Diameter Protocol : Easy understand the basic functionality 2020

Diameter protocol was created on 1998 to be a successor of RADIUS protocol, the main goal was to create a protocol more secure and implemented on signalling network.

It can use TCP or SCTP at transport layer and as TLS and DTLS for transport layer security and it has a fail over mechanism using internal watchdogs.

Diameter Protocol Stack

It has another mechanism to discover peers and configure them in order to maintained the sessions bindings.

Diameter communicate as a client and a server

Diameter Protocol RFCs

  • First RFC 3588
  • Additional Updates RFC 5729, 5719, 6408
  • The RFC 6733 made all other obsolete.

RFC 6733 Specifies

  • Protocol Format
  • Transport
  • Peer Connection
  • User Sessions
  • Accounting

Types of Nodes

  • Clients
  • Servers
  • Agents


Any device using the Diameter protocol stack.


A Diameter client is any device who trigger a request to a server requesting information about the user and its level of access on the local or roaming network (AAA).

Types of Diameter Clients

  • MME
  • PCEF


Handles AAA requests

  • PCRF
  • HSS

Diameter Agents


Route messages without change them


Route a message and can change it


Just simple redirect the traffic


Converts into another protocol

DEA Diameter Edge Agent

Located at border network

DRA Diameter Routing Agent

Core network providing routing capabilities

IWF Node

Convert into another protocol

DSC Diameter Signaling Controller

Groups DEA / DRA / IWF into one single device.

Diameter Applications

Diameter type of Messages

Diameter Interfaces


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