S-GW and P-GW, perform QoS enforcement as policy enforcement points (PEPs). On one side, the S-GW performs QoS control at the IP packet level, while on the other side P-GW provides QoS and policy enforcement at the service level. S-GW serves also as anchor node for connection 4G mobile network External IP networks E-UTRAN eNodeB Remote peer node End-to-end service bearer EPS (Evolved packet system) bearer External bearer LTE/LTE-A radio S5/S8 S1 bearer bearer bearer E-UTRAN - Evolved UMTS terrestrial access networks EPC - Evolved packet core P-GW - Packet data network gateway S-GW - Serving gateway UE - User equipment Figure 5.7 QoS support in LTE/LTE-Advanced mobile networks. 5.3 QoS in 4G Ultra-Broadband: LTE-Advanced-Pro of previous 3GPP RANs to the EPC, which include UTRAN (for UMTS) and GERAN (Global System for Mobile communication EDGE Radio Access Network, that is, 2.5G from 3GPP). However, for non-3GPP IP networks (e.g. WiFi, WiMAX), the mobility anchor point is the P-GW. The bearers in 3GPP mobile networks are based on IP traffic tunneling in the EPS with GTP, which in fact started with GPRS (as 2.5G) and further was well established with UMTS (as the 3G technology) and then continued in 4G mobile networks from 3GPP. Regarding 4G bearers, GTP-U tunnels are established for carrying user data traf- fic between the eNodeBs and S-GW as well as between S-GW and P-GW. In fact, S-GW acts as the GTP-U relay between the eNodes and the P-GW. On the other side, GTP-C tunnels are established between S-GW and MME (for the signaling related to handovers, due to mobility of the mobile users) and between S-GW and P-GW. Also, for fast han- dovers there is a GTP-U tunnel established between adjacent eNodeBs to transfer the IP packets from the old eNodeB (before the handover) and the new eNodeB (after the handover), i.e. for fast path switching (between S-GW and the mobile terminal) through the EPS at the handover events. One should note that in LTE/LTE-Advanced mobile networks besides the bearers there is an option to use