URSP Flow in a 5G Network

The User Plane Route Selection Policy (URSP) is a key feature in 5G networks, allowing devices to steer traffic to different data networks based on specific policies set by the network operator. URSP is part of Network Slicing in 5G and enables devices to utilize multiple PDU (Protocol Data Unit) sessions based on the type of application or traffic they generate.

This process ensures that the correct network resources are used for different types of services, optimizing performance and fulfilling Quality of Service (QoS) requirements for various applications. Below is a description of the URSP flow in a 5G network, along with a simplified diagram.

1. Policy Setup in the 5G Core

• The URSP policy is created by the network operator and stored in the Unified Data Management (UDM) and Policy Control Function (PCF) of the 5G core network.
• The URSP defines which traffic should be routed to which PDU session based on criteria like application ID, IP address, destination port, etc.

2. URSP Transmission to the Device

• When the User Equipment (UE) registers with the 5G network, the network provides the URSP policy to the UE. This happens through the Non-Access Stratum (NAS) signaling during the Registration Procedure.
• The policy is transmitted from the PCF to the AMF (Access and Mobility Management Function) and then to the UE.

3. Application on UE

• The UE applies the URSP policy locally and uses it to decide how to route its application traffic. Based on the rules, the UE determines which PDU session to use for each type of traffic.

4. PDU Session Establishment

• If a matching PDU session already exists, the UE uses it. If not, the UE requests to establish a new PDU session for the specific traffic flow.
• The UE initiates a PDU Session Establishment procedure with the 5G Core (AMF and SMF – Session Management Function).

5. Traffic Steering

• After the PDU session is established, the UE routes the application traffic according to the URSP rules. For example:
  • Application A (e.g., VoIP traffic) might use a PDU session with low-latency requirements.
  • Application B (e.g., internet browsing) might use a different PDU session with high throughput.

6. QoS Enforcement

• The network applies Quality of Service (QoS) parameters to the PDU sessions to ensure that the applications get the appropriate network resources. This includes setting priorities for bandwidth, latency, jitter, etc.

Use Cases of URSP in 5G

1. Network Slicing: Different applications (e.g., enhanced mobile broadband, ultra-reliable low-latency communications, massive machine-type communications) can be routed to different network slices, ensuring the right resources are allocated to meet their specific QoS requirements.
2. Traffic Management: Enterprise applications requiring high security, such as corporate email or database access, can be routed through private networks or encrypted tunnels, while regular internet traffic can be routed via public internet.
3. IoT Devices: IoT devices can have specific policies where critical sensor data is sent via low-latency, high-reliability PDU sessions, while less important data can use a different PDU session with lower priority.
4. Edge Computing: Traffic destined for local edge servers can be routed directly through a specific PDU session, while cloud-based traffic can use a different route.