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AT&T trials open switches for better future services

Stephen Lawson | April 5, 2017
The carrier took a programmable chip from foundry to network in less than three months


A coast-to-coast network trial by AT&T last month, using open-source "white box" switches, pointed toward an imagined future of more reliable services that may come quicker than some people think.

The carrier ran a trial on its core network earlier this year using switches based on chips from Intel, Broadcom and startup Barefoot Networks. The latter only started shipping in sample quantities in December, making the trial deployment a remarkably quick turnaround.

Like other carriers and cloud providers, AT&T is aggressively shifting its network toward SDN (software-defined networking). As these changes are carried out across more infrastructure, they should give both service providers and subscribers more flexibility and higher performance.

AT&T called its trial the first of its kind in the telecommunications industry. It set up white-box switches from two different manufacturers, using processors from the three merchant-silicon vendors, and ran an open network OS from SnapRoute on all three. The trial involved carrying customer traffic across the U.S. on the carrier's core network.

All three chip companies sell networking processors that are available to any manufacturer, helping less established vendors better compete with big names like Cisco Systems that design some of their own chips.

Barefoot's Tofino chip stands out because of its capabilities and the fact that it's so new. Announced last June, the Tofino is designed to be more highly programmable than conventional switching silicon. It also promises high performance, going through packets at 6.5Tbps (bits per second).

After the processor started sampling in December, AT&T started working with Barefoot and white-box manufacturer Edgecore Networks. (Switch builder Agema Systems also participated in the trial.) Less than three months later, they had a switch based on Facebook's Wedge 100 design that not only did standard routing but also was programmed for new packet-processing functions. Those capabilities provide real-time information about the state of every packet on the network, said Andre Fuetsch, chief technology officer and president of AT&T Labs.

He compared this new visibility to the move from X-ray to MRI (magnetic resonance imagery) in medicine. It will open up new capabilities the same way adding GPS to phones did, Fuetsch said. This will help AT&T deliver 5G wireless features including high speed and low latency, he said.

Though SDN and network functions virtualization have shifted many network functions onto standard x86 servers, tasks like packet-by-packet inspection have to happen inside a switch to keep up with the kind of performance a Tofino-based switch delivers, said Ed Doe, Barefoot's vice president, product and business. Programmability allows customers to bring those functions into the processor.

The speed with which AT&T put Barefoot's new switch chip into a trial surprised IHS Markit analyst Michael Howard, a longtime observer of network technologies. For subscribers, the kind of visibility that AT&T achieved could mean higher performance and more dependable service-level agreements, because the network will be able to constantly gauge what resources are required and make them available, he said.


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