ROAMOPS Working Group Bernard Aboba INTERNET-DRAFT Microsoft Corporation The Network Access Identifier 1. Status of this Memo This document is an Internet-Draft. Internet-Drafts are working docu- ments 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 ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). The distribution of this memo is unlimited. It is filed as and expires September 15, 1997. Please send comments to the authors. 2. Abstract This document describes issues relating to user identification in pro- vision of "roaming capability" for dialup Internet users. "Roaming capability" may be loosely defined as the ability to use any one of multiple Internet service providers (ISPs), while maintaining a for- mal, customer-vendor relationship with only one. Examples of cases where roaming capability might be required include ISP "confedera- tions" and ISP-provided corporate network access support. 3. Introduction Considerable interest has arisen recently in a set of features that fit within the general category of "roaming capability" for dialup Internet users. Interested parties have included: Regional Internet Service Providers (ISPs) operating within a particular state or province, looking to combine their efforts with those of other regional providers to offer dialup service over a wider area. National ISPs wishing to combine their operations with those of one or more ISPs in another nation to offer more comprehensive Aboba [Page 1] INTERNET-DRAFT 6 March 1997 dialup service in a group of countries or on a continent. Businesses desiring to offer their employees a comprehensive package of dialup services on a global basis. Those services may include Internet access as well as secure access to corporate intranets via a Virtual Private Network (VPN), enabled by tunnel- ing protocols such as PPTP, L2F and L2TP. This document focuses on issues of user identification for use in roaming services. However, since roaming and tunneling are closely related, it is believed that the considerations described here will also be of interest to those working on tunneling. 3.1. Terminology This document frequently uses the following terms: Network Access Identifier The Network Access Identifier (NAI) is the userID submitted by the client during the PPP negotiation. In roaming, the purpose of the NAI is to identify the user as well as to assist in the routing of the authentication request. As such, the NAI may be presented either in the form of an authentication route, or a pointer to such a route. Please note that the NAI may not necessarily be the same as the user's e-mail address or the userID submitted in an applica- tion layer authentication (i.e. HTTP authentication). In order to avoid confusion on this point, a new term was coined. Network Access Server The Network Access Server (NAS) is the device that clients dial in order to get access to the network. In PPTP termi- nology this is referred to as the PPTP Access Concentrator (PAC), and in L2TP terminology, it is referred to as the L2TP Access Concentrator (LAC). RADIUS server This is a server which provides for authentication/autho- rization via the protocol described in [3], and for account- ing as described in [4]. RADIUS proxy In order to provide for the routing of RADIUS authentication and accounting requests, a RADIUS proxy may employed. To the NAS, the RADIUS proxy acts as a RADIUS server, and to the RADIUS server, the proxy acts as a RADIUS client. 3.2. Purpose As described in[1], there are now at least four services implementing dialup roaming, and the number of Internet Service Providers involved Aboba [Page 2] INTERNET-DRAFT 6 March 1997 in roaming consortia is increasing rapidly. In order to be able to offer roaming capability, one of the require- ments is to be able to identify the user's home authentication server. For use in roaming, this function is accomplished via the NAI submit- ted by the user to the NAS in the initial PPP authentication. This document proposes syntax and semantics for the NAI. It is expected that this will be of interest for support of roaming as well as tunneling. For example, references [5] and [6] refer to use of the NAI in determining the tunnel endpoint. However, these references do not provide guidelines for how RADIUS or tunnel routing is to be accomplished. In order to avoid the possibility of conflicting and non-interoperable implementations, references [7] and [8] describe how RADIUS and tunneling protocols may be integrated. This document pro- vides guidance in the use of the NAI that is relevant to both the roaming and tunneling communities. 4. Formal Definition of the NAI As proposed in this specification, the Network Access Identifer is of the form user@domain, where the domain is a fully qualified domain name (FQDN). The syntax for the NAI is independent of the method used to route the authentication. In order to support the determination of the existence of a roaming relationship path between the local ISP and the home domain, one of two methods may be used. If the number of domains to be served is small, then it is possible to provide roaming relationship information via the authentication proxy configuration file. If the number of domains to be served is large, then a more scalable mechanism is rec- ommended, such as use of the DNS Roaming Relationship (REL) resource record, as described in [10]. However, even if use of the DNS is enabled, an authentication proxy will typically consult its configura- tion file for information on roaming relationships, prior to retriev- ing information via DNS. 4.1. BNF for the NAI The grammar for the NAI is given below, using the augmented BNF nota- tion described in reference [9]. NAI = USERNAME "@" FQDN FQDN = token "." token *[ "." token ] USERNAME = token Examples of valid Network Access Identifiers include: fred@bigco.com nancy@howard.edu Examples of invalid Network Access Identifiers include: Aboba [Page 3] INTERNET-DRAFT 6 March 1997 bigco howard.edu 5. Acknowledgements Thanks to Glen Zorn of Microsoft for many useful discussions of this problem space. 6. References [1] B. Aboba, J. Lu, J. Alsop, J. Ding. "Review of Roaming Implemen- tations." draft-ietf-roamops-imprev-01.txt, Microsoft, Aimnet, i-Pass Alliance, Asiainfo, January, 1997. [2] B. Aboba, G. Zorn. "Dialup Roaming Requirements." draft-ietf- roamops-roamreq-03.txt, Microsoft, March, 1997. [3] C. Rigney, A. Rubens, W. Simpson, S. Willens. "Remote Authenti- cation Dial In User Service (RADIUS)." RFC 2058, Livingston, Merit, Daydreamer, January, 1997. [4] C. Rigney. "RADIUS Accounting." RFC 2059, Livingston, January, 1997. [5] K. Hamzeh, T. Kolar, M. Littlewood, G. S. Pall, J. Taarud, A. J. Valencia, W. Verthein. "Layer Two Tunneling Protocol -- L2TP." draft- ietf-pppext-l2tp-01.txt, Ascend Communications, December, 1996. [6] K. Hamzeh, G. S. Pall, J. Taarud, W. Verthein, W. A. Little. "Point-to-Point Tunneling Protocol -- PPTP." draft-ietf-pppext- pptp-00.txt, Ascend Communications, June, 1996. [7] G. Zorn. "RADIUS Attributes for Tunnel Protocol Support." draft- ietf-radius-tunnel-auth-00.txt, Microsoft Corporation, November, 1996. [8] B. Aboba. "Implementation of Mandatory Tunneling via RADIUS." draft-ietf-radius-tunnel-imp-00.txt, Microsoft Corporation, February, 1997. [9] R. Fielding, et al. "Hypertext Transfer Protocol - HTTP/1.1." draft-ietf-http-v11-spec-07, UC Irvine, August, 1996. [10] B. Aboba. "The Roaming Relationship (REL) Resource Record in the DNS." draft-ietf-roamops-dnsrr-02.txt, Microsoft Corporation, March, 1997. 7. Authors' Addresses Bernard Aboba Microsoft Corporation Aboba [Page 4] INTERNET-DRAFT 6 March 1997 One Microsoft Way Redmond, WA 98052 Phone: 206-936-6605 EMail: bernarda@microsoft.com Aboba [Page 5]