Northbound Interface NBI
The software protocols and standards that are utilized between a Software Defined Networking (SDN) controller and the network management programs or scripts are known as a Northbound Interface (NBI) or Northbound API. In order to provide network programmability and quick automation, its main goal is to “open” the controller so that external programs can access its data and operations.
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Architectural Position
The NBI is positioned between the Application Plane (business logic, orchestration tools, security apps) and the Control Plane (SDN controller) in a network structure.
- Northbound: Attaches management systems and automation scripts “upwards” from the controller.
- Southbound: The Data Plane, which is made up of actual or virtual switches and routers, is connected “downwards” to the controller via Southbound interfaces.
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Key Characteristics and Functions
- Application-to-Control Plane: They provide as a link between the application layer, which is what users and apps view, and the control layer, which is the SDN controller.
- Network Abstraction: It simplifies complicated network operations into basic resources. By sending a single instruction to the NBI (e.g., “prioritize video traffic”), a developer can avoid developing code for dozens of different devices, and the controller will take care of the granular execution.
- Protocols and Implementation: The majority of contemporary NBIs are implemented using RESTful APIs (Representational State Transfer), which make use of HTTP/HTTPS communications, though there are other varieties as well. Applications that operate on the same server as the controller can also access native Java APIs from certain controllers, including the OpenDaylight (ODL) controller.
- Data Serialization: Data sent via an NBI is usually formatted in machine-readable, structured data languages such as XML (eXtensible Markup Language) or JSON (JavaScript Object Notation).
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Role in Network Automation
Network administration has changed since Northbound APIs were introduced, moving from manual, per-device configuration to automated, controller-based management.
- Model-Driven Data: NBIs deliver data based on codified data models, as opposed to traditional networks where engineers must interpret jumbled results from “show” instructions. A program can find certain network information considerably more easily as a result.
- Intent-Based Networking (IBN): An application can express “intent” through the NBI, such as stating that a particular user group should have access to a particular server. This is known as intent-based networking, or IBN. The required configurations are then determined and sent to the physical devices by the controller via its Southbound Interface (SBI).
- Advanced Applications: Assurance, which offers proactive monitoring and analytics, and Path Trace, which visualizes the path a packet traverses across a fabric, are examples of advanced applications made possible by NBIs.
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Examples in Cisco Architectures
- Cisco DNA Center: The main method by which users communicate with Software-Defined Access (SDA) networks, whether via a graphical user interface (GUI) or automation scripts, is via the Cisco DNA Center’s powerful northbound REST API.
- Cisco APIC: The Controller (APIC) exposes NBIs in the Application Centric Infrastructure (ACI) model for data centers, enabling orchestration and virtualization software to automatically set security rules and Endpoint Groups (EPGs).
- Cisco APIC-EM: Using a RESTful NBI, this enterprise controller enables programmatic control of conventional networking devices using apps like Plug & Play and Easy QoS.
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