How a Diameter Routing Agent (DRA) Works

A Diameter Routing Agent sits at the heart of a Diameter network. It provides scalable, centralised routing of Diameter messages in a multi-vendor, multi-node environment within a service providers IMS and LTE core.

The DRA reduces complexity. Placing a DRA at the center of the network immediately simplifies the network. All nodes have a common connection and the DRA manages and optimisies the Diameter network.

The Diameter Routing Agent acts as mediation platform. It insures that different nodes in the network can interconnect successfully by manipulating and modifying the Diameter signalling.

It allows network engineers to standardise or normalise messaging in the network. For example, an Online Charging System may communicate with many nodes in the network. The DRA can be used to modify the signalling from the remote nodes into a set of standardised messages to present to the OCS.

The DRA provides Session Binding functionality. This allows the DRA to bind a particular session to an identified device or cluster of devices. For example, there may be a number of OCS platforms hosted in a network. Messaging from a device is routed to one of the OCS instances, and session binding insures that for the remainder of the session, all messages will be routed to-and-from the same OCS.

To insure the optimum management of traffic across the network a DRA provides load balancing and throttling. Load balancing is applied to distribute traffic evenly between nodes across the network. Throttling is applied to control the the volume of traffic to and from nodes. This smooth's the flow of messages around a network.

There are 3 main stages Diameter messages move through as they transit the SVI-DRA.

All incoming messages first hit the Access Control function. Messages are checked for compliance against the Diameter Protocol standards. Messages can be rejected back, or binned if they do not conform while logged and reported to the DRA management system.

Message filtering can be applied to weed out known issues comparing the contents of the message headers or AVP’s against configured black lists / white lists.

The SVI-DRA provides sophisticated throttling functionality allowing network engineers to manage the number of transactions being processed from a remote node. Incoming Requests from remote nodes are placed in an internal queue for processing.

Network engineers are able to create Transaction Criteria Records that define the number of transactions allowed over a given time period from a remote node. They can then define what happens if these limits are exceeded – whether to queue, ignore or reject an incoming request. They can also prioritise chosen messages allowing them to jump to the front of the queue. Using this mechanism they are able to fine tune message flow into the network.

Messages can be manipulated using a powerful, regular-expression based module to change message header and AVP contents allowing removal, creation and replacement of contents. The message is then passed to the main Routing module.

At core of the DRA is a powerful routing module. It allows network engineers to develop complex routing scenarios allowing them to route on any combination of message header and AVP contents.

Once a Routing decision has been made the message is passed to the Outbound Control module which allows, if required, a further round of message manipulation. Throttling and message prioritisation can also be applied by the network engineer to optimise outbound messaging based on the far end nodes characteristics and performance capabilities.

The key to optimal network management is flexibility. The functionality outlined so far is standard product functionality in the DRA fully configurable through the DRA’s web-based GUI.

The Mediation Engine enables a set of rules to be constructed that allow, on the triggering of a defined condition, a number of actions to take place. These rules are stored as Mediation Policies. These can be triggered at many points during the flow of a message through the DRA.

The DRA is a key component in the successful management and evolution of today's Diameter Networks.

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