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Google Blogs About Plans to Use P4Runtime

April 09, 2018

Where hyperscale data center operators go, others follow. So, when Google announced this month that it will be using P4Runtime, it got people’s attention.

P4Runtime, the company explained, is the next step in the journey that started with software-defined networking adoption. And the Open Networking Foundation’s Stratum open source project will help bring P4Runtime to various network devices, Google Cloud added.

“P4Runtime allows the SDN control plane to establish a contract with the data plane about forwarding behavior, and to then establish forwarding behavior through simple RPCs,” Google Cloud’s Jim Wanderer and Amin Vahdat explained.

That will enable Google to leverage SDN solutions from various vendors that interoperate with its data centers and wide area networks to build higher performance and smarter networks. Google plans to take Stratum into production scale this year. However, the ONF told me last month that it considers Stratum to still be in the incubation phase.

In our interview, Timon Sloane of the ONF noted that SDN was originally about splitting the control and data planes. Now that’s come to pass, he added. In the meantime, the industry – and Google in particular – realized OpenFlow addresses only pipeline control. But it doesn’t address configuration, operations, and pipeline definition. To address these other challenges, more interfaces and protocols are required between the SDN switch and network operating system. So ONF defines them in Stratum.

Stratum employs P4Runtime for pipeline control. P4Runtime allows for faster modifications and one-time changes. (The Stratum Project also supports Broadcom’s SDKLT.)

The Project leverages gNMI with OpenConfig for configuration, and gNOI for operations. (Rebooting boxes is one of the things for which gNOI can be used.)

Additionally, the Stratum Project delivers a pipeline contract definition, which can be expressed in P4 or another language. And it can be updated at runtime on compatible systems.

As a result, Google and others will be able to define unambiguous contracts between the Network OS and the data plane. That means these interactions will be more explicit, less open to interpretation, and more deterministic – so there’s no question about different devices behaving differently in these scenarios.

Sloane says this is all about making sure you don't have to use backdoors or logins to manage the system. As a result, he adds, upgrade cycles are simplified, network operators can use white box systems with their choice of silicon, and the ecosystem can enjoy other benefits like faster time-to-market and reduced R&D. All that enables greater innovation, more availability and reliability, and much lower capex and opex, he says.

Twenty-four organizations are part of the Stratum Project. That includes major telcos China Unicom, NTT, and Turk Telekom/Netsia; cloud providers Google and Tencent; networking vendors Big Switch, Ruijie, and VMware; white box suppliers Dell EMC, Delta, Edgecore, and QCT; open source projects CORD, ONL, ONOS, OpenSwitch, OVS,, and SDKLT; and all the major silicon vendors. That group includes Barefoot, Broadcom, Cavium, Mellanox, and Xilinx.

Edited by Mandi Nowitz

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