Section: 16.3.3 Accounting Update
Content: During the life of a PDP context some information related to this PDP context may change (i.e. SGSN address if a Inter-SGSN RA update occurs). Upon reception of an UpdatePDPContextRequest from the SGSN, the GGSN may send an Accounting Request Interim-Update to the AAA server to update the necessary information related to this PDP context (see figure 24). Interim updates are also used when the IPv4 address is allocated/released/re-allocated for deferred IPv4 addressing for the PDP type IPv4v6. If the GGSN receives an UpdatePDPContextRequest from the SGSN that specifically indicates a direct tunnel establishment or a direct tunnel teardown (switching the user plane tunnel end back to the SGSN), and only the GTP user plane address and/or the GTP-U TEID have changed, then the GGSN should not send the Accounting Request Interim-Update to the AAA server. In such cases, the GGSN need not wait for the RADIUS AccountingResponse from the AAA server message before sending the UpdatePDPContextResponse to the SGSN. The GGSN may delete the PDP context if the AccountingResponse is not received from the AAA. NOTE: As shown the GGSN need not wait for the RADIUS AccountingResponse from the AAA server message to send the UpdatePDPContextResponse to the SGSN. The GGSN may delete the PDP context if the AccountingResponse is not received from the AAA. Figure 24: RADIUS for PDP context Update