DIAMETER: Does Proxy Agent validate presence of a mandatory field for an incoming diameter message ?

Question

Please find the description of the problem:
A diameter client and server communicates in the network through Proxy Agent.
Here, I have assumed PCEF is a diameter client and PCRF is a diameter server. Interface between the PCEF and the PCRF is known as Gx.

Does Proxy agent, which sits between PCEF and PCRF, need to support Gx application ?
Does Proxy agent validate presence of any mandatory or optional AVP when it receives a message from a diamter client (PCEF) before forwarding it to diameter server (PCRF) ?

Can someone please provides the detailed behavior of a proxy agent ?

Answer 1

A Proxy agent can be used to manage the application work and to ease the authorized decisions on behalf of other party. If we talk about any Proxy agent, It has rights to see the message that what he is going to proxy out, So in Gx reference point, yes it has to understand the Gx messages {CCR-CCA (I,U,T)} and other messages too. Precisely it should have ABNF of Gx application.

Yes, AVP level evaluation would be there. It should be. Atleast up to mandatory level. If the Proxy Product is more smart then it can also do till optional AVP evaluation but in most of the cases it considers only Mandatory . Because we can not expect that when vendor is going to add his own Vendor specific AVP's, Operators don't want to configure these info's in agent, to avoid this Proxy agent is configured up to Mandatory Level AVP.

Answer 2

In general, a proxy agent is application aware, unlike a relay or redirection agent. Depending on the actual value addition provided by the specific agent, it will have to access application AVPs. While doing this, it may validate the AVPs.

I don't think every proxy agent will have to do this, but if it depends on the missing AVPs, for its functioning clearly it is going to complain.