Guidelines for Extending Diameter

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. Standardization efforts in Diameter have led to a number of specifications that cover a wide range of use cases. Before going into details of extending Diameter, the chapter discusses the registration policies for extensions. The Internet Engineering Task Force (IETF) has published a document listing a number of possible registration policies. An important design decision for extending Diameter is whether Diameter nodes are required to understand the new functionality or whether the newly defined features are purely optional. Whenever it is mandatory for Diameter clients, Diameter agents (except for relays and redirect agents) or Diameter servers to understand new functionality, a new Diameter application has to be defined. Most specification authors define Attribute-Value Pairs such that they can to be extended.