s the load. The SCP can be deployed in a centralized or distributed manner. Similarly, more than one SCP can be present in the communication path between the producer and consumer services. To ensure that multiple SCPs can route messages between a producer and consumer, the SCP can also register its profile in the NRF. Alternatively, a local configuration should also be supported. It can be deployed at a PLMN level, shared slice level, or slice-specific level with the condition that the SCP can communicate with the appropriate NRF. The NSSAAF The Network Slice Specific Authentication and Authorization Function (NSSAAF) is used for slice-specific authorization and authentication with an AAA server, which can be hosted either by the host PLM or by a third party that has a business relationship with the host operator, such as a slice dedicated to a particular enterprise. This is executed with the help of the EAP framework. The AMF performs the role of the EAP authenticator and communicates with the AAA server via the NSSAAF. The NSSAAF is responsible for any AAA protocol-related interworking with the AAA protocol supported by the AAA server. End-to-End Architecture Components, Concepts, Security, and Transport The procedure of NSSAA is triggered by the AMF during a registration procedure when a certain network slice requires slice-specific authentication, when there is a subscription change, or when the AAA server requires a re-authentication. In previous sections, we have learned about the key components of a 5G network, explored their role and responsibility, and how they interwork with each other. In the next section, we will cover some key 5G network concepts that are used. 5G network concepts In this section, we will go over the various new concepts and terminologies introduced with 5G. PDU sessions A PDU session is the logical connection between the UE and the data network. It is by the means of this logical connection that the UE is able to browse data, place calls, and SO on. QoS Flow 1 PDU Session 1 QoS Flo