Overview

A customer reports an issue with the CDRs that AAA generates. They report that for the same Session ID, the usage value gets reset leading to incorrect billing/rating calculations for end subscribers. A session that progresses and spans over multiple days ideally should have incremental CDR usage but that is not what is seen:

Solution

AAA Server logs the CDRs as received from the network element. In this specific case what was seen was that the network element was sending the same Session ID even after a RADIUS Session STOP.

This can be identified by looking at the CDRs for the specific accounts where the issue was reported. 

The "ACCTSTATUSTYPE" Field in the CDR maps to the RADIUS AVP: Acct-Status-Type. This has one of the following numeric values:

1. Start: Value 1
2. Stop: Value 2
3. Interim-Update: Value 3
4. Accounting-On: Value 7
5. Accounting-Off: Value 8
6. Accounting-Delayed: Value 9
7. Accounting-Resumed: Value 13

The Correct Usage is reported in the "inputOctets" and "outputOctets' fields of the CDR and these are received from the Network Element on AVPs: Acct-Input-Octets and Acct-Output-Octets correspondingly.

When a STOP value is received the usage is reset and so subsequent Start, Interim Updates start reporting back Usage from "0" as if it is a new call.

Some BNGs are known to use the same session ID until the Router is manually restarted.

If such values are seen in the CDR then this is something that the Network element has to investigate with the reason for using the Same Session ID for subsequent Sessions. Handling these for Rating/Billing is outside the scope of product support as this is something the Mediation solution customer uses should handle.