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Diameter

Site: Saylor Academy
Course: CS406: Information Security
Book: Diameter
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Date: Saturday, 19 April 2025, 7:47 AM

Description

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.

Table of contents

Abstract

The DIAMETER protocol is designed to provide an Authentication, Authorization and Accounting (AAA) framework for applications such as network access or IP mobility and also intended to work in local Authentication, Authorization & Accounting and roaming situations.

The Diameter protocol was initially developed by the Internet Engineering Task Force (IETF) as an Authentication, Authorization, and Accounting (AAA) framework Diameter was further embraced by the Third Generation Partnership Project (3GPP) as the key protocol for AAA and mobility management in 3G networks.

The DIAMETER protocol consists of a base protocol, defined in [RFC 3588] September 2003 and it is obsolete by [RFC 6733] October 2012, and set of applications (also called extension of the base protocol). The base protocol must be supported by all applications. The base protocol must be supported by all applications.

Keywords: DIAMETER, RADIUS, AAA, IMS, SIP

Source: V. A. Sowmya, Nagarathna, and Ajay Satyanarayana, http://52.172.159.94/index.php/ijird/article/view/36576
Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 License.

1.Introduction

DIAMETER is the newest AAA protocol developed in 2001 from the older AAA protocol RADIUS (Remote Access Dial-In User Service) by the Internet Engineering Task Force (IETF) as an Authentication, Authorization, and Accounting (AAA) framework intended for applications such as remote network access and IP mobility. The DIAMETER protocol was developed to resolve the issues that RADIUS left open. In new application areas like Wireless Local Access Network (WLAN) and Voice over IP (VoIP), DIAMETER is better suited and gives better support for roaming users. DIAMETER is defined as a base protocol used in conjunction with a set of applications. The Diameter Base Protocol [RFC 6733] contains the basic functionality like reliable transport, message delivery and error handling. The Diameter applications are extensions of the basic functionalities that are tailored for a particular usage in a particular environment.

AAA Framework includes: 

  •  Authentication is the verification of the identity of the entity. 
  •  Authorization is the determination whether the requesting entity is allowed access to a particular resource. 
  •  Accounting is the collecting of information about resource usage for the purpose of capacity planning, auditing, billing or cost allocation.

2.IP Multimedia Subsytem


Figure 1: architecture of IMS


IP Multimedia Subsystem or IMS is a standardized Next Generation Networking (NGN) architecture for telecom operators that want to provide mobile and fixed multimedia services. It uses a Voice-over-IP (VoIP) implementation based on a 3GPP standardized implementation of Session Initiation Protocol (SIP), and runs over the standard Internet Protocol (IP). Existing phone systems (both packet-switched and circuit-switched) are supported.

The IMS is the technology that will merge the Internet with the Cellular world. It is network enables and drives efficient converged service offerings. It is the key to delivering multimedia services with telecom-grade quality of service across fixed and mobile accesses. It creates new opportunities for operators who want to deliver attractive, easy-to-use, reliable and profitable multimedia services – including voice, pictures, text and video, or any combination of these – with existing services such as web, email, instant messaging, and videoconferencing available nearly everywhere. The IMS is based on a horizontally layered architecture, consisting of three layers, namely, Service Layer, Control Layer, and transport Layer.

(i) Service Layer comprises application and content servers to execute value-added services for the user.

(ii)Control layer comprises network control servers for managing call or session set-up, modification and release. The most important of these is the Call Session Control Function (CSCF).

(iii)Connectivity Layer comprises of routers and switches, for both the backbone and the access network Device layer consists of user terminal devices like UE (user equipment), PDA, Desktop, and Laptop which can connect to the IMS network.

Figure 2: Reference point in IMS




3.Diameter Protocol Stack Architecture


Figure 3: Architecture of Diameter Protocol Stack


The above shows the schematic of DIAMETER protocol stack architecture for application server in IP Multimedia subsystem (IMS).

  • Diameter base protocol: The Diameter base protocol provides basic services to one or more applications (also called functions) that each runs in a different Diameter instance.

