 the core network interfaces. For CSPs that view 5G as an opportunity for transformative change both in terms of functionality and cost per bit, a service-based interface instead of point-to-point interfaces looks more attractive. The challenge with the point-to-point architecture is that it contains many unique, or quasi-unique, interfaces between functional elements, each connected to multiple adja- cent elements. This "tangle" of connections creates dependencies between functions and makes it difficult to change the deployed architecture. If a new function is introduced, or an existing function expanded or upgraded, the operators needs to reconfigure mul- tiple adjacent functions and test the new configuration before going live. This raises the business cases thresholds to experiment with, and deploy, new services. In effect, the end user service is tied to the network, and consequently the operator's addressable market is artificially limited. This is acceptable where the service set is well defined and relatively fixed (voice, broadband, etc.), but in the 5G era, where operators expect to offer a multitude of diverse services that must be able to adapt to fast-changing demand or industry-specific requirements, a more dynamic and agile architecture is needed. The SBA decouples the end user service from the underlying network and platform infrastructure, and in doing so, enables both functional and service agility. By virtue of the SBA operating on a cloud-native foundation, it is much simpler for an operator to add, remove, or modify virtual network functions (VNFs) from a network processing path (functional agility) and create new service paths on demand (service agility). 3GPP has selected SBA for application in the 5G Core Control Plane (the middle part of Figure 5.4. Service-based interfaces are all based on HTTP and are all denoted with the legend Nxxx in Figure 5.4. 5.3.1 Access and Mobility Management Function The Access and Mobility Management Function (AMF) is part of the control plane pro- cessing o