 the eNB and MME entities and the GTPv2-C signaling, exchanged between the MME and SGW entities, are responsible for constructing this bearer. The S5 bearer is constructed between the SGW and PGW entities. The GTPv2-C signaling exchanged between the SGW and PGW entities is responsible for constructing this bearer. The connection of the radio bearer and the S1 bearer, performed by the eNB entity, constitutes the EPS radio access bearer (E-RAB). The connection of the E-RAB and S5 bearers, which is performed by the SGW entity, constitutes the EPS bearer. The PGW entity is the only EPS mobile network entity that routes traffic data (IP packets). The IP transport network that enables communication between the EPS network entities routes the S1 or S5 bearers. The eNB and SGW entities do not perform routeing. They only provide the connection between the bearers. There are two types of bearers in the EPS network: - the default bearer established when attaching the mobile, used for example to transport SIP signaling; - the dedicated bearer, established following a specific request from the mobile, used for example for transport of real time protocol (RTP) streams containing voice or video. 1.1.3.2. Quality of Service The EPS bearer can be of guaranteed bit rate (GBR) type or can be of non-GBR type. VoLTE and ViLTE Table 1.1 provides the QoS characteristics associated with these two bearer families. QoS characteristics Non-GBR QCI (QoS Class Identifier) ARP (Allocation and Retention Priority) GBR (Guaranteed Bit Rate) MBR (Maximum Bit Rate) APN-AMBR (Aggregate Maximum Bit Rate) UE-AMBR Table 1.1. QOS characteristics The QCI parameter indicates the priority level, the delay and the packet loss rate (Table 1.2). QCI from 1 to 4 are assigned to GBR bearers. QCI from 5 to 9 are assigned to non-GBR bearers. Resource Packet loss Priority Delay Examples of services 100 ms Voice 150 ms Video Calling 50 ms Games 300 ms Video. 100 ms SIP Signaling 300 ms Video, Internet 100 ms Voice, Video, Non-GBR Games 300 ms Video, Internet Table