Diameter is used extensively in 3GPP networks (Especially LTE) to provide the AAA services.

The Diameter protocol is great, and I’ve sung it’s praises before, but one issue operators start to face is that there are a lot of diameter peers, each of which needs a connection to other diameter peers.

This diagram is an “Overview” showing one of each network element – In reality almost all network elements will exist more than once for redundancy and scalability.

What you start to end up with is a rats nest of connections, lines drawn everywhere and lots of manual work and room for human error when it comes to setting up the Diameter Peer relationships.

Let’s say you’ve got 5x MME, 5x PCRF, 2x HSS, 5x S-SCSF and 5x Packet Gateways, each needing Diameter peer relationships setup, it starts to get really messy really quickly.

Enter the Diameter Routing Agent – DRA.

Now each device only needs a connection to the DRA, which in turn has a connection to each Diameter peer. Adding a new MME doesn’t mean you need to reconfigure your HSS, just connect the MME to the DRA and away you go.

I’ll cover using Kamailio to act as a Diameter routing agent in a future post.