Diameter

7Guidelines for Extending Diameter

7.1 Introduction

This chapter discusses an advanced topic of interest to those who have worked in standardization, have written Diameter implementations, or who have used Diameter to solve specific business problems. As discussed throughout this book, standardization efforts in Diameter have led to a number of specifications that cover a wide range of use cases. Still, you may have reached a point where the existing functionality does not cover your use case or it does not completely fulfill your requirements. You may have come to the conclusion that you need to extend the Diameter protocol. You are most likely asking yourself the following question: “Why cannot I extend the protocol in any way I want?”

To answer that question it is useful to provide some background information about the work in the Internet Engineering Task Force Diameter Maintenance and Extensions (DIME) working group. The working group suggests reusing as much as possible for the following reasons:

• The time to finalize a specification writing effort is significantly reduced since prior work can be taken into account. While it appears that writing specifications is fairly easy it still requires several months to years. The 80/20 rule applies: 80% of the time is spent on 20% of the specification.
• Reuse will lead to a smaller implementation effort. You will be able to make use of existing libraries (such as parsers). This does, however, require that your Diameter stack is written ...