Diameter

2Fundamental Diameter Concepts and Building Blocks

2.1 Introduction

This chapter covers the basic concepts of Diameter, describing the types of nodes that participate in Diameter sessions and the format of Diameter messages. It also provides an overview of Diameter sessions and error handling.

2.2 Diameter Nodes

As mentioned in Chapter 1, Diameter nodes are auxiliary participants in larger networks that offer various services to end users. A Diameter node is a software application that implements the Diameter protocol to provide authentication, authorization, and accounting services to entities or devices requesting or using network services. Two Diameter nodes that share a direct transport connection with each other are called Diameter peers. A Diameter node can act as a client, server or agent:

• Client

  A Diameter client creates Diameter messages to request authentication, authorization, and accounting services for network users. The behavior of a Diameter client depends on the application it is supporting. A Diameter client is sometimes known as a network access server, which can be confusing. However, from a user perspective, the NAS is a server since a user interacts with it to gain access to the network, but within the Diameter framework it is an application client.

• Server

  A Diameter server receives and handles authentication, authorization, and accounting requests for a particular realm or administrative domain. A Diameter server supports specific Diameter applications, in addition ...