Facebook Open Source Time Appliance for Data Center Networks

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Facebook engineers have built a time-based appliance for network synchronization and opened up the full specification, which should bring the price of the feature down significantly. The Open Compute project is based on a company-invented scorecard in a PCI Express (PCIe) form factor that can turn almost any basic server into a time appliance. With the help of the OCP community, he established the Open Compute Time Appliance project and opened all aspects of the Open Time Server.

Open Time Server Concept: The general idea is that the time card is connected via PCIe to the server and provides the time of day (TOD) through the / dev / ptpX interface. Using this interface, phc2sys continuously synchronizes PHC (PTP hardware clock) on the network card from the atomic clock on the time card. This provides an accuracy of

Time-based devices are essential parts of much of modern sync infrastructure, from 5G and automotive to financial services and TV broadcasting. All of these rely heavily on reliable distribution of time and frequency synchronization over packet networks. The big challenge with today’s off-the-shelf appliances is that while they work well and are tested and tested, they are often out of date, vulnerable to software security issues, and feature closed source software and proprietary hardware, which means they are makes it difficult to maintain. , repair and update; and they are also expensive.

By comparison, every aspect of the open compute time appliance design released today – including specifications, schematics, mechanics, BOM, and source code – is open source and available on the GitHub repository, under the name Open Parapluie of the calculation project.

Additionally, a Facebook spokesperson told EE Times that the new scorecard can be 10 times cheaper, three times more accurate and more compact than any commercial solution available today. He said the new scorecard could cost between $ 1,500 and $ 2,000, compared to the $ 50,000 range for current solutions.

Diagram of Facebook Time Device
System overview of the time device. The scorecard (light green block area) includes a GNSS receiver, atomic clock, and FPGA. The time card allows any x86 machine with NIC to be turned into a time device. (Source: Facebook)

The new time card allows any x86 machine with a network interface card (NIC) capable of hardware time stamping to be turned into a time appliance. This system is independent of whether it works for NTP, PTP, SyncE, or any other time synchronization protocol, as the accuracy and stability provided by the time card is sufficient for almost any system.

The scorecard built by Facebook consists of a GNSS receiver and a miniaturized atomic clock (MAC). This is important because it removes dependencies on internet connectivity and satellite signals which, if lost, could lead to outages or timing drift for dependent systems. With the built-in GNSS receiver and clock, users of the time device can keep the time accurate even if GNSS connectivity is lost. This is because the atomic clock turns on and can maintain accuracy for several hours until a signal is restored.

To implement the time engine in the time map, Facebook used an on-board MAC, a multiband GNSS receiver, and an FPGA. The job of the time engine is to interpolate in nanoseconds the required granularity between consecutive PPS (pulses per second) signals. The GNSS receiver also provides a ToD (time of day) in addition to a 1 PPS signal. In the event of loss of GNSS reception, the timing engine relies on the current synchronization of the atomic clock based on an average set of consecutive PPS pulses.

The time engine processing blocks on the FPGA include various filtering, timing, error checking, time stamping, and PCIe related subsystems to allow the time card to function as a system device that provides a specific time for the open time server.

Facebook scorecard
Facebook built its time card in a PCIe form factor, which can turn almost any basic server into a time appliance. (Source: Facebook)

Facebook said building a very accurate, inexpensive, vendor-free device without a vendor lock was a success in itself. Writing in an article on the development of the scorecard, the company’s network hardware engineers for the project, Ahmad Byagowi and Oleg Obleukhov, said, “We really wanted to make it free and make it open and affordable for everyone. , from a research scientist to a large cloud data center. That’s why we got involved with the Open Compute Project (OCP) to create a brand new Time Appliance Project (TAP). Under the umbrella of OCP, we opened the source code on the Time Appliance project’s GitHub repository, including specs, schematics, mechanics, BOM, and source code. Now, as long as printing the PCB and soldering tiny components doesn’t sound scary, anyone can make their own time card for a fraction of the cost of a regular time device. We have also worked with several vendors such as Orolia which will build and sell scorecards, and Nvidia which sells the ConnectX-6 Dx capable of precision timing (and the BlueField-2 DPU capable of precision timing).

They added: “We have published an Open Time Server specification on www.opentimeserver.com, which explains in detail how to combine the hardware (time card, network card, and convenience server) and software (operating system driver, NTP and / or PTP server) to build the time appliance. Building an appliance based on this specification will give full control to engineers responsible for maintaining the appliance, thereby improving monitoring, configuration, management and security.

For more details on the development of the open source scorecard, including a discussion of accuracy and source code, see the article on Embedded.com, “Open-sourcing a More Accurate Time Device.”

About Genevieve Swain

Genevieve Swain

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