E marks uplink packets over the radio air-interface with the QoS flow ID for the purpose of marking forwarded packets to the core network. Downlink traffic is marked to enable priori- tization in the IP network and in the access node. Similar traffic marking may be used for uplink traffic, according to the operator's configuration. Standardized packet marking informs the QoS enforcement functions of what QoS to provide without any QoS signaling, although the option with QoS signaling offers more flexibility and QoS granularity. 1.2.1.2.2 Radio Network Identifiers Each entity and bearer in NG-RAN and 5GC are identified with a unique identifier. The identifiers are either permanently provisioned, such as the International Mobile Subscriber Identity (IMSI) and International Mobile Equipment Identity (IMEI) that are assigned by an operator to the UE, or they are assigned during the lifetime of UE operation in an operator's network. Fig. 1.56 illustrates the identities that are either provisioned or dynamically/semi- statically assigned to the bearers and the entities in 5GS. This section describes the bearers and identifiers that have been introduced in 3GPP 5G specifications. The direction of the arrows in the figure indicates the entity which assigns the identifier and the entity to which the identifier is assigned. The bearers and various bearer identifiers depending on the net- work interface and the flow direction are also shown in the figure. Note that the protocols over NR-Uu and NG interfaces are divided into two categories: user-plane protocols, which Service data flow is a fundamental concept in the 3GPP definition of QoS and policy management. Service data flows represent the IP packets related to a user service (web browsing, e-mail, etc.). Service data flows are bound to specific bearers based on policies defined by the network operator. The traffic detection filters, for example, IP packet filter, required in the user-plane function can be configured either in the SMF and provided to the UPF, as service