EPS bearer, in order to be delivered to the UE. SDFs with the same QoS class are delivered, as aggregated, through an EPS bearer, whereas the ones with different QoS class are delivered through dif- ferent EPS bearers. In LTE, there are two types of EPS bearers, default and dedicated. When a UE attaches to the LTE network, an IP address is assigned for PDN connection and a default EPS bearer is established at the same time [58,59]. In an LTE network, the QoS parameters are defined at service and bearer levels. SDF QoS parameters are service-level QoS parameters, whereas EPS bearer QoS parameters are bearer-level QoS parameters. Service level and bearer level are also called as SDF level and SDF aggregate level, respectively. An SDF aggregate refers to a group of SDFs which have PDN connection (EPS session) UE IP address Default EPS bearer SDF1 QoS policy IP flow 1 SDF2 QoS policy IP flow 2 IP flow 3 SDF3 QoS policy Dedicated EPS bearer IP flow 4 SDF4 QoS policy IP flow 5 Figure 1.84 QoS architecture and process in LTE [59]. 5G Network Architecture 173 the same QCI and ARP values and belong to one EPS session. Both QCI and ARP are the basic QoS parameters applied to all SDFs and EPS bearers. The QoS class identifier (QCI) is particularly important because it serves as a reference that indicates the performance characteristics of SDFs and EPS bearers. In addition to these two basic parameters, there are other QoS parameters, such as GBR, maximum bit rate (MBR), and aggregated maxi- mum bit rate (AMBR) that specify the bandwidth (or bit rate) characteristics of SDFs and EPS bearers. The SDF and EPS bearer QoS parameters are as follows: SDF QoS parameters (QCI, ARP, GBR, and MBR) and EPS bearer QoS parameters (QCI, ARP, GBR, MBR, APN-AMBR, and UE-AMBR). The QCI and ARP are applied to all EPS bearers. An EPS bearer is classified as a GBR bearer or a non-GBR bearer depending on the resource type specified by its QCI. A default bearer must be non-GBR, while a dedicated bearer can be either GBR or non-GBR. Other than QCI