Sub Network Management Functions

Description

Sub Network Management Functions are a set of capabilities defined in 3GPP for managing a sub-network, which is a collection of network elements (NEs) that form a logical group, often based on technology, geography, or administrative boundaries. The functions are built around a network model that represents the sub-network, including the NEs and the relations (e.g., links, connections) between them. This model enables advanced management tasks that are not possible at the individual NE level, such as end-to-end service impact analysis and alarm correlation across multiple NEs.

The concept is part of the Telecommunications Management Network (TMN) framework and is specified in 3GPP TS 21.905 (Vocabulary for 3GPP Specifications). It aligns with ITU-T recommendations for network management, particularly the M.3000 series. The sub-network management layer sits between the Network Element Management Layer (NEML) and the Network Management Layer (NML) in the TMN hierarchy. It provides a consolidated view of a sub-network, allowing operators to manage it as a single entity for certain purposes.

Key functions include network topology presentation, which provides a graphical or logical view of the sub-network's elements and their connections; alarm correlation, which groups and filters alarms from multiple NEs to identify root causes; service impact analysis, which determines how failures or changes in the sub-network affect services; and circuit provisioning, which automates the setup and teardown of connections across the sub-network. These functions rely on the network model, which is typically stored in a management information base (MIB) or a similar database.

In 3GPP, sub-network management is relevant for both circuit-switched and packet-switched networks, and later for IMS and 5G. It is used by Element Management Systems (EMS) and Network Management Systems (NMS) to provide a hierarchical management view. For example, in a UMTS network, a sub-network might represent all NodeBs under a Radio Network Controller (RNC), or all RNCs in a region. The management functions allow the operator to monitor and control that sub-network as a unit.

The definition has remained stable since Release 4, indicating its foundational nature. As networks evolve toward virtualization and SDN/NFV, the concept of sub-network management is being adapted to manage virtualized network functions and slices, but the core principles of topology, correlation, and impact analysis remain. The term is part of the 3GPP vocabulary and is used across specifications that define management interfaces and procedures.

Purpose & Motivation

Sub Network Management Functions were created to address the need for managing groups of network elements in a coordinated way, rather than managing each element in isolation. In large networks, operators face thousands of NEs, and managing them individually is inefficient and error-prone. By defining a sub-network model, operators can perform tasks like alarm correlation, which reduces the number of alarms presented to operators by grouping related alarms and identifying the root cause. This improves operational efficiency and reduces mean time to repair (MTTR).

Service impact analysis is another key motivation: when a failure occurs, operators need to quickly understand which services are affected. A sub-network model allows the management system to trace the impact through the network topology, from the failed NE to the services that depend on it. Circuit provisioning benefits from a sub-network view because it can automate the configuration of multiple NEs to establish an end-to-end circuit, ensuring consistency and reducing manual errors.

The concept also supports hierarchical management, where higher-level management systems can delegate sub-network management to lower-level systems. This aligns with the TMN layered architecture and allows for scalable management. The definition has been stable because the fundamental needs of operators—topology awareness, alarm correlation, impact analysis, and provisioning—have not changed, even as technologies have evolved. The term remains relevant in modern networks, where sub-network management functions are implemented in orchestration and assurance systems.