Np (application id: 16777342)

The Np interface facilitates communication between the Radio Access Network Congestion Awareness Function (RCAF) and the Policy and Charging Rules Function (PCRF). It plays a key role in handling congestion-related information and user equipment (UE) mobility within the network.
In the PCC architecture, the Np interface connects the RCAF with the PCRF.
Depending on the scenario:

• In a non-roaming scenario, the Np interface connects the RCAF to the home PCRF (H-PCRF).
• In a roaming scenario, the Np interface connects the RCAF to the visited PCRF (V-PCRF).

This architecture enables the RCAF to transmit congestion-related information and receive policy directives from the PCRF, ensuring that the network can dynamically adapt to changing conditions.

Np interface workflow

1. RUCI Reporting: The RCAF detects a congestion event in the RAN and sends a RUCI report to the PCRF via the Np interface.
2. Policy Decision: The PCRF evaluates the received RUCI information and makes a policy decision. This could involve adjusting QoS parameters, enforcing traffic management rules, or other actions aimed at alleviating congestion.
3. Response and Provisioning: The PCRF sends a response back to the RCAF, which may include policy directives or reporting restrictions. These instructions guide the RCAF in managing the congestion situation.
4. Session Termination: Once the exchange is complete, the session is terminated, ensuring that no state is maintained, which optimizes resource usage and system efficiency.

For complete technical specification of Np interface in Diameter protocol please refer to: [3GPP TS 29.217]