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Comparison of Software Defined Networking (SDN) Controllers. Part 3: OpenDayLight (ODL)

By 25/07/2019 November 27th, 2019 No Comments
Aptira Comparison of Software Defined Networking (SDN) Controllers. OpenDayLight ODL

Our Open Source Software Defined Networking (SDN) Controller comparison continues with OpenDayLight (ODL). ODL is more focused on the SD-LAN and Cloud integration spaces.

OpenDaylight is a modular open platform for customising and automating networks of any size and scale. The OpenDaylight Project arose out of the SDN movement, with a clear focus on network programmability. It was designed from the outset as a foundation for commercial solutions that address a variety of use cases in existing network environments.

Architecture

ODL consists of 3 layers:

Aptira Comparison of Software Defined Networking (SDN) Controllers. OpenDayLight ODL Diagram
  • Southbound plugins to communicate with the network devices
  • Core Services that can be used by means of Service Abstraction Layer (SAL) which is based on OSGi to help components going in and out of the controller while the controller is running
  • Northbound interfaces (e.g. REST/NETCONF) that allow operators to apply high-level policies to network devices or integration of ODL with other platforms

Modularity and Extensibility

Built-in mechanisms provided by ODL simplify the connection of code modules. The controller takes advantage of OSGi containers for loading bundles at runtime, allowing a very flexible approach to adding functionality.

Scalability

ODL uses a model-based approach, which implies a global, in-memory view of the network is required to perform logic calculations. ODL’s latest release further advances the platform’s scalability and robustness, with new capabilities supporting multi-site deployments for geographic reach, application performance and fault tolerance.

Cluster Scalability

  • ODL contains internal functionality for maintaining a cluster, AKKA as a distributed datastore shares the current SDN state and allows for controllers to failover in the event of a cluster partition
  • As a cluster grows however, communication and coordination activities rapidly increase, limiting performance gains per additional cluster member

Architectural Scalability

  • ODL includes native BGP routing capabilities to coordinate traffic flows between the SDN islands
  • Introduction of OpenDaylight into OpenStack provided multi-site networking while boosts networking performance

Interfaces

  • Southbound: It supports an extensive list of Southbound interfaces including OpenFlow, P4, NETCONF, SNMP, BGP, RESTCONF and PCEP.
  • Northbound: ODL offers the largest set of northbound interfaces with gRPC and RESTful APIs. The northbound interfaces supported by ODL include OSGi for applications in the same address space as the controller and the standard RESTful interface. DLUX is used to represent Northbound interfaces visually to ease integration and development work.

Telemetry

At a project level, ODL has limited telemetry related functionality. With the latest development release, there are moves toward providing northbound telemetry feeds, but they are in early design and not likely to be ready for production in the short term.

Resilience and Fault Tolerance

ODL fault tolerance mechanism is similar to ONOS, with an odd number of SDN controllers required to provide fault tolerance in the system. In the event of master node failure, a new leader would be selected to take the control of the network. The mechanism of choosing a leader is slightly different in these controllers – while ONOS focuses on eventually consistent, ODL focuses on high availability.

Programming Language

From a language perspective, ODL is written in Java.

Community

ODL is the second of the SDN controllers under the Linux Foundation Networking umbrella. This project has the largest community support of all open source SDN controllers in the market, with several big-name companies actively involved with development.

Conclusion

OpenDayLight is the most pervasive open-source SDN controller with extensive northbound and southbound APIs. In addition to resiliency and scalability, the modular architecture of ODL makes it a suitable choice for different use-cases. This is why OpenDayLight has been integrated into other open-source SDN/NFV orchestration and management solutions such as OpenStack, Kubernetes, OPNFV and ONAP which are very popular platforms in telco environments.
Next, we will be evaluating OpenKilda.

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