The Diameter protocol has been selected by the telecommunications industry as the Authentication, Authorization and Accounting (AAA) protocol for the future. This Pocket Guide is your reference to the Diameter Base Protocol as defined by the Internet Engineering Task Force (IETF) in RFC 6733. This guide can be used by anyone involved with implementation, development or study of Diameter-based capabilities. Diameter is currently being used in VoIP networks for both on and off line billing/accounting applications. Diameter was also selected by 3GPP as the AAA protocol for the widely expanding LTE networks. We hope you find the Diameter Base Protocol Pocket Guide helpful.