Description
The Network Slice Instance Identifier (NSI ID) is a critical component of the 5G network slicing architecture, defined in the 5G System specifications. A Network Slice Instance is a real, instantiated logical network that provides specific network capabilities and characteristics. The NSI ID is the unique key used by management systems (specifically, the Network Slice Management Function (NSMF) and Communication Service Management Function (CSMF)) to identify, manage, and orchestrate a specific slice instance throughout its lifecycle—from creation and activation to modification, supervision, and decommissioning. The identifier is used within the management and orchestration (MANO) plane, as defined by 3GPP and often integrated with ETSI NFV MANO. It is referenced in network slice selection and subscription data, allowing the network to associate a UE with the correct slice. The NSI ID is distinct from the S-NSSAI (Single Network Slice Selection Assistance Information), which is used by the UE and the access network for slice selection during registration and session establishment. The S-NSSAI points to a Network Slice Type, and the network maps that request to a specific NSI using the NSI ID internally. The NSI ID binds together all the virtualized and physical resources—including core network functions (like AMF, SMF, UPF), RAN components, and transport network segments—that collectively realize the slice. Its uniqueness is paramount for ensuring strict isolation between slices, accurate charging, fault management, and performance monitoring per slice.
Purpose & Motivation
The NSI ID was introduced with 5G network slicing to solve the problem of managing multiple, isolated, logical networks running on a shared physical infrastructure. Pre-5G networks were largely monolithic, designed for a one-size-fits-all service model (primarily mobile broadband). The advent of diverse use cases—such as massive IoT, ultra-reliable low-latency communications (URLLC), and enhanced mobile broadband (eMBB)—required the ability to create tailored networks with specific performance, security, and functional characteristics. Network slicing is the architectural answer, but it necessitates a robust identification and management system. The NSI ID provides the fundamental handle for orchestration and lifecycle management. It addresses the limitation of not having a standardized, network-wide identifier to track a specific slice instance across all management domains (RAN, Transport, Core). This enables automated slice provisioning, granular resource allocation, independent operation and scaling of slices, and tenant-specific management, which are essential for 5G's vision of supporting vertical industries and new business models.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (401 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-14, normative work from Rel-15.
In Release 15, the NSI (Network Slice Instance) function was introduced as a new SUPI (Subscription Permanent Identifier) type, formally called the Network-Specific Identifier. This allowed the NSI to be used as a privacy-preserving identifier format within a SUCI, including support for an anonymous SUCI. The release also included clarifications and corrections for slice selection, subscription updates, and congestion control related to S-NSSAI.
- Add Network slice subnet management use case with assigned priority TS 28.531CR0009
- Add network slice management interactions with NFV MANO for network service priority TS 28.531CR0010
- Subscription identifier privacy suppport TS 31.102CR0778
- Correction to rejected S-NSSAI TS 23.501CR0007
- Use of identifiers for mobility between GERAN/UTRAN and 5GS TS 23.501CR0017
- Correction to handling of S-NSSAI mapping information TS 23.501CR0020
+ 61 more changes
In Release 16, the NSI (Network Slice Instance) function was enhanced to formally define the Network-Specific Identifier (NSI) as a new SUPI Type for use within a SUCI, enabling its use for privacy-preserving subscriber identification. This allowed for the creation of an anonymous SUCI by setting the SUPI Type to NSI and using the null protection scheme. Furthermore, the release introduced alignments and clarifications for network slice selection logic and interworking, including aspects related to CAG and NSSF interactions.
- Enhancement on slice interworking--501 TS 23.501CR0850
- Update the support of virtualized deployment with SCP distribution and the NF/NF service instance Set TS 23.501CR0926
- Introduction of Slice-Specific Authentication and Authorisation TS 23.501CR1174
- 23.501 part of PCF selection for PDU sessions with same DNN and S-NSSAI TS 23.501CR1375
- Add informative annex to describe a network slice journey TS 28.531CR0024
- Add radio resource utilization of network slice instance measurements TS 28.552CR0070
+ 71 more changes
In Release 17, the NSI (Network-Specific Identifier) function was enhanced to be formally usable as a SUPI type for generating an anonymous SUCI, as defined in the identifier structure. This allows for privacy-preserving subscriber identification where the scheme output corresponds to a username set to an "anonymous" string or an empty string, using the null protection scheme.
