ONOS: The Game Changing SDN Controller?


ONOS (Open Network Operating System) is the first Open SDN Controller with focus on Service Provider Use Cases and their challenges of Scalability, High Availability & Performance. The support of Users and growing ecosystem, along with promising performance results make it a strong contender among SDN Controllers.

Software Defined Networking (SDN) has seen unprecedented hype and industry activity in the last three years.

“SDN is the next big thing in networking in decades, perhaps the next big thing after networking itself”.

Dan Pitt, ONF Executive Director

Indeed SDN brings a ray of hope for stagnating Telecom industry that might not have a sustainable business model with status quo in the future. As a result, several approaches to SDN have emerged each of its pros and cons. Among the available SDN Controllers, we have both vendor proprietary and open-source controllers. Vendor Specific controllers include VMware Nicira NSX, Cisco APIC, Alcatel-Lucent Nuage VSC, Brocade Vyatta, HP VAN and Cyan Blue Planet etc., while most notable open-source controllers are Open Daylight, Open Contrail, Big Switch Project Floodlight and Ryu etc. ONOS (Open Network Operating System) is the latest addition in the list of Open Source SDN Controller Projects. ONOS has been under development by ON.Lab (Open Networking Lab) since 2012 and was Open Sourced on Dec 5th 2014 after the support of AT&T and NTT in Nov 2014.

After having so many existing open-source controllers, one might wonder the need for another and why is it important?

To answer this, we have to look at the motivation behind open source projects and analyze various projects to see how they can deliver on the original SDN objectives of lower costs (both CAPEX & OPEX), faster TTM, Innovation, separation of control and forwarding and avoidance of vendor lock-in.

Open-source projects bring benefits such as Interoperability, Flexibility & Freedom from vendor lock-in, Customizability, reduced Costs and support from a large Community. There are three types of Open Source Ecosystems: Vendor Dominated, Loosely Aligned and Foundation Managed. The most effective and impactful projects tend to be Foundation Managed, e.g. OpenStack & Apache. The reason being a strong and independent community that is led by clear customer requirements, value proposition and transparency in rules of engagement among the members.

Majority of the existing SDN open-source initiatives are vendor dominated with inherent associated risks which could diminish the value of open-source, like vendor lock-in and business-model favoring the dominating vendor. In other words, such projects could be seen quite close to vendor proprietary solutions with the exception of added customization and interoperability.

One exception is OpenDaylight, which is a Linux Foundation project, supported by the largest community of vendors and has released its second code base Helium in March 2015. However, there has been skepticism over its intentions fueled by the fear that it was dominated by heavyweights like Cisco and IBM. ONF’s Dan Pitt also expressed his concerns that OpenDaylight seemed to have slowed down the SDN market innovation and it did not involve any users which was critical to understand and meet real user needs. ONF has also been critical of Cisco’s proposed OPFlex protocol which is now expected to emerge in OpenDaylight’s upcoming “Lithium” release.

In this context, ONOS has emerged as the first Open-Source SDN project focusing exclusively on service provider use cases and led by users including operators like AT&T, NTT, SK Telecom and ONF which has the support of software-oriented companies such as Google, Facebook, Yahoo, Verizon, and Microsoft. ONOS promised to address the challenges of Scalability, High Availability & Performance, all of which are critical for Carrier-Grade Networks.

“Software-defined networking can radically reshape the wide area network, the introduction of ONOS provides another open source SDN option designed for service provider networks with the potential to deliver the performance, scale, availability and core features that we value.”

John Donovan, SEVP, AT&T Technology & Operations.

While OpenDaylight has tried to accommodate several protocols in its southbound API layer, ONOS is focusing primarily on OpenFlow for new deployments and Netconf for legacy equipment. It also has Distributed (Clustered) Core which to provide scale-out and solve the problem of Open Flow controller scalability. It has a three month release cycle (more aggressive than ODL), the code for its second release, Blackbird, can be downloaded here.

ONOS Distributed Architecture

Given the support of large operators, vendors are rapidly joining the ecosystem and current list includes: Ericsson, Ciena, Cisco, Huawei, Intel, NEC and Fujitsu. Among them, Huawei has announced full support of ONOS in their SDN solution, while Ericsson terms ONOS as the cure for performance anxiety in SDN. Recently, ONOS has released performance metrics for its Blackbird release.

The numbers related to ONOS Blackbird performance metrics are impressive and promising.

In addition to performance, ONOS has several Service Provider Use Cases including Segment Routing, NFaaS, Multi-layer SDN and SDN-IP among others. It provides a vision of future network where POP and CO’s will be built like Data Centers and Core and Metro Packet Optical networks will be built on low cost hardware with separation of control and forwarding.

ONOS Service Provider Future Network


ONOS and OpenDaylight are the two most promising Open-Source SDN Controllers on the horizon but it’s still early days for both as yet. While ODL is arguably more mature and have a larger ecosystem (even though recently Juniper and VMWare reduced their commitments), ONOS has the increasing support of Operators and Use Cases which are customized for Operators’ requirements. Given the pace of rapid developments in the industry, it might take some time for a clear winner to emerge. The key to long-term success of either will be the adoption of real-world deployments in large-scale service provider networks.

Starting with a vendor-dominated/proprietary solutions can be a great tactical choice to understand technology, build internal capability and deploy current and immediate SDN Use Cases. However, given that SDN is going to be strategic to service provider’s core business, any SDN ecosystem should be evaluated to ensure vendor neutrality, large and non-vendor dominated base of developers & integrators and long-term viability (industry support) of the ecosystem.

Disclaimer: This article is an analysis on current and emerging state of SDN controllers and is not meant to cover a comprehensive list of SDN solutions/providers. The aim is to list examples to provide a clearer understanding but not to favor any company/vendor. All logos used in the article belong to their respective trademark owners.


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