Control Plane Network Function Architecture
CP NFs are designed around a three-tiered architecture that take advantage of the stateful/stateless capabilities afforded within cloud native environments.
The architectural tiers are as follows:
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Protocol Load Balancer Services — These are stateless microservices that are primarily responsible for dynamic discovery of application containers as well as for protocol proxy and/or termination. These include traditional 3GPP protocols and new protocols introduced with 5G.
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Applications Services — Responsible for implementing the core application/business logic, these are the stateless services that render the actual application based on the received information. This layer may contain varying degrees of microservice granularity. Application services are stateless.
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State management services — Enable stateless application services by providing a common data layer (CDL) to store/cache state information (e.g. session and subscriber data). This layer supports various data storage technologies from in-memory caches to full-fledge databases.

The three-tiered architecture on which Cisco's CP NFs are designed full support the 5G core (5GC) Service-based Architecture (SBA) defined by 3GPP. These NFs communicate with each other and with third-party NFs over the Service-based Interface (SBI) using HTTP/2 over TCP as defined by 3GPP.

Refer to the Overview Chapter for more information on the respective Cisco NF.