RADIUS

Packet Formats

The RADIUS protocol uses UDP packets to pass transmissions between the client and server. The protocol communicates on port 1812, which is a change from the original RADIUS RFC document. The first revision specified that RADIUS communications were to take place on port 1645, but later this was found to conflict with the “Datametrics” service.

RADIUS uses a predictable packet structure to communicate, which is shown in Figure 2-1.

Figure 2-1. A depiction of the RADIUS data packet structure

The data structure is broken down into five distinct regions, which are discussed later in this chapter.