[time-nuts] Re: Network interface cards that support timestamping

[Ed Marciniak]

It’s too bad the SiT5721 is over $135 in 25 quantity orders. That prices it above a used but not used up rubidium.

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________________________________
From: Bill Notfaded via time-nuts <time-nuts at lists.febo.com>
Sent: Tuesday, January 31, 2023 5:21:04 AM
To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Cc: Bill Notfaded <notfaded1 at gmail.com>
Subject: [time-nuts] Re: Network interface cards that support timestamping

John-

I brought this up once before.  White Rabbit research has shown to do sync
well you need BIDI fiber SFPs.  Two wavelengths going opposite directions
down the same single mode fiber.  See:
https://ohwr.org/project/white-rabbit/wikis/SFP
The new future of nics that do this type of timing sync are DPU's.
https://www.nvidia.com/content/dam/en-zz/Solutions/gtcf21/networking/data-processing-unit/gtc-fall-21-networking-overall-dpu-technical-overview-firefly.pdf
I'm really interested in precision PTP over Ethernet over fiber.

Kinda related... Meta is looking at timebeat and I recently posted about
the new cards they're selling with MEMS DCOCXO SiT5721 for holdover.

https://engineering.fb.com/2022/11/21/production-engineering/precision-time-protocol-at-meta/#network

Seems the future of Ethernet timing sync time stamping is developing well
right now.  Fiber is the way to go though.

Bill

On Mon, Jan 30, 2023, 9:18 PM Lux, Jim via time-nuts <
time-nuts at lists.febo.com> wrote:

> On 1/30/23 5:31 PM, S McGrath via time-nuts wrote:
> > All your points are good ones,   My point was this is the common lowest
> > cost approach,  better approaches exist and they range from tens of
> dollars
> > to thousands depending on the accuracy needed.
> >
> > Driving the CD line with a ‘real’ serial port is good enough for
> ‘standard’
> > NTP timing applications,  its not good enough for a ‘time nuts’
> > implementation
>
>
> I daresay that finding a motherboard with a "real" serial port is pretty
> challenging. And even if you plugged in a serial expansion card of some
> sort, modern mobos probably aren't going to have a clean deterministic
> IRQ behavior.
>
> The idea of a (potentially inexpensive) standalone box that can do it is
> intriguing.  But we started with networking - So what is being discussed
> is something like a USB Ethernet dongle with time stamping.
>
>
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