ONOS, ONF Debut Leaf-Spine Design for Central Offices

The ONOS Project and Open Networking Foundation (ONF) have jointly unveiled a new leaf-spine design, or "fabric," that looks set to play a key role in the industry's Central Office Re-architected as a Data Center (CORD) open source initiative.

"The new fabric is the first Layer 2, Layer 3 leaf-spine built on bare metal and open source using an SDN control plane and more of an ASIC data plane," said Saurav Das, principal architect at the Open Networking Foundation. "We have overcome the challenges of SDN in the past in both the data plane and control plane."

By eliminating a number of distributed protocols, "classic" SDN was supposed to be the technology that disrupted legacy switch platforms from entrenched vendors, but that didn't happen.

"The problem with classic SDN was there were a lot of problems to overcome in the data plane and in the control plane that have progressed slowly over the years," Das said. "The problem was with the SDN stack (software) inside the switch not giving access to multiple features inside the switching ASIC. Without access to such features like multiple forwarding tables and port-groups for hashing and broadcast, an SDN solution could not be built that would scale to production-readiness.

"With our use of OpenFlow 1.3 and OF-DPA, an SDN controller finally has access to the features inside modern datacenter ASICs to develop solutions that scale in the data plane."

There are no distributed protocols on the SDN control plane in the new fabric and it's also more scaleable. The bare-metal switches cost a lot less and can tailor a network to applications.

While a leaf-spine fabric (where every "leaf" node connects to every spine node) is well-suited for any enterprise in which the underlay fabric plays a key role in the infrastructure, it's also significant for the CORD initiative.

CORD is designed to help network operators re-tool their central offices by bringing cloud-like agility and better economies of scale to their distributed locations.

"CORD as a whole is basically a solution for NFV using SDN and the cloud as its two fundamental principles," Das said. "CORD is being tried out by a number of vendors and carriers. They are essentially using the fabric and suggesting new features when they are using it as part of CORD."

Service providers that are working with ONOS include AT&T, China Unicom, NTT Communications Corp., SK Telecom Co. Ltd. and Verizon. (See Verizon Joins ONOS.)

AT&T has been using the CORD design in field trials during the first half of 2016, with production deployments expected later this year.

Vendors that have joined up with ONOS, which is a collaborative partner of The Linux Foundation, include Ciena, Cisco, Ericsson, Fujitsu Ltd., Huawei Technologies, Intel Corporation, NEC Corporation and Nokia.

The fabric was built on Edgecore Networks' bare-metal hardware from the Open Compute Project (OCP) and switch software, including OCP’s Open Network Linux and Broadcom’s OpenFlow Data Plane Abstraction (OF-DPA) API. The fabric taps into earlier work from ONF’s Atrium and SPRING-OPEN projects that used segment-routed networks with SDN.

Das said the fabric can work with many other bare-metal vendors.

"Because we use Open Network Linux (ONL) as the operating system, we can automatically use any bare-metal vendor certified/supported by ONL," he said.

Going forward, Ciena Blue Planet is adding test cases for build and deployment automation while Dell is working on support for more hardware.

"I think this is very important technology for different reasons," said Guru Parulkar, executive director of ON.Lab . "This is the first open source fabric that is based on bare metal and open source and SDN principles and that is a big deal.

"It's a very critical component of CORD and in that context it's getting actively used and going through proof of concepts and some field trials as well. I think, when you take all of these things together, it’s a really important platform and we expect the community and industry to use, build on and move forward with it."

— Mike Robuck, Editor, Telco Transformation