M-Plane architecture model in ORAN: Hierarchical and Hybrid Models

In the rapidly evolving world of Open Radio Access Networks (ORAN), efficient and robust management is paramount. The M-Plane, or Management Plane, plays a pivotal role in overseeing various functionalities within ORAN, including configuration, performance monitoring, fault handling, and software updates. This article delves into the core architecture models of the M-Plane, their characteristics, and the implications for ORAN deployment.

The Foundation: NETCONF/YANG

At the heart of the ORAN M-Plane lies the Network Configuration Protocol (NETCONF) and the YANG (Yet Another Next Generation) data modelling language. This standardized framework ensures seamless integration between different components, such as the Open Distributed Unit (O-DU) and Open Radio Unit (O-RU). It also facilitates the incorporation of diverse products with varying capabilities through well-defined data models. NETCONF's native support for multiple clients further bolsters the flexibility of the M-Plane architecture.

A significant advantage of the ORAN M-Plane architecture is its inherent flexibility. All O-RUs are designed to support both hierarchical and hybrid models, allowing operators to choose the model that best aligns with their operational requirements. Furthermore, the M-Plane specification mandates that all NETCONF servers support multiple sessions, ensuring that different management systems can concurrently interact with the O-RU.

Architectural Models: Hierarchical and Hybrid

The ORAN M-Plane offers two primary architectural models:

1. Hierarchical Model:

In this model, the O-RU is managed exclusively by one or more O-DUs using a NETCONF-based M-Plane interface. The O-DU acts as the central authority, orchestrating management operations for the O-RU. This model is suitable for scenarios where centralized management is preferred and where the O-DU is the primary interface for managing the O-RU.

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·???Centralized Management: In this model, the Open Distributed Unit (O-DU) takes on the central role in managing the Open Radio Unit (O-RU).

·???NETCONF Interface: The O-DU mgmt (management) entity uses the NETCONF protocol to communicate with and control the O-RU.

·???No Direct SMO Access: The Service Management and Orchestration (SMO) entity, responsible for higher-level network management functions, does not directly interact with the O-RU.

·???Limited Flexibility: This model offers less flexibility, as management of the O-RU is constrained by the capabilities of the O-DU.

2. Hybrid Model:

The hybrid model extends the capabilities of the hierarchical model by introducing direct logical interfaces between management systems (e.g., SMO – Service Management and Orchestration) and the O-RU. This enables granular management of specific O-RU functions, such as software updates, performance monitoring, configuration, and fault management, directly by specialized management systems. The O-DU still maintains a logical interface with the O-RU, primarily for forwarding packets between the O-RU and the management systems.

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·???Distributed Management: This model introduces direct logical interfaces between the SMO and the O-RU, alongside the existing O-DU-O-RU interface.

·???Multiple NETCONF Clients: Both the O-DU mgmt and the SMO can act as NETCONF clients, accessing the O-RU's NETCONF server.

·???Granular Control: The SMO gains direct control over certain O-RU management functions, allowing for more fine-grained and specialized management.

·???Increased Flexibility: This model offers greater flexibility, as the SMO can directly manage specific aspects of the O-RU.

Key Considerations in Hybrid Model:

·??Privilege Classes: NETCONF clients connecting to the O-RU in a hybrid model can have different privilege levels, allowing fine-grained control over access and management functions.

·??Multi-Operator O-RU: This scenario involves multiple O-DUs operated by different Shared Resource Operators. The M-Plane architecture models need to accommodate this shared resource management paradigm.

·??IP Connectivity: In the hybrid model, end-to-end IP connectivity between the O-RU and the management system (SMO) is established, either through the O-DU acting as a packet forwarder or through direct IP assignments.

Key points:

?? O-DU OAM (Operations, Administration, and Maintenance): The diagram highlights that O-DU OAM is outside the scope of this M-Plane discussion, focusing on O-RU management.

?? 1..N Relationships: The diagram indicates that there can be one or more (1..N) relationships between O-DU and O-RU entities, as well as between SMO and O-DU mgmt entities. This implies that multiple O-DUs can manage a single O-RU or vice-versa, and multiple SMOs can interact with different O-DUs.

?? Packet Forwarding: In the hybrid model, the O-DU can act as an IP/Ethernet packet forwarder, enabling communication between the SMO and the O-RU.

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The M-Plane architecture is a cornerstone of efficient and effective management in Open RAN deployments. By offering both hierarchical and hybrid models, ORAN provides operators with the flexibility to choose the optimal approach based on their specific needs. The use of NETCONF/YANG as the underlying framework further enhances interoperability and simplifies integration, making the M-Plane a crucial component in the ongoing evolution of open and disaggregated radio access networks.

M-Plane architecture model in ORAN: Hierarchical and Hybrid Models : https://techlteworld.com/m-plane-architecture-model-in-oran-hierarchical-and-hybrid-models/

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