Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

Roaming has several meanings in the telecommunications and networking environment. The cellular phone industry refers to roaming as the ability of a subscriber to move among different service providers. Roaming also applies to wireless LANs. A company that installs wireless LANs throughout its offices may need to set up radio hubs at various points throughout the building. Roaming allows a user with a mobile device to move out of the range of one hub and into the range of another while maintaining a connection with the network. See "Wireless LANs."

Roaming is supported in network operating systems like Microsoft Windows 2000 with its IntelliMirror feature. IntelliMirror is a set of management technologies that provide desktop change and configuration management. User's data, personal computer settings, and the computing environment follows them to other locations as they travel with portable computers. See "IntelliMirror" and "Mobile Computing."

Another form of wireless networking is much broader in scope. The IETF Roaming Operations (roamops) Working Group is developing procedures, mechanisms, and protocols to support users roaming among groups of ISPs. This is different from, but related to, the work of the IP Routing for Wireless/Mobile Hosts Working Group (mobileip) in that the roamops group is not concerned with the movement of hosts or subnets, but of users.

Internet roaming services are offered by confederations of ISPs within a particular region that want to offer better service to their customers. National ISPs in different countries may also offer roaming services. GRIC (Global Reach Internet Connection) is the best example, as discussed later.

Internet RFC 2477 (Criteria for Evaluating Roaming Protocols, January 1999) defines Internet roaming as "the ability to use multiple Internet service providers while maintaining a formal, customer-vendor relationship with only one." RFC 2194 (Review of Roaming Implementations, September 1997) also provides details. The roaming architecture consists of three major subsystems:

• Phone book subsystem    The phone book subsystem provides the user with phone numbers that can be dialed from different locations in order to connect into the roaming-enabled network.


• Authentication subsystem    This system forwards user authentication information to the user's home ISP for verification.


• Accounting subsystem    This system keeps track of the services provided to users so that service providers can be compensated for the services they provide.

RFC 2486 (The Network Access Identifier, January 1999) discusses methods for identifying a roaming user's home authentication server. This is accomplished via the NAI (network access identifier), which is the user identification submitted by a client to a network access server during PPP authentication. RFC 2607 (Proxy Chaining and Policy Implementation in Roaming, June 1999) describes proxy chaining, which is the method that a network access server uses to consult the user's home server and have that home server authenticate the roaming user via the NAI information.

In 1996, ten ISPs in various countries formed the GRIC (Global Reach Internet Connection) with the goal of implementing a global roaming service, and to coordinate billing and settlement among the members. Today, GRIC is composed of over 300 service providers that form one seamless global network called the GRIC Alliance Network.

GRIC offers a variety of roaming services, including a platform that enables service providers to deploy and manage multiple Internet services such as worldwide authentication, authorization, routing, settlement, and provisioning in a way that ensures service providers will be reimbursed for the services they provide. It also offers users logons throughout the world, as well as VPN and VoIP services. See the GRIC Web site listed shortly.

A somewhat related topic is OSP (Open Settlement Protocol), which is a client/server protocol that Internet service providers use to exchange authorization, accounting, and usage information to support IP telephony.

Copyright (c) 2001 Tom Sheldon and Big Sur Multimedia.
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