AT&T is not happy with the lack of open source community involvement in the Contrail open source project. And the carrier is considering a "nirvana stack" for software-defined networking (SDN) that does not include Contrail.

AT&T’s integrated cloud (AIC) is based on the OpenStack framework, and it uses Juniper Networks' Contrail for its SDN. But at a session at the Open Networking Summit (ONS) last week, Paul Carver, a principle member of the technical staff with AT&T, expressed frustration with Contrail.

He said AT&T originally chose Contrail because it offered a wider variety of features than some of the other SDN controllers AT&T initially explored. “We wanted to take advantage of more features; that led us to Contrail,” said Carver. “Service function chaining was an area that Contrail had fully open-sourced.”

Juniper does the development of Contrail via open source toolsets. But Contrail has primarily been a Juniper project.

And that’s where Carver expressed dissatisfaction.

“The biggest challenge with Contrail is the lack of that community,” he said. “I personally have not given up yet to get more non-Juniper people working on it. But it’s been a real uphill battle. The key takeaway is: the communities are what’s most important to us.”

AT&T is eyeing a competing open source SDN controller: OpenDaylight (ODL).

Carver said ODL can configure virtual routers running inside a virtual machine (VM). It can configure optical hardware, and it can configure top-of-rack switches that provide the underlay fabric for its OpenStack cloud.

“Our Contrail-based OpenStack cloud runs on servers that are connected to top-of-rack switches that are manually configured,” he said.

Carver and his colleagues at AT&T have been envisioning what they call a “nirvana stack” for SDN built around open source. (see slide below).

“We think this is a promising set of open source communities,” he said. “This is what we’re looking at as a framework we would like to evolve from.”

AT&T’s AIC currently has about 80 zones with a roadmap for more than 100 by the end of 2017, with potentially hundreds more globally in the coming years.

“I have not completely given up on Contrail,” said Carver. “We would like Contrail to be a healthy open-source community. But this is where we see things going if that battle doesn’t pan out. If we can’t foster that community we need another one. I can’t make any commitments that this would replace Contrail in all AIC sites.”

Another AT&T slide from Carver's presentation shows the three primary open source SDN controllers: Contrail, ONOS, and ODL.

Huawei built its Agile SDN Controller based on ONOS, but it is also compatible with ODL via application program interfaces (APIs), according to Huawei officials when they announced the Agile Controller.

At last week’s ONS conference, Margaret Chiosi, vice president of Open Ecosystems with Huawei, said the company has created its Agile Controller, “taking what it sees as the best of breed from both projects.”

Pressed to elaborate more during the question and answer session after her speech, Chiosi said, “The real challenge is a healthy community of users and vendors working together.”

She said from her perspective, ON.Lab created the ONOS controller for greenfield environments where it could innovate freely. “The ODL side was focused more for brownfield,” she said. “It’s important to do greenfield and brownfield. Certain areas may need more convergence.”

Will one become more dominant than the other? “I don’t know,” she said. “From a vendor point of view, our goal is to take best of breed and keep working with these different organizations. My view is the community will decide. Whoever uses it is a testament to whether or not it’s still useful.”