- Support of different slices over different Non 3GPP access TS 23.501CR2525
- Network Slice restriction based on NWDAF analytics TS 23.501CR2567
- TS23.501 KI#1 Network Slice Admission Control Function (NSACF) definition TS 23.501CR2679
- TS23.501 KI#2 Network Slice Admission Control Function (NSACF) definition TS 23.501CR2680
- Support for UE-Slice-MBR TS 23.501CR2706
- Support of 5GC assisted cell selection to access network slice TS 23.501CR2719
+ 73 more changes
In Release 18, the NSI (Network Slice Instance Identifier) function was enhanced to support network slice replacement for handover and to enable an asynchronous procedure for Network Slice Instance Allocation. Furthermore, new capabilities were introduced for the graceful termination of PDU sessions during slice decommissioning and for the provisioning of slice activation and deactivation using an administrative state.
- Slice-specific N3IWF FQDNs TS 23.003CR0647
- Support of TNGF selection based on the slices TS 23.003CR0670
- SNPN Identifier based N3IWF FQDN TS 23.003CR0687
- N3IWF selection enhancement for support of S-NSSAI needed by UE TS 23.501CR3707
- Change of Network Slice instance for PDU sessions TS 23.501CR3867
- Improved network control of the UE beahviour for a network slice TS 23.501CR3939
+ 113 more changes
In Release 19, the NSI (Network Slice Instance Identifier) function was enhanced to support slice requirement verification and alignment capabilities, as well as slice change procedures based on AF requests. The release also introduced support for exposing energy consumption information at the granularity of an S-NSSAI and incorporated renewable energy percentage considerations for slice deployment requests. Furthermore, enhancements were made to the network slice allocation procedure within the NSaaS model.
- Non-3GPP Device Identifier TS 23.003CR0708
- Definition of AIoT Device Permanent Identifier TS 23.003CR0713
- Enhancements to Network slice allocation procedure in NSaaS model TS 23.435CR0004
- Enhancements to Slice requirement verification and alignment capability TS 23.435CR0005
- Enhancements to Slice requirement verification and alignment capability TS 23.435CR0017
- Enhancements to Slice requirement verification and alignment capability TS 23.435CR0022
+ 53 more changes
Explore further
Broader topics and technologies where NSI plays a role.
Defining Specifications
3GPP specifications that define or reference NSI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.003 vj50 | Numbering, addressing and identification in 3GPP | Rel-19 |
| TS 23.435 vj30 | Network Slice Capability Exposure Procedures | Rel-19 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 23.799 ve00 | Study on Next Generation System Architecture | Rel-14 |
| TR 26.941 vj01 | 5G Media Slicing Extensions | Rel-19 |
| TS 28.202 vj00 | 5G Network Slice Management Charging | Rel-19 |
| TS 28.530 vj00 | Network Slicing Concepts & Requirements | Rel-19 |
| TS 28.531 vk00 | Management and Orchestration | Rel-20 |
| TS 28.535 vj00 | Closed Control Loop Assurance Management | Rel-19 |
| TS 28.541 vk00 | 5G Network Resource Model (NRM) Stage 2/3 | Rel-20 |
| TS 28.545 vh00 | Fault Supervision for 5G Networks | Rel-17 |
| TS 28.552 vk10 | 5G Performance Management Measurements | Rel-20 |
| TS 28.801 vf10 | Management and Orchestration of Network Slicing | Rel-15 |
| TS 28.805 vg10 | Management of Communication Services in 5G | Rel-16 |
| TR 28.808 vh00 | 5G satellite integration management study | Rel-17 |
| TR 28.812 vh10 | Study on Intent Driven Management Services | Rel-17 |
| TR 28.841 vi01 | Technical Report on IoT NTN Enhancements | Rel-18 |
| TS 28.861 vg00 | SON for 5G Networks Management | Rel-16 |
| TS 29.518 vj50 | AMF Service Based Interface Protocol | Rel-19 |
| TS 31.102 vj40 | USIM Application Specification | Rel-19 |
| TR 32.847 vi00 | Technical Report | Rel-18 |
| TS 32.899 vf10 | 5G Charging Architecture Study | Rel-15 |
| TS 33.117 vk00 | Catalogue of General Security Assurance Requirements | Rel-20 |
| TS 33.757 vj00 | Security for PLMN Hosting Non-Public Network | Rel-19 |
| TS 33.811 vf00 | Security study for 5G network slicing management | Rel-15 |