OpenDaylight Project

The OpenDaylight controller is built around a modular, service-oriented architecture that separates the control plane from the data plane. At its core is the Model-Driven Service Abstraction Layer (MD-SAL), which provides a common framework for storing network state and exposing it via RESTCONF and other APIs. This design allows developers to write applications that interact with the network without being tied to specific vendor hardware or protocols.

Key components include the OpenFlow plugin for southbound communication, the Network Configuration Protocol (NETCONF) for device management, and a suite of network services such as topology discovery, forwarding rules, and virtual tenant networking. The platform also supports clustering for high availability and scalability, enabling it to manage large-scale deployments.

OpenDaylight was announced in April 2013 as a collaborative project under the Linux Foundation, with founding members including Cisco, IBM, and Microsoft. It was created to provide a common, open-source SDN controller that could accelerate innovation and avoid fragmentation in the emerging SDN market. The project has since released multiple major versions, each named after a chemical element (e.g., Hydrogen, Lithium, Sodium).

Governance is overseen by a technical steering committee and a board of directors, with contributions from a wide range of companies and individual developers. The project follows an open development model, with code hosted on GitHub and regular release cycles. Over time, it has evolved to incorporate new protocols and standards, such as OpenFlow 1.3 and YANG models.

OpenDaylight is used in a variety of scenarios, including data center automation, WAN optimization, and network slicing. It serves as the foundation for several commercial SDN products, such as Cisco's Open SDN Controller and Ericsson's SDN controller. Telecom operators and cloud providers have deployed it to manage virtualized network functions and to enable dynamic service chaining.

In research, OpenDaylight is a popular platform for experimenting with new network protocols and algorithms. Its modular architecture makes it easy to extend, and its support for multiple southbound protocols allows it to interoperate with a wide range of hardware. The project also provides a rich set of REST APIs, which are used by orchestration platforms like OpenStack and Kubernetes.

Beyond its mainstream use, OpenDaylight has several niche features and historical details. For instance, it includes a 'Network Intent Composition' (NIC) module that allows operators to specify high-level policies, which are then translated into low-level rules. Another lesser-known component is the 'Group Based Policy' (GBP) model, which provides an abstraction for policy-driven networking.

OpenDaylight also supports the 'OpenFlow Configuration and Management Protocol' (OF-CONFIG), which is used to manage OpenFlow switches. In terms of history, the project's early releases were sometimes criticized for being overly complex, leading to a refactoring effort in later versions. Additionally, OpenDaylight has been used in several academic studies on SDN performance and security, and it has a dedicated security working group that addresses vulnerabilities.

MD-SAL

Model-Driven Service Abstraction Layer, the core framework for data storage and API exposure.

OpenFlow

A communications protocol that gives access to the forwarding plane of a network switch.

NETCONF

Network Configuration Protocol, used for managing network devices.

RESTCONF

A RESTful protocol for accessing NETCONF data stores.

YANG

A data modeling language for network configuration and state.