Section: 13a.2.2.3 Creation of a PDP Context/EPS Bearer for IMS Media Flows
Content: For PDP Contexts/EPS bearers used to carry IMS media flows, specific policies may be applied. The policy includes packet filtering, which enables a specific charging for these PDP Contexts/EPS bearers, see 3GPP TS 29.212[ Policy and Charging Control (PCC); Reference points ]  [75]. The creation of a PDP Context/EPS bearer to be used to carry media flows involves interaction between the MS/UE and the GGSN/P-GW and between the GGSN/P-GW and the PCRF. The interaction between the GGSN/P-GW and the PCRF, i.e. the Gx interface, is described in detail in 3GPP TS 29.212[ Policy and Charging Control (PCC); Reference points ]  [75]. The interaction between the MS/UE and GGSN/P-GW is described in 3GPP TS 29.213[ Policy and charging control signalling flows and Quality of Service (QoS) parameter mapping ]  [76]. If Gx is enabled for the APN, the GGSN/P-GW contacts the PCRF selected during the establishment of the APN.