ONOS SDN Controller Review: Architecture & Use Cases 2025
The Open Network Operating System (ONOS) consistently ranks as the top-rated open-source SDN controller for Communication Service Provider networks. With a score of 92% in our comprehensive evaluation, ONOS excels in API extensibility, production-ready scalability, and the unique ability to support transitions from legacy “brown field” networks to SDN “green field” deployments.
This is part of our comprehensive SDN Controller Comparison Guide, where we evaluate 6 leading open-source controllers across 13 technical criteria.
ONOS at a Glance
| Attribute | Details |
|---|---|
| Overall Score | 92.0% (Ranked #1) |
| Best For | Communication Service Providers, SD-WAN, Enterprise networks |
| Architecture | Distributed, three-tier |
| Programming Language | Java |
| Primary Protocols | OpenFlow, P4, NETCONF, BGP, PCEP, SNMP, TL1, RESTCONF |
| Clustering | Native (Atomix datastore) |
| Community | Linux Foundation Networking |
| Key Differentiator | Only SDN controller supporting brown field to green field transition |
| Deployment Complexity | Moderate |
| License | Apache 2.0 |
What ONOS Does Best:
- Extensive southbound and northbound API support
- Intent-based networking framework
- Production-grade horizontal scalability
- Geographic redundancy for SD-WANs
- Native BGP routing for multi-site coordination
Architecture Deep Dive
ONOS is designed as a three-tier architecture as follows:
Modularity and Extensibility
ONOS has built-in mechanisms for connecting/disconnecting components while the controller is running. This allows a very flexible approach to adding functionality to the controller.
Scalability
ONOS is designed specifically to horizontally scale for performance and geo-redundancy across small regions.
Telemetry
Telemetry feeds are available through pluggable modules that come with the software, with Influx DB and Grafana plug-ins included in the latest release.
Resilience and Fault Tolerance
ONOS has a very simple administration mechanism for clusters with native commands for adding and removing members.
The Open Network Operating System provides fault tolerance in the system with an odd number of SDN controllers. In the event of Master node failure, a new leader would be selected to take the control of the network.
Programming Language
ONOS is written in Java.
Community
The Open Network Operating System is supported under the Linux Foundation Networking umbrella and boasts a large developer and user community.
Conclusion
Given this evaluation, the Open Network Operating System is a suitable choice for Communication Service Providers (CSP). This is because ONOS supports an extensive list of northbound and southbound APIs so vendors do not have to write their own protocol to configure their devices. It also supports the YANG model which enables vendors to write their applications against this model. The scalability of ONOS make it highly available and resilient against failure which increases the customer user experience. Finally, the software modularity features of ONOS allows users to easily customise, read, test and maintain.
Next, we will be evaluating OpenDayLight.
