Having read the article now, I think what they missed was that a good NTP server implementation doesn’t depend on the commercial time servers that you can buy o

Having read the article now, I think what they missed was that a good NTP server implementation doesn’t depend on the commercial time servers that you can buy off the rack. They may have good GPS hardware and software, but many times their NTP implementation is … suboptimal. So, you instead get good GPS refclocks that give you a good direct PPS feed, which you then connect via serial port to your NTP time servers that will have a good implementation and configuration, because you’re making sure they do. And you make sure that you’ve also got some local-only refclocks in there to help ensure that you remain locked into a good frequency domain, even if you do lose visibility to the GPS network. This is typically a rubidium clock, although there are other options. You then synthesize the best information you can get from the GPS network as to what the exact time is at the moment you ask, with rubidium refclocks that can give you a very precise indication of exactly how long a second is, and you combine that with 40+ years worth of statistical knowledge and real-world experience through the NTPv3 protocol, and then you serve that time to your clients. Some vendors, like Meinberg, get all of this right, out of the box. But most don’t. Generally speaking, NTP easily handles single-digit millisecond resolution (with the right configuration and the right OS, even on pretty basic hardware), and can get down into the single-digit nanosecond range, but it gets harder and harder to push it into smaller and smaller time domains. The PTP protocol was created more recently, and they have a dependence on more modern hardware. PTP time sync won’t get off the local segment of the LAN, without support from the switches and other network hardware, whereas NTP is designed around basic UDP/IP networking and doesn’t place any requirements of this sort on the network. The requirement for hardware timestamping of network packets can cut both ways there, as can the requirement for using multicast. But PTP and NTP can be paired together for higher quality and higher resolution timekeeping than either protocol is capable of on their own. Then you get down to the trick of monitoring all that, so that you can prove what level of time sync you’ve got across your fleet of machines. That seems to be one of the real innovations here, but they don’t talk much about how they achieved that.