3 ms·

Just wanted to note: the entire configuration I'm building out is automated to run on any Debian/Ubuntu OS (not just a Pi), and my intent is to make NTP + PTP s

Just wanted to note: the entire configuration I'm building out is automated to run on any Debian/Ubuntu OS (not just a Pi), and my intent is to make NTP + PTP setup much more approachable for those who want to tinker with it. The project is on GitHub: https://github.com/geerlingguy/time-pi https://github.com/geerlingguy/time-pi The blog post has more color/story around it, but the meat of it is over on GitHub, and right now I'm working my way through testing different network switches, installing an external GPS antenna, etc. Also, if you're a PTP nerd, you might want to check out a project from the OCP-TAP, the Switchberry, an open hardware design for a PTP boundary/transparent clock with 7 ports! [1] This was built by the same PCB designers as the TimeHAT featured in my blog post, and I'm trying to hammer out some bugs in the bringup so they can be nice, lower-cost options for networks where you don't have the budget or need for enterprise-level PTP offerings, but still want a decent DIY setup. [1] https://github.com/Time-Appliances-Project/Incubation-Projects/tree/master/Hardware/Switchberry_V1 https://github.com/Time-Appliances-Project/Incubation-Projec...

owenfi 2y ago
Sorry if the article or references answered this but I couldn’t quite tell if so: What are the bandwidth requirements of establishing clock sync around 1ms?
- michaelt 2y ago
  The bandwidth requirements are very low - you can sync time over a 56kbps serial port if you like. However, the big benefit of PTP is having your precise timing and your main network connection share a single wire - so if your server needs 10 Gbps for whatever the server does, to get the highest accuracy you'd want a PTP compatible switch with 10Gbps ports.
- wcunning 2y ago
  The bandwidth is low, but the latency requirements are stringent since PTP does a wire delay calculation with multiple back-and-forth messages. If that gets affected by, for instance, jumbo frames being on, your bound on the clock value is much worse than if you have a relatively uncongested link.

owenfi 2y ago

Sorry if the article or references answered this but I couldn’t quite tell if so: What are the bandwidth requirements of establishing clock sync around 1ms?

michaelt 2y ago
The bandwidth requirements are very low - you can sync time over a 56kbps serial port if you like. However, the big benefit of PTP is having your precise timing and your main network connection share a single wire - so if your server needs 10 Gbps for whatever the server does, to get the highest accuracy you'd want a PTP compatible switch with 10Gbps ports.
wcunning 2y ago
The bandwidth is low, but the latency requirements are stringent since PTP does a wire delay calculation with multiple back-and-forth messages. If that gets affected by, for instance, jumbo frames being on, your bound on the clock value is much worse than if you have a relatively uncongested link.