Review of Roaming Implementations
RFC 2194

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Network Working Group                                         B. Aboba
Request for Comments: 2194                                   Microsoft
Category: Informational                                          J. Lu
                                                        AimQuest Corp.
                                                              J. Alsop
                                                       i-Pass Alliance
                                                               J. Ding
                                                              Asiainfo
                                                               W. Wang
                                                   Merit Network, Inc.
                                                        September 1997

                   Review of Roaming Implementations

1.  Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

2.  Abstract

   This document reviews the design and functionality of existing
   roaming implementations.  "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 relationship with
   only one.  Examples of cases where roaming capability might be
   required include ISP "confederations" 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 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 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
      service in a group of countries or on a continent.

      Businesses desiring to offer their employees a comprehensive
      package of access services on a global basis.  Those services may

Aboba, et. al.               Informational                      [Page 1]
RFC 2194           Review of Roaming Implementations      September 1997

      include Internet access as well as secure access to corporate
      intranets via a Virtual Private Network (VPN), enabled by
      tunneling protocols such as PPTP, L2F, or L2TP.

   What is required to provide roaming capability?  The following list
   is a first cut at defining the requirements for successful roaming
   among an arbitrary set of ISPs:

      Phone number presentation
      Phone number exchange
      Phone book compilation
      Phone book update
      Connection management
      Authentication
      NAS Configuration/Authorization
      Address assignment and routing
      Security
      Accounting

   In this document we review existing roaming implementations,
   describing their functionality within this framework.  In addition to
   full fledged roaming implementations, we will also review
   implementations that, while not meeting the strict definition of
   roaming, address several of these problem elements. These
   implementations typically fall into the category of shared use
   networks or non-IP dialup networks.

3.1.  Terminology

   This document frequently uses the following terms:

   home ISP  This is the Internet service provider with whom the user
          maintains an account relationship.

   local ISP This is the Internet service provider whom the user calls
          in order to get access. Where roaming is implemented the local
          ISP may be different from the home ISP.

   phone book
          This is a database or document containing data pertaining to
          dialup access, including phone numbers and any associated
          attributes.

Aboba, et. al.               Informational                      [Page 2]
RFC 2194           Review of Roaming Implementations      September 1997

   shared use network
          This is an IP dialup network whose use is shared by two or
          more organizations.  Shared use networks typically implement
          distributed authentication and accounting in order to
          facilitate the relationship among the sharing parties. Since
          these facilities are also required for implementation of
          roaming, implementation of shared use is frequently a first
          step toward development of roaming capabilities.  In fact, one
          of the ways by which a provider may offer roaming service is
          to conclude shared use agreements with multiple networks.
          However, to date the ability to accomplish this has been
          hampered by lack of interoperability among shared use
          implementations.