Section: 4.7.1 PDN connectivity service
Content: The Evolved Packet System provides connectivity between a UE and a PLMN external packet data network. This is referred to as PDN Connectivity Service. The IP PDN Connectivity Service s the transport of traffic flow aggregate(s), consisting of one or more Service Data Flows (SDFs). NOTE: The concept of SDF is defined in the context of PCC, TS 23.203[ Policy and charging control architecture ]  [6], and is not explicitly visible in the NAS signalling. A PDN connection to an SCEF has the following characteristics: - It is only supported for WB-EUTRA, LTE-M and NB-IoT RAT types; - It applies only when Control Plane CIoT EPS Optimisation are applicable; - It does not support the transport of traffic flow aggregate(s); - It does not support Emergency Services.