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
7.4.Sendmessage API SUCCESS
SendMessage API is SUCCESS by sending valid Diameter message parameter, its prerequisite are Initialization API, StartConnection API and StartSession API are
SUCCESS; sending CER message.
Figure 8: SendMessage CER SUCCESS
Figure 9: SendMessage DWR SUCCESS