Section: 4.4.3.3 PDN GW
Content: The PDN GW is the gateway which terminates the SGi interface towards the PDN. If a UE is accessing multiple PDNs, there may be more than one PDN GW for that UE, however a mix of S5/S8 connectivity and Gn/Gp connectivity is not supported for that UE simultaneously. PDN GW functions include for both the GTP-based and the PMIP-based S5/S8: - Per-user based packet filtering (by e.g. deep packet inspection); - Lawful Interception; - UE IP address allocation; - Transport level packet marking in the uplink and downlink, e.g. setting the DiffServ Code Point, based on the QCI, and optionally the ARP priority level, of the associated EPS bearer; - Accounting for inter-operator charging: for home routed roaming, the P-GW shall collect and report the uplink and downlink data volume (per EPS bearer) as received from and sent to the serving node; - UL and DL service level charging as defined in TS 23.203[ Policy and charging control architecture ]  [6] (e.g. based on SDFs defined by the PCRF, or based on deep packet inspection defined by local policy); - Interfacing OFCS through according to charging principles and through reference points specified in TS 32.240[ Telecommunication management; Charging management; Charging architecture and principles ]  [51]. - UL and DL service level gating control as defined in TS 23.203[ Policy and charging control architecture ]  [6]; - UL and DL service level rate enforcement as defined in TS 23.203[ Policy and charging control architecture ]  [6] (e.g. by rate policing/shaping per SDF); - UL and DL rate enforcement based on APN-AMBR (e.g. by rate policing/shaping per aggregate of traffic of all SDFs of the same APN that are associated with Non-GBR QCIs); - DL rate enforcement based on the accumulated MBRs of the aggregate of SDFs with the same GBR QCI (e.g. by rate policing/shaping); - DHCPv4 (server and client) and DHCPv6 (client and server) functions; - The network does not support PPP bearer type in this version of the specification. Pre-Release 8 PPP functionality of a GGSN may be implemented in the PDN GW; - The PDN GW may support Non-IP data transfer (e.g. with CIoT EPS Optimisations); - The PDN GW (when acting as a combined PDN GW+SMF as specified in TS 23.501[ System architecture for the 5G System (5GS) ]  [83]) may support Ethernet data transfer; - packet screening; - sending of one or more "end marker" to the source SGW immediately after switching the path during SGW change; - PCC related features (e.g. involving PCRF and OCS) as described in TS 23.203[ Policy and charging control architecture ]  [6]. Additionally the PDN GW includes the following functions for the GTP-based S5/S8: - UL and DL bearer binding as defined in TS 23.203[ Policy and charging control architecture ]  [6]; - UL bearer binding verification as defined in TS 23.203[ Policy and charging control architecture ]  [6]; - Functionality as defined in RFC 4861 [32]; - Accounting per UE and bearer. The P-GW provides PDN connectivity to both GERAN/UTRAN only UEs and E-UTRAN capable UEs using any of E-UTRAN, GERAN or UTRAN. The P-GW provides PDN connectivity to E-UTRAN capable UEs using E-UTRAN only over the S5/S8 interface.