998 - [H323] ITU-T, H.323, "Packet-based multimedia communications systems", 2/1998 - [SIP] Handley, Schulzrinne, Schooler, Rosenberg, "SIP: Session Initiation Protocol", Internet-Draft, draft-ietf-mmusic-sip- 09.txt, 9/1998 - [GLP] Rosenberg, Schulzrinne, A Framework for a Gateway Location Protocol", draft-ietf-iptel-gwloc-framework-01.txt , 10/1998 - Faltstrom, "Where to terminate a phone call", Internet Draft, draft-faltstrom-e164-00.txt Author's Address Milo Orsic Lucent Technologies 263 Shuman Blvd Naperville, IL 60566 Phone: (630) 713 5161 Email: orsic@lucent.com Chinmei Lee Lucent Technologies 263 Shuman Blvd Naperville, IL 60566 Phone: (630) 713 7256 Lee et al. expired May 1999 [Page 11] Internet Draft E.164 to IP Mapping November1 1998 EMail: chinmeilee@lucent.com Lee et al. expired May 1999 [Page 12]