Getting RST from diameter after Capabilities-Exchange-Answer

Question

We are connecting the PCEF to PCRF. But the Gx link is not coming up. I have observed that there are CER/CEA successful between PCEF a PCRF. DWR is generated by PCRF (i.e. seen in the logs) but it is not sent (i.e. not seen in the capture). Any suggestion on what could be the issue.

Comments

Let me understand your problem -

 1. PCEF sends the CER
 2. PCRF sends CEA with a success result
 3. PCEF receives this CEA and closes the connection.

Any log on the PCEF side indicating why it is closing the connection? As it would be useful to get the information of what the issue is from that other peer for debugging.

Answer 1

Are the two sides using the same Diameter implementation? We have seen implementation doing things differently, causing capabilities exchange to fail - especially, check the supported application ids/VSAIs. At least one implementation sends DIAMETER_SUCCESS in CEA but does NOT fill in application ids.
If the other side sticks to the standard, it will end up closing the connection.

Answer 2

The fact that you are seeing CEA with Success means that the peer ends have agreed upon the Application ids and the VS attribs. Moreover you are even seeing the DWR being generated at PCRF.
I think somehow your DWR is not being sent out therefore the PCEF is timing out and RSTing the connection.

May sound wierd, but can you check your IP route table to see if there are ambiguous routes (especially through different interfaces) to the PCEF? There have been such instances where some requests/keepalives are sent, but take a different path and never reach the other end, thereby flaking up and down the connections.

Another approach would be, use a simulator (if you readily have one) to simulate your endpoint(depends on whom you suspect, the PCEF or PCRF) and see if the same behaviour occurs.

Run continous ping from one end to another and see if there are any packet losses.