Diameter

3Communication between Neighboring Peers

3.1 Introduction

This chapter describes in detail the principles of both transport and Diameter‐level connectivity between two adjacent Diameter nodes, known as peers. This chapter covers how the peers discover each other, how the peers connect and maintain connections, and how transport failures are handled. The chapter also covers advanced transport topics such as multi‐homed connections, head‐of‐line blocking, and multiple connection instances.

3.2 Peer Connections and Diameter Sessions

Two Diameter nodes that have a direct transport protocol connection between each other, known as a peer connection, are considered Diameter peers. The peer connection does not need to be directly connected from the IP point of view; there may be zero or more IP routers between the Diameter peers. Figure 3.1 shows a simple network topology where two peers are connected over an arbitrary IP network.

Figure 3.1 Diameter and transport connection between two peers.

The two peers may also establish a Diameter user session between each other. However, it is not required that a peer connection map directly to a Diameter session. Figure 3.2 shows a simplified network topology where Diameter nodes A and B have a Diameter user session that consists of multiple peer connections through an intermediating Diameter agent C.

Figure 3.2 Diameter user sessions and peer connections. ...