Diameter
Read this article about the history of Diameter and why it was developed. What preceded Diameter as an authentication protocol? While you do not need to understand how Diameter authenticates, you should have a general idea of its authentication process.
7.Result
7.5.Terminatesession API SUCCESS
TerminateSession API is called resulting in SUCCESS, and its pre-requisite is
Initialization API and StartConnection, StartSession API are SUCCESS; later remaining
APIs are called which all are SUCCESS.
Figure 10: TerminateSession API SUCCESS