Description
The Network Service Virtual Link Identifier (NS-VLI) is a fundamental element within the 3GPP Network Resource Model (NRM) defined in TS 48.016. It serves as a unique key to identify a Network Service Virtual Link (NS-VL) object. An NS-VL represents a logical, virtualized communication link or connectivity service between two or more Network Functions (NFs) or endpoints within a managed network slice or service instance. The NS-VLI is not just a simple tag; it is a structured attribute that allows the network management system, such as the Network Slice Subnet Management Function (NSSMF) or the Network Slice Management Function (NSMF), to uniquely reference, configure, monitor, and modify the properties of this virtual link.
Architecturally, the NS-VLI is an attribute of the NS-VL Managed Object Class within the NRM's Information Object Class (IOC) hierarchy. This model is used by management interfaces, primarily the Itf-N interface, for communication between the Operation Support System (OSS) and the Network Management (NM) layer or between different NM layers. When a network slice or a complex network service is instantiated, the orchestrator creates various NS-VL objects to define the required connectivity topology between the virtualized network functions (VNFs) and physical network functions (PNFs). Each of these NS-VL objects is assigned a unique NS-VLI. This identifier is then used in all subsequent management operations, such as performance monitoring requests, fault management alerts, or configuration updates targeting that specific virtual link.
The role of the NS-VLI is central to automation and closed-loop operations. It enables management systems to correlate telemetry data, alarms, and configuration states with a specific logical link in a dynamic, software-defined environment. For example, when a performance threshold is crossed on a link carrying slice-specific traffic, the alarm generated will reference the NS-VLI, allowing the management system to pinpoint the affected slice's connectivity component instantly. Furthermore, in scenarios involving scaling or healing actions, the NS-VLI is used to identify which links need to be reconfigured or re-established as network functions are added, removed, or migrated. Its consistent use across the management fabric ensures that the logical service topology remains accurately mapped and controllable throughout its lifecycle.
Purpose & Motivation
The NS-VLI was introduced to address the management complexities arising from network virtualization and softwarization, particularly with the advent of Network Function Virtualization (NFV) and later, network slicing. In traditional, hardware-centric networks, physical links were identifiable by physical ports, cables, and circuit IDs. However, in a virtualized environment where multiple logical networks (slices) share the same physical infrastructure, there is a need to create, identify, and manage logical connections independently of the underlying physical topology. The NS-VLI provides this essential abstraction.
Prior to such identifiers, managing virtual connectivity was often ad-hoc, embedded within service-specific scripts, or tied directly to lower-layer identifiers like VLAN IDs or IP tunnels, which mixed service logic with transport details. This made service lifecycle management cumbersome, error-prone, and not scalable for automated, on-demand service provisioning. The creation of the NS-VLI as a standardized attribute within the 3GPP NRM provided a uniform, technology-agnostic way for management systems to refer to these virtual links. It decouples the service and slice management layer from the implementation details of the data plane connectivity, enabling a clear separation of concerns. This abstraction is a key enabler for the vision of agile service delivery and efficient resource utilization in 5G and beyond networks.
Key Features
- Unique identification of logical connectivity paths within a managed service or slice.
- Standardized attribute within the 3GPP Network Resource Model (TS 48.016).
- Enables automated lifecycle management (LCM) of virtual links.
- Facilitates correlation of faults, performance data, and configuration to specific service topology elements.
- Supports network slicing by providing slice-specific link identifiers.
- Used across management interfaces (e.g., Itf-N) for consistent reference.
Evolution Across Releases
Introduced as part of the initial definition of the Network Resource Model (NRM) for managing 3GPP networks. The NS-VLI was established as the key identifier for the Network Service Virtual Link Managed Object, providing a foundational construct for logical link management in evolving network architectures.
Defining Specifications
| Specification | Title |
|---|---|
| TS 48.016 | 3GPP TR 48.016 |