DIAMETER : Why CER/CEA messages cannot be proxied /relayed/redirected ?

Question

Recently I have faced situation described below. Please ignore the dots - there is no table so I could present this in a proper table form.

The question is, when the GGSN/PCEF is establishing the session on TCP level to exchange Capabilities with Diameter Peer, who should be sending the FIN? Or maybe the FIN should not be sent at all?

In the below example, is what I saw in .pcap trace. Strange for me is there is not FIN present just FIN-Ack in this situation.

This was a issue, as I was given different IP for PCRF but I was told "everything else is the same" but it wasnt - the peer name was different.

Packet No......Direction.......Packet/message
1..............Out.............Syn
2..............In..............Syn-Ack
3..............Out.............Ack
4..............Out.............CER (diameter)
5..............In..............Ack of CER (tcp)
6..............In..............CEA (diameter)
7..............Out.............Ack of CEA (tcp)
8..............Out.............***FIN-Ack***
9..............In..............Ack

Answer 1

Hi Harshita,
As you know for CER CEA to happen both the nodes must have info about each other.
The basic need of CER/CEA is to exchange the capabilities of each other.
Now coming to the question, as you know proxy or relay nodes does not support any particular application and they just pass on the message. Also if you will proxy the message how will the proxy node get to know where to send the message.
Also, I think destination realm and destination host avp are not there in CER

Comments

Thanks Peeyush. I got the answer. Yes you are right , CER/CEA messages don't have Destination-Host and Destination-Realm AVPs.