The mappings are stored in the respective nodes performing the mapping for the duration of the session. The IP flows are identified by the UE and the PDN-GW by uplink and downlink packet filters respectively. So the aggregated IP flows constituting a bearer are carried from the UE over the radio interface to eNodeB, from eNodeB to the Serving Gateway, and then onwards to the PDN Gateway as on a single logical bearer with the same level of QoS (or packet forwarding characteristic) [11]. 3.9.1.2 QoS Parameters Each data flow (bearer) is associated with a QoS profile consisting of the following downlink related parameters [14,21]: Allocation retention priority (ARP). Proxy Mobile IP standard is currently under development; it provides similar functionality to that of Mobile IP, however it does not require any modifications to the mobile host's network stack, i.e. the mobility is taken care of by the network. 17 S8 is inter-PLMN (public land mobile network) variant of S5. Next Generation Mobile Communications Ecosystem Guaranteed bit rate (GBR). QoS class identifier (QCI). Aggregate Maximum Bit Rate (AMBR). The GBR parameter is only specified for GBR bearers and it is identified as the bit rate that can be expected to be provided by a GBR bearer. The MBR (Maximum Bit Rate) limits the bit rate that can be expected to be provided by a GBR bearer (e.g., excess traffic may get discarded by a rate shaping function). The ARP parameter, being an integer in the range 1-16, is defined primarily for prioritization when conducting admission control decisions. The QCI is a scalar to a more detailed set of QoS attributes listed in Table 3.9. The QCI includes parameters like layer 2 packet delay budget and packet loss rate in addition to the relative priorities between GBR and non-GBR resource types. Each APN 18 (access point name) access by a UE is associated with APN-AMBR. The APN AMBR is a subscription parameter stored per APN in the HSS (Home Subscriber Server). It limits the aggregate bit rate that can be expected to be provi