Section: 16.3a.2 Accounting Update
Content: During the life of an IP-CAN bearer some information related to this bearer may change. Upon occurrence of the following events, the P-GW may send RADIUS Accounting Request Interim-Update to the AAA server: RAT change, S-GW address change and QoS change. Interim updates are also used when the IPv4 address is allocated/released/re-allocated for deferred IPv4 addressing for the PDN type IPv4v6. When the P-GW receives a signalling request (e.g. Modify Bearer Request in case of GTP-based S5/S8) that indicates the occurrence of one of these chargeable events, the P-GW may send an Accounting Request Interim-Update to the AAA server to update the necessary information related to this bearer. The P-GW need not wait for the RADIUS AccountingResponse message from the AAA server before sending the response for the triggering signalling message (e.g. Modify Bearer Response). The P-GW may delete the bearer if the AccountingResponse is not received from the AAA. The P-GW may also send interim updates at the expiry of an operator configured time limit. The following Figure 25a.2 is an example message flow to show the procedure of RADIUS accounting update, which applicable for GTP based S5/S8: Figure 25a.2: RADIUS accounting update for Modify Bearer Request