Network Resource Model

Description

The Network Resource Model (NRM) is a cornerstone of the 3GPP Telecommunications Management Network (TMN) and Management System (MS) architecture. It is a comprehensive, object-oriented information model that provides an abstract representation of all physical and logical resources within a 3GPP network that are subject to management. The NRM is defined using Unified Modeling Language (UML) class diagrams and is implemented in management interfaces, typically using protocols like CORBA, SNMP, or more recently, NETCONF/YANG and RESTful APIs. Its primary function is to serve as the data schema for the Interface-N (Itf-N) reference point, which is used for communication between the Network Management (NM) layer and the Element Management (EM) layer or between different domains.

At its core, the NRM works by defining Managed Object (MO) classes. Each MO class represents a manageable network entity, such as a gNB, an AMF, a cell, a link, or a software feature. These classes have attributes that describe the entity's properties (e.g., administrative state, operational state, capacity parameters), notifications that the entity can emit (e.g., alarms, state changes), and actions that can be invoked upon it (e.g., reset, software upgrade). Crucially, the model also defines containment relationships (e.g., a gNB contains cells) and association relationships (e.g., a cell is associated with a frequency band) between these MO classes. This creates a hierarchical tree structure of managed objects that mirrors the network's physical and functional architecture.

Key components of the NRM are the Integration Reference Point (IRP) definitions. 3GPP defines multiple IRPs, each focusing on a specific management area: Configuration Management (CM), Fault Management (FM), Performance Management (PM), and Inventory Management (IM). Each IRP specifies a subset of the overall NRM, detailing the MO classes, attributes, and behaviors relevant to that management function. For example, the CM IRP defines MOs and attributes for configuring network elements, while the PM IRP defines MOs for collecting performance measurements like call drop rates or throughput. The NRM is extensible, allowing for the addition of new MO classes and attributes in each 3GPP release to support new network features, such as 5G NR, network slicing, or edge computing.

The role of the NRM in the network is to enable automated, standardized, and multi-vendor network management. By providing a common model, it ensures that a management system from one vendor can understand and control network elements from another vendor, as long as they both comply with the 3GPP NRM specifications. It is the foundation for provisioning new services, monitoring network health, collecting performance data for optimization, and maintaining an accurate inventory of network assets. The model's detail and structure allow for granular control and visibility, from high-level network slices down to individual hardware components within a base station.

Purpose & Motivation

The NRM was created to solve the critical problem of interoperability in managing complex, multi-vendor telecommunications networks. In the early days of mobile networks, each equipment vendor provided proprietary management interfaces and data models for their network elements. This forced operators to use separate, vendor-specific management systems, leading to operational inefficiency, high integration costs, and an inability to automate end-to-end service provisioning and assurance across the network.

The primary purpose of the NRM is to provide a standardized, technology-neutral information model that serves as a contract between network equipment providers and management system developers. It addresses the limitations of proprietary models by defining a common language for representing network resources. This allows for the development of generic, multi-vendor Network Management Systems (NMS) and Operations Support Systems (OSS) that can configure, monitor, and troubleshoot equipment from any compliant vendor. The motivation was deeply rooted in the TMN framework's goal of layered, standardized management.

Historically, its development began in 3GPP Release 4, formalizing management for UMTS networks. Its evolution has been driven by the introduction of new network architectures. Each new generation (3G, 4G, 5G) and new feature (IMS, LTE, NR, network slicing) necessitated extensions to the NRM to represent the new managed entities and their parameters. The NRM thus solves the ongoing challenge of keeping network management capabilities in lockstep with rapid network innovation, ensuring that operators can manage their entire heterogeneous network footprint through a consistent, standardized lens.

Key Features

• Object-oriented information model defining Managed Object (MO) classes for all network resources
• Structured using containment and association hierarchies to reflect network architecture
• Defined per Integration Reference Point (IRP) for Configuration, Fault, Performance, and Inventory Management
• Provides technology-neutral abstraction, applicable to 2G, 3G, 4G, and 5G network elements
• Enables multi-vendor interoperability for network management systems (NMS/OSS)
• Extensible model updated per 3GPP release to support new network features and architectures

Evolution Across Releases

Defining Specifications