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ONF Debuts Open Source 'Stratum' Switch OS

Stephen Lawson
News Analysis
Stephen Lawson
9/10/2019

The Open Networking Foundation made a major advance in its next-generation SDN initiative on Tuesday, releasing its Stratum switch operating system as open source.

Stratum is a silicon-independent platform designed to let network operators easily integrate new devices from a wide range of vendors, expanding and upgrading their infrastructure in real time. It strictly defines the interface between switches and controllers as an unambiguous "contract," avoiding proprietary silicon interfaces and software APIs that lock operators into one vendor's hardware.

Starting Tuesday, Stratum is freely available under the Apache 2.0 license. This should lead to wider adoption and a broader ecosystem, accelerating the software from current lab testing to field trials within 12 months, ONF said.

The software is intended to support both fixed-function and programmable switch chips. It already works with the Tofino programmable silicon architecture from startup Barefoot Networks, which recently was acquired by Intel, and Broadcom's Tomahawk chip family, Timon Sloane, ONF's vice president of standards and membership, tells Light Reading. It can run on white-box switches from Dell Technologies, Delta Networks, Edgecore Networks, Inventec, QCT and Stordis.


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Stratum is a big step forward for the ONF, which last year began to focus more closely on the needs of operators that wanted freedom from vendor lock-in. The older OpenFlow specification provides guidelines for open interfaces among software-defined network elements, but in many cases was used as the basis for proprietary switches and chips instead of truly open platforms, Sloane says.

The OS uses an interface based on the P4 open-source programming language to define a strict relationship between a switch and its controller. This allows operators to mix and match hardware from a range of vendors, including switches based on different silicon, without having to modify the controller or even retest or re-validate the network, the ONF says.

Stratum also exposes a set of SDN interfaces including P4Runtime, OpenConfig, gNMI and gNOI, allowing programmability of control, configuration and operations for full lifecycle management. It can work with either an external network OS in an SDN architecture or network OS functions running locally on the switch.

Stratum will be a "substrate" within the ONF's next-generation SDN stack, designed to complement projects including the Trellis data-center switching fabric, the CORD carrier service-delivery platform and the ONOS SDN controller, Sloane said. "By slipping in Stratum, you get a whole new set of capabilities," he said.

The project began in March 2018 with seed code from Google. Stratum has been incubating since then, with several organizations collaborating to make it compatible with silicon from multiple vendors and easier to consume as open source.

The ONF intends Stratum as a production-ready distribution for white-box switches. Current lab trials are exploring Stratum by itself. Within six months, development will probably expand to lab trials as part of broader ONF platforms, the ONF says. The group expects field trials of Stratum-based systems within 12 months. Google has committed to using elements of the platform in production.

Last March, the ONF had forecast the release of Stratum for early this year.

"Sometimes these things take longer than you expect," Sloane said. "We didn't want to release it until multiple silicon from multiple vendors was supported."

Operators backing the project include China Unicom, Turk Telekom, Japan's NTT Group and Netherlands-based KPN.

Why this matters
For network operators to fully take advantage of open networking for flexibility and cost-cutting, they need to be able to choose from a range of easily programmable hardware. The ONF's Stratum project offers a strictly defined switch OS that, if widely adopted, could let operators easily mix and match switches from different vendors based on any supported silicon platform. Combined with higher-level platforms in the ONF's open networking stack, Stratum could go a long way toward freeing operators from the limitations of proprietary systems.

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— Stephen Lawson, special to Light Reading. Follow him on Twitter [@sdlawsonmedia]

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