ROAMOPS Working Group Bernard Aboba
INTERNET-DRAFT Microsoft
Category: Standards Track
<draft-ietf-roamops-nai-04.txt>
7 June 1997
The Network Access Identifier
1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working docu-
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The distribution of this memo is unlimited. It is filed as <draft-
ietf-roamops-nai-04.txt> and expires January 1, 1998. Please send
comments to the authors.
2. Abstract
In order to enhance the interoperability of roaming and tunneling ser-
vices, it is desirable to have a standardized method for identifying
users. This document proposes syntax for the Network Access Identi-
fier (NAI). It is expected that this will be of interest for support
of roaming as well as tunneling. "Roaming capability" may be loosely
defined as the ability to use any one of multiple Internet service
providers (ISPs), while maintaining a formal, customer-vendor rela-
tionship with only one. Examples of cases where roaming capability
might be required include ISP "confederations" and ISP-provided corpo-
rate 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
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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
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.
In order to enhance the interoperability of roaming and tunneling ser-
vices, it is desirable to have a standardized method for identifying
users. This document proposes syntax for the Network Access Identi-
fier (NAI). Methods for authentication routing or determination of
tunnel server endpoints will be addressed in future documents.
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 PPP authentication. In roaming, the
purpose of the NAI is to identify the user as well as to
assist in the routing of the authentication request. 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.
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).
3.2. Purpose
As described in [1], there are now at least five services implementing
dialup roaming, and the number of Internet Service Providers involved
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 Network
Access Identifier (NAI) submitted by the user to the NAS in the ini-
tial PPP authentication. It is also expected that PACs and LACs will
use the NAI as part of the process of opening a new tunnel, in order
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to determine the tunnel endpoint.
As proposed in this document, the Network Access Identifer is of the
form user@realm. Please note that while the realm is typically a Fully
Qualified Domain Name (FQDN) it is not required that this be the case,
and use of an FQDN as the realm does not imply use of DNS for location
of the RADIUS server or authentication routing.
Since to date roaming has been implemented on a relatively small
scale, existing implementations handle location of RADIUS servers
within a domain and perform authentication routing based on local
knowledge expressed in proxy configuration files. To date implementa-
tions have not found a need for use of DNS for location of the RADIUS
server within a domain, although this can be accomplished via use of
the DNS SRV record. Similarly, existing implementions have not found
a need for dynamic routing protocols, or propagation of global routing
information.
4. Formal Definition of the NAI
The grammar for the NAI is given below, using the augmented BNF nota-
tion described in reference [4].
NAI = USERNAME ["@" REALM]
REALM = token "." token *[ "." token ]
USERNAME = token
Examples of valid Network Access Identifiers include:
fred
fred@bigco.com
nancy@eng.bigu.edu
Examples of invalid Network Access Identifiers include:
howard.edu
fred@bigco.com@smallco.com
bigco!fred@smallco.com
bigco%fred@smallco.com
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, W. Wang. "Review of Roaming
Implementations." Work in progress, draft-ietf-roamops-imprev-02.txt,
Microsoft, Aimnet, i-Pass Alliance, Asiainfo, Merit, May, 1997.
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[2] C. Rigney, A. Rubens, W. Simpson, S. Willens. "Remote Authenti-
cation Dial In User Service (RADIUS)." RFC 2058, Livingston, Merit,
Daydreamer, January, 1997.
[3] C. Rigney. "RADIUS Accounting." RFC 2059, Livingston, January,
1997.
[4] R. Fielding, et al. "Hypertext Transfer Protocol - HTTP/1.1."
draft-ietf-http-v11-spec-07, UC Irvine, August, 1996.
7. Authors' Addresses
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
Phone: 206-936-6605
EMail: bernarda@microsoft.com
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