Description
The Network Slice Selection Policy (NSSP) is a UE-local configuration that contains rules mapping application traffic to specific Network Slice Selection Assistance Information (S-NSSAI). It is a key enabler for device-driven slice selection, allowing the UE to intelligently request network slices that are optimal for its running applications without requiring explicit user intervention for each service. The NSSP is provided to the UE by the network, typically via the Unified Data Management (UDM) or Policy Control Function (PCF), and can be updated dynamically by the network operator.
An NSSP rule consists of several components: a traffic descriptor and a corresponding S-NSSAI. The traffic descriptor can be defined using various identifiers such as an Application Identifier (e.g., OSId + OSAppId), a Fully Qualified Domain Name (FQDN), or IP 3-tuple (destination IP address, protocol, port number). When an application on the UE generates traffic, the UE's operating system or modem software evaluates the NSSP rules. If the traffic matches a descriptor in an NSSP rule, the UE will include the associated S-NSSAI in its Requested NSSAI during registration or PDU Session Establishment procedures. This signals to the network (specifically to the NSSF and AMF) the UE's desire to use that particular network slice for the matched traffic.
The NSSP operates in conjunction with the UE Route Selection Policy (URSP), which is a broader policy that includes rules for traffic routing to specific Data Network Names (DNNs), SSC modes, and network slices. The NSSP can be considered a subset or a component focused specifically on slice selection. The presence of an NSSP allows for sophisticated use cases, such as a smartphone simultaneously using a default eMBB slice for general internet browsing while automatically requesting a low-latency slice for a cloud gaming application and a high-reliability slice for a mission-critical push-to-talk service, all based on pre-configured operator policies.
Purpose & Motivation
The NSSP was created to solve the problem of how a user device can intelligently and automatically select from multiple available network slices without relying on manual user configuration or simplistic network defaults. In early 5G deployments without NSSP, a UE might register with a single default slice for all its traffic, negating the benefits of having specialized slices. Alternatively, requiring users or application developers to manually select a slice for each app would be impractical and lead to a poor user experience.
The NSSP addresses this by putting policy intelligence directly in the UE, under the control of the network operator. This allows the operator to steer specific, identifiable application traffic to the slice that offers the most appropriate performance characteristics (e.g., low latency for gaming, high bandwidth for 4K video). It enables efficient network resource utilization by ensuring that premium slices are only used when needed by authorized applications. Furthermore, it future-proofs the device for new services; an operator can deploy a new slice for an emerging application (like AR glasses) and simply push a new NSSP rule to subscribed UEs to enable automatic use of that slice, without requiring a device OS update. The NSSP, therefore, is essential for realizing the user-facing benefits of network slicing in a scalable and automated manner.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (331 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the NSSP (Network Slice Selection Policy) function was introduced as part of the UE Policy Control Service, enabling the PCF to provision the UE with policies for network slice selection. These policies guide the UE in selecting appropriate network slices, identified by S-NSSAIs, based on operator configurations and application requirements. This mechanism supports the core 5G capability of providing tailored logical networks (Network Slices) for different service types.
- Architectural solution for User Plane (UP) Security policy and User Plane Integrity Protection TS 23.501CR0066
- Selection of NAS procedures for E-UTRA connected to both EPC and 5GC TS 23.501CR0147
- Paging Policy Differentiation correction TS 23.501CR0013
- Clarification on PCF selection TS 23.501CR0015
- Adding the new clause about SMSF selection TS 23.501CR0016
- Update Paging Policy Differentiation TS 23.501CR0036
+ 48 more changes
In Release 16, the NSSP (Network Slice Selection Policy) function was enhanced to support **Slice-Specific Authentication and Authorisation**, introducing the **NSSAAF** (Network Slice-specific Authentication and Authorization Function) and the concept of **Pending NSSAI** for pending authorization procedures. Furthermore, new capabilities were added for **Access Network Selection**, including specific procedures for **Trusted non-3GPP Access Network Selection** and selection for devices that **do not support NAS over WLAN**.
- CIoT Introduction of CN Selection and Steering TS 23.501CR0896
- ATSSS-SMF and UPF selection TS 23.501CR0761
- Trusted non-3GPP Access Network Selection TS 23.501CR0783
- eSBA communication schemas related to general discovery and selection TS 23.501CR0799
- eSBA communication schemas related to UDM and UDR discovery and selection TS 23.501CR0800
- Use of analytics for SMF selection TS 23.501CR0940
+ 73 more changes
In Release 17, the NSSP function was enhanced to support the selection of different network slices over different Non-3GPP accesses. Furthermore, new capabilities were introduced for Network Slice Admission Control, including support for Emergency and Priority Services and the enforcement of maximum throughput attributes per slice per UE.
- Support of different slices over different Non 3GPP access TS 23.501CR2525
- Network Slice restriction based on NWDAF analytics TS 23.501CR2567
- NWDAF discovery and selection TS 23.501CR2575
- NWDAF discovery and selection based on provided ML models TS 23.501CR2585
- UP path selection enhancement based on analytics info provided by NWDAF TS 23.501CR2586
- NWDAF discovery and selection for model sharing TS 23.501CR2614
+ 56 more changes
In Release 18, the Network Slice Selection Policy (NSSP) function was enhanced to support the change of Network Slice instance for an existing PDU session and to provide improved network control of UE behaviour for a network slice. It also introduced optimizations for time validity policies for a network slice and support for graceful termination of PDU sessions during network slice decommissioning or replacement.
- N3IWF selection enhancement for support of S-NSSAI needed by UE TS 23.501CR3707
- Discovery and Selection of the NWDAF Supporting Federated Learning in 5GC TS 23.501CR3772
- KI#4 23.501 AF traffic influence for common EAS, DNAI selection TS 23.501CR3788
- Common EAS/DNAI selection by AF TS 23.501CR3789
- Policy control enhancements to support multi-modal flows TS 23.501CR3864
- Change of Network Slice instance for PDU sessions TS 23.501CR3867
+ 82 more changes
In Release 19, the NSSP (Network Slice Selection Policy) function was enhanced with new capabilities for network function selection based on local offloading policies and target PLMN information. Specifically, the release introduced procedures for I-SMF selection/insertion based on a local offloading allowed indication and refined NF discovery and selection by the target PLMN. Additionally, support was added for UPF selection considering N6 delay and for slice change based on an AF request.
- RVAS with target NF selection enhancement. TS 23.501CR5364
- NF discovery and selection by target PLMN TS 23.501CR5399
- Support of UPF selection according to the conclusion in FS_UPEAS_Ph2 TS 23.501CR5441
- Local Offloading Policy provisioning TS 23.501CR5463
- Exposure enhancements for static UE IP address assignment and 5G VN group's User Plane Security Policy TS 23.501CR5492
- I-SMF selection/insertion based on local offloading allowed indication TS 23.501CR5604
+ 39 more changes
In Release 20, the NSSP (Network Slice Selection Policy) function was enhanced to support policy control for network energy saving, as indicated by the new architecture and exposure of energy consumption information. This update involved the EIF function to enable this policy control capability within the system. Additionally, the release introduced procedures for SMF and PCF selection to support the UIA_ARC.
Explore further
Broader topics and technologies where NSSP plays a role.
Defining Specifications
3GPP specifications that define or reference NSSP, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 24.890 vg00 | 5G NAS Protocol for 5GS Stage 3 | Rel-16 |
| TS 26.501 vj30 | 5G Media Streaming (5GMS) Architecture | Rel-19 |
| TR 26.941 vj01 | 5G Media Slicing Extensions | Rel-19 |