set of HTTP. REST is used to create web applications that provide and consume services from each other. A web service that follows the guidelines stated by REST is called a RESTful application. The main benefits of REST are the following: It makes scalable applications It improves the modifiability of applications It enhances the performance of an application It improves the simplicity of application communication It ensures the portability of applications It ensures the reliability of applications It is stateless It is HTTP-based and has a standard set of operations (Create, Read, Update, and Delete (CRUD)) It is client/server-based It is cacheable It is a layered system It has a uniform interface Let us discuss some of the aforementioned concepts. Client/server - a REST principle applicable to 5G The 3GPP 5G NFs have a dedicated split between the requesting entity (the client) and the entity providing access to the resource requested (the server). What is REST? Client/Server Cacheable Request Stateless Client Server 3GPP NF Response 3GPP NF Layered System Uniform Interface Figure 3.5 - Client/server - REST in 5G NFs The client is called the service consumer and the server is called the service producer. Cacheable - a REST principle applicable to 5G The requested data from the server can be cached on the client, which reduces the number of transactions for frequently used data, hence improving the efficiency of the system. To enable caching, the payload received from the server can be implicitly or explicitly marked as cacheable or non-cacheable. Client/Server Cacheable Request Stateless Client Server 3GPP NF Response 3GPP NF Layered Data payload implicitly or explicitly labeled as cascheable or System non-casheable Uniform Interface Figure 3.6 - Cacheable property - REST in 5G NFs Building Blocks - Cloud Native Infrastructure Hence, a requesting client can store some information - for example, a user subscription - for further use, the client is notified when such information changes on the server, and the dirt