Question

I have 3 simple questions.

1. What is the Diameter protocol in simple explanation?
2. Why is it used?
3. How can one use it?

I have searched the net for a practical explanation but couldn’t find one. All there is, is some technical blabber.

Answer 1

I found this complete article on Diameter protocol written in IBM website.

Introduction

The Diameter protocol was derived from the RADIUS protocol with a lot
of improvements in different aspects, and is generally believed to be
the next generation Authentication, Authorization, and Accounting
(AAA) protocol. The Diameter protocol was widely used in the IMS
architecture for IMS entities to exchange AAA-related information.
Because the IMS system might be the next big thing in the telecom
industry, we believe a clear understanding of the Diameter protocol is
necessary for understanding the essence of the IMS architecture. This
article offers an overview of Diameter and how it works. For
developers interested in how AAA in IMS works, or who want to
implement Diameter applications, this article is a good starting page.

With the emergence of new technologies and applications such as
wireless networks and mobile IPs, the requirements for authentication
and authorization have greatly increased, and access control
mechanisms are more complex than ever. The existing RADIUS (Remote
Authentication Dial-In User Service) protocol can be insufficient to
cope with these new requirements; what’s needed is a new protocol that
is capable of fulfilling new access control features while keeping the
flexibility for further extension. This is where the Diameter protocol
comes into play.