  • Basic functionalities provided by base protocol are as follows: reliable transport, message delivery, Delivery of AVPs, Capability Negotiation, Error Notification, Accounting, and extensibility via new command codes and AVPs.

  • Diameter Client API (Application programming interface): This acts as the interface between the diameter base protocol and the diameter application.

  • Diameter application: Diameter application is an application specific protocol used for transfer of application specific functions and messages.

  • Diameter applications are namely as follows: NASREQ, EAP, Mobile IPV4, Credit Control and other 3GPP interfaces like Cx, Dx, Sh, Ro, Rf etc

4.Implementation Of Diameter Protocol Stack

Implementation begins with the sequence of development of the diameter base protocol and as well as the corresponding required diameter application protocol.

API is another important development which acts as interface between the diameter base and its corresponding diameter application protocol. DIAMETER is application layer protocol comes under TCP/IP protocol suite and it runs over reliable transport protocols, TCP (Transmission Control Protocol) and TLS (Transport Layer Security).

5.Flow Diagram

Figure 4: API Flow of Diameter Client

6.Diameter Client API

Diameter Client API is used to perform the vital operations carried out in Diameter Core functionalities and acts as an interface for the Diameter Base Protocol and Diameter Application.

6.1.Initialization API

Initialization API used to initialize the DIAMETER Client stack which performs in the registration of the stack with TCA, allocate the memory for the stack resources and configuration of the stack.

6.2.Start Connection API

StartConnection API is used for the connection establishment between DIAMETER client and DIAMETER server which deals with the creation of transmission sockets, timers.

6.3.Startsession API

StartSession API is used for the session establishment between the connected DIAMETER client and DIAMETER server which deals with the creation sessions and filling details.

6.4.Sendmessage API

SendMessage API is used to send the Diameter message packet in encoded form to another Diameter Node (Diameter Server) in allotted Connection_ID and Session_ID; by creating new transaction using Transaction_ID. Flow Diagram of this API is given in Figure 4.

6.5.Terminatesession API

TerminateSession API is used to terminate the session which has been established between the connected DIAMETER client and DIAMETER server which deals with the deletion of sessions and its details.

6.6.Terminateconnection API

TerminateConnection API is used for the terminating the connection established between DIAMETER client with the DIAMETER server which deals with the deletion of transmission sockets, timers.

6.7.Uninitialization API

UnInitialization API used to uninitialize the DIAMETER Client stack which perform deregistration of the stack with TCA, de-allocate the memory allotted for the stack resources and configuration of the stack.

7.Result

Snapshots of all APIs are given as follows:

7.1.Initialization Api Success

Initialization API is called with valid parameter value resulting in SUCCESS of Initialization of Stack.


Figure 5: Initialization API SUCCESS

7.2.Startconnection API SUCCESS

StartConnection API is called resulting in SUCCESS, whose pre-requisite is Initialization API which is SUCCESS; later UnInitialization is called which is SUCCESS.

Figure 6: StartConnection API SUCCESS

7.3.Startsession API SUCCESS

StartSession API is SUCCESS, and its pre-requisite are Initialization API and StartConnection API is SUCCESS; later UnInitialization is called which is SUCCESS.

Figure 7: StartSession API SUCCESS

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

7.5.Terminatesession API SUCCESS

TerminateSession API is called resulting in SUCCESS, and its pre-requisite is Initialization API and StartConnection, StartSession API are SUCCESS; later remaining APIs are called which all are SUCCESS.

Figure 10: TerminateSession API SUCCESS

7.6.Terminateconnection API SUCCESS

TerminateConnection API is called resulting in SUCCESS, and its pre-requisite is Initialization API, StartConnection and/or StartSession API are SUCCESS; later terminate the connection and sessions (if present) by TerminateConnection API and later UnInitialization is called both are SUCCESS.

Figure 11: TerminateConnection API SUCCESS with TerminateSession Called before TerminateConnection



Figure 12: TerminateConnection API SUCCESS without TerminateSession Called before TerminateConnection


7.7.Uninitialization API SUCCESS

UnInitialization API is called (having no parameter) resulting in SUCCESS of UnInitialization of Stack by de-allocating all its resources.

Figure 13: UnInitialization API SUCCESS