ONF now looking northbound

A reversal? SDN organization forms working group to define controller-to-app API

The Open Networking Foundation, a user-driven organization defining and promoting OpenFlow-based software-defined networks, has established a working group to define a "northbound" API between SDN controllers and applications.

The ONF's Northbound Interface (NBI) Working Group is chartered to develop information models for NBIs, prototype them and gain end-user feedback on selected examples with "real code," according to the ONF's press release. The goal is to reduce end-user confusion on the northbound API - for which there are many options but no current standard -- and define an open API for application developers.

"The proliferation of approaches to NBIs is impeding the progress of SDN," said Dan Pitt, executive director of the Open Networking Foundation, in a statement. "As part of our role in helping the industry develop and maintain approaches to open SDN, we are taking the lead in helping end users better understand what NBIs serve what needs. The primary driver for our work in this area is the creation of one or a small number of stable, open interfaces that will support rapid adoption of SDN."

A parallel, vendor-driven group, OpenDaylight, is also defining a northbound API for SDNs. Catalyzed by Cisco and IBM, OpenDaylight was formed in April under the Linux Foundation to define an open source SDN "framework" that includes a controller.

[IN THE LOOP: OpenFlow and Cisco OPEN's feedback loop]

OpenDaylight says the ONF's NBI group represents a 180 degree turn by an organization that previously "dismissed" the need to work on a northbound API.

"We will monitor what is expected to be ongoing ONF discussions about the process for potentially creating a standard around the Northbound Interfaces sometime in the future" said Jim Zemlin, executive director of The Linux Foundation. "Right now OpenDaylight developers are focused on their first code release slated for December."

ONF, however, says it never dismissed the NBI and actually began its work last year -- before the debut of OpenDaylight -- as part of its Architecture and Framework Working Group's study of existing SDN NBI use cases and controller interfaces. Since that time, the number of northbound APIs has grown to more than 20, the organization says.

The volume has created confusion on which one(s) developers should write to, ONF says. And Pitt said earlier this year that ONF planned to comb through those 20 northbound APIs to narrow down the number - ideally, to one - developers need to write to.

"We continue to believe that software standards should be created by a committee only when absolutely necessary," states Pitt. "One of the purposes of the Working Group is to determine if an NBI standard from a committee is needed by the market. Over the last two years, we have said that more experience was needed with SDN controllers and applications before anyone could judge the qualities of a 'good' NBI. Our Working Group will build on the considerable body of experience gained since then and on the demand from application developers for assistance in understanding this critical component of a complete SDN solution."

ONF said back in April that it would be willing to collaborate with OpenDaylight in this effort and this week ONF Technical Programs Manager Rick Bauer reiterated the offer:

"ONF has initiated discussions with OpenDaylight, including the appointment of a formal liaison to their organization. If OpenDaylight publishes NBIs, ONF will include them in its evaluation of existing approaches to the northbound interface. If ONF produces useful information models for various latitudes and longitudes, we hope they will prove useful to OpenDaylight and its customers."

The ONF board will appoint a chairperson for the NBI Working Group in November, after applications are received from member company candidates. Initial information modeling will be completed in 2014.

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