Description
A Network Slice Subnet Instance (NSSI) is a fundamental concept in the 3GPP network slicing architecture, representing an instantiated, managed, and operational segment of a network slice. While a Network Slice Instance (NSI) provides a complete, end-to-end logical network serving a particular business case, an NSSI constitutes a functional subset of that whole. An NSSI is a composition of managed physical and/or virtual resources, including Network Functions (NFs) and the necessary connectivity between them, that delivers a well-defined set of capabilities. Multiple NSSIs can be combined and interconnected to form a complete NSI. For example, an NSI for a factory automation service might be composed of separate NSSIs for the Radio Access Network (RAN) part, the Transport Network part, and the Core Network part, each with specific performance characteristics.
The management and orchestration of NSSIs are the responsibility of the Management and Orchestration (MANO) system, as defined in frameworks like ETSI NFV. The 3GPP Management System (3GPP MS) interacts with the MANO system to request the creation, modification, termination, and monitoring of NSSIs. Each NSSI has its own lifecycle, which is managed independently but coordinated to support the lifecycle of the parent NSI. An NSSI is described by a Network Slice Subnet Descriptor (NSSD), a template that defines the requirements and characteristics (e.g., capacity, latency, geographic area) of the subnet. The NSSD is used by the orchestrator to instantiate the corresponding NSSI with the appropriate resources.
From an operational perspective, NSSIs enable modularity, reuse, and efficient resource utilization in a sliced network. A single, high-performance transport NSSI might be shared as a common subnet across multiple different NSIs (e.g., one for eMBB and one for URLLC), provided the isolation and performance guarantees are met. This sharing is managed through the concept of nested slicing. The ability to manage subnets independently allows operators to scale, upgrade, or repair parts of a network slice without necessarily affecting the entire end-to-end service. Specifications such as TS 28.530 and TS 28.541 detail the management procedures and interfaces for NSSIs.
Purpose & Motivation
The concept of the NSSI was developed to address the practical complexity of deploying and managing end-to-end network slices. Creating a monolithic NSI from scratch for every new service would be highly inefficient and inflexible. The NSSI introduces a crucial layer of decomposition, allowing operators to build complex NSIs from smaller, reusable, and independently manageable building blocks.
This approach solves several key problems. First, it enables resource sharing and optimization across different slices. Instead of dedicating isolated resources for every function in every slice, common subnets (like a shared transport layer) can be created once and used by many slices, improving infrastructure efficiency. Second, it simplifies lifecycle management. Upgrading a core network function across dozens of slices can be achieved by updating a single, shared Core NSSI, rather than individually modifying each NSI. Third, it allows for different domains (RAN, Transport, Core) to be managed by different organizational units or even different vendors, with clear interfaces defined by the NSSI boundaries. The NSSI concept, therefore, is what makes large-scale, commercial network slicing operationally feasible and economically viable.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (131 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the NSSI function was introduced with new management use cases, including assigned priority and interactions with NFV MANO for network service priority. The release updated the procedures for NSSI provisioning with new operation names and enhanced the service profile in the network slice resource model to include availability. Additionally, it addressed modeling issues by updating the Information Service and Solution Set for Network Slice.
- 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
- Update operation names in the procedures of NSSI provisioning TS 28.531CR0003
- Replace symbol for network slice state management TS 28.541CR0027
- Update Information Service to fix Network Slice modeling issue TS 28.541CR0064
- Update Solution Set to fix Network Slice modeling issue TS 28.541CR0065
+ 1 more changes
In Release 16, key enhancements for the NSSI (Network Slice Subnet Instance) function included significant clarifications and corrections to the Network Slice NRM (Network Resource Model) and its related definitions. This release also introduced a decoupling between communication services and network slices and added transport information with slice mapping capabilities for backhaul endpoints. Furthermore, Release 16 provided stage 3 updates to solidify the model, specifically clarifying the relationship between GST, ServiceProfile, and SliceProfile datatypes.
- Add informative annex to describe a network slice journey TS 28.531CR0024
- Update on slice NRM TS 28.541CR0177
- Cleanup Network Slice related definitions in OAM space TS 28.530CR0025
- update slice NRM to align with refined slice definitions TS 28.530CR0027
- Replacement of instance of the term MF/managed function with network function TS 28.530CR0028
- Decouple communication service and network slice TS 28.530CR0033
+ 20 more changes
In Release 17, enhancements to the NSSI (Network Slice Subnet Instance) function introduced new procedures for reservation and feasibility checking of network slice subnets, and updated the allocation procedure for network slice subnet instances. The release also added explicit support for network slice subnet capabilities exposure and introduced a provider capability Information Object Class (IOC) for the subnet, alongside new slice optimization features based on VAL server policies.
- Modification of network slice related requirements TS 28.531CR0098
- Update procedure of reservation and checking feasibility of network slice subnet TS 28.531CR0106
- Update procedure of reservation and checking feasibility of network slice TS 28.531CR0107
- Update procedure of reservation and checking feasibility of network slice subnet TS 28.531CR0114
- Addition of attribute for network slice supporting maximum of data volume TS 28.541CR0366
- Update the information model definitions for network slice NRM TS 28.541CR0459
+ 34 more changes
In Release 18, key enhancements were made to the NSSI (Network Slice Subnet Instance) function by introducing support for asynchronous operations in its core lifecycle management procedures, specifically for allocation, deallocation, and modification. This release also added a new provisioning procedure for slice activation and deactivation using administrative state and introduced explicit configuration for UL and DL reliability within slice and subnet profiles. Furthermore, the specifications were updated to fix inconsistencies in SLA attributes and to enhance the support for network slice isolation.
- Add provisioning procedure for slice activation and deactivation using adminsitrative state TS 28.531CR0121
- Update Procedure of Network Slice Instance Allocation to support asynchronous operations TS 28.531CR0173
- Update Procedure of Network Slice Instance Deallocation to support asynchronous operations TS 28.531CR0174
- Update Procedure of Network Slice Instance Modification to support asynchronous operations TS 28.531CR0175
- Update Procedure of Network Slice Subnet Instance Allocation to support asynchronous operations TS 28.531CR0176
- Update Procedure of network slice subnet instance deallocation to support asynchronous operations TS 28.531CR0177
+ 39 more changes
In Release 19, the NSSI function was enhanced with new capabilities for predictive slice modification in edge deployments and inter-PLMN service continuity scenarios. It also introduced the incorporation of renewable energy percentage into slice deployment requests and added a late notification mechanism to the network slice adaptation procedures. Furthermore, the release brought enhancements to slice requirement verification, alignment, and the Network Slice as a Service (NSaaS) allocation model.
- 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
- Rel19 CR 28.541 Enhance the OpenAPI related to multiplicity for NrNrm and SliceNrm TS 28.541CR1406
- Rel19 CR TS28.541 Enhancing the isUnique property of stage 3 OpenAPI for NrNrm and SliceNrm TS 28.541CR1408
+ 7 more changes
Explore further
Broader topics and technologies where NSSI plays a role.
Defining Specifications
3GPP specifications that define or reference NSSI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.435 vj30 | Network Slice Capability Exposure Procedures | Rel-19 |
| TS 23.700 vk00 | XR Services Application Enablement Layer | Rel-20 |
| TR 26.941 vj01 | 5G Media Slicing Extensions | 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 28.536 vj20 | Management services for communication service assurance | 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 28.801 vf10 | Management and Orchestration of Network Slicing | Rel-15 |
| TR 28.808 vh00 | 5G satellite integration management study | 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 33.811 vf00 | Security study for 5G network slicing management | Rel-15 |