Roaming—an overview

Roaming allows you to use the same credentials in various localities to gain Internet access. There are two very common usages of roaming today. Let's see how they work.

Agreement between an ISP and a Telco

Consider the following diagram:

• Alice is a client of my-isp.com. My-isp.com does not have its own infrastructure.
• my-isp.com, however, has an agreement with the local Telco. The Telco allows clients from my-isp.com to connect to the Internet using the Telco's DSL Concentrator equipment.
• The local Telco's DSL Concentrator will first forward authentication requests to the Telco RADIUS Server.
• Because of the realm (@my-isp.com) these requests will be proxied to the my-isp.com RADIUS Server.
• The local Telco RADIUS Server in effect becomes just another client to the my-isp.com RADIUS Server.

Some of the advantages of this are:

• my-isp.com does not require its own infrastructure.
• my-isp.com can have multiple independent agreements with other infrastructure providers...