The RADIUS protocol enables network access servers (NAS devices) to forward authentication requests over the Internet. Typically, the NAS communicates with the subscriber’s PC or laptop computer using the Point-to-Point Protocol (PPP). The NAS accepts PPP authentication requests from the subscriber, reformats them into RADIUS packets, and then forwards them to servers that support the RADIUS protocol, such as Internet Authentication Services. A unique password between the IAS and the NAS called a shared secret guarantees that the packets were forwarded through an established NAS-RADIUS server relationship.