Hi Guys This might be off topic but I was wondering if someone with more knowledge than me, would be able to confirm the following :- In a mobile network scenario with thousands of IoT devices On our radius servers, we've been noticing a lot of 0-byte sessions on our databases and upon investigation, we've seen the following behaviour :-
Authentication Request Received < Access Accept sent back Accounting Start Packet Received with a Acct-Session-Id < Acknowledgement sent back Interim Accounting Packet Received - This time with a different Acct-Session-Id for the same connection
** At this point, things start going bad as we are not able to update the original DB entry created with the Acct Start Packet, since the Acct-Session-Id differs between the packet received in the Accounting Start Packet and the Interim Accounting Packet. This results in a 0-session entry in the DB for the Accounting Start Packet entry as a new entry is written into the DB based on the new Acct-Session-Id received in the Interim Accounting packet. Any subsequent packets received with a different Acct-Session-Id, results in writing a new DB entry when the Interim Accounting Packet is received. We queried this with the upstream provider, and they advised that the 3GPP-NSAPI number changes when packets are received and they claim that the Acct-Session-Id on their side would change based on the 3GPP-NSAPI value that could (and in most cases) changes. < Acknowledgement Sent back
From what I've been reading, The Acct-Session-Id should remain constant for the entire PDP context/session, even when the NSAPI changes because the Acct-Session-Id is meant to uniquely identify the entire user session. NSAPI changes are considered sub-sessions within the main PDP context and keeping the same Acct-Session-Id helps maintain session continuity for billing and tracking purposes, which is exactly our use case for accounting which is not working as expected.
Any thoughts and insights would be appreciated if someone faced a similar situation. Many thanks, Gabriel