4 ms·

I guess hardware-based techniques like 1588 and SyncE will come down in price in a few years. It seems natural that consumer-premises equipment will start offer

I guess hardware-based techniques like 1588 and SyncE will come down in price in a few years. It seems natural that consumer-premises equipment will start offering 1588 in, say, 2 years. Cheap 1588 can get you within 3ns, fancy switches can get you to within .3ns.

ebikelaw 8y ago
Won’t it be hard for 1588 hardware to compete on price with a pure software solution?
- nomel 8y ago
  1588 isn't just used for clock synchronization. A software solution will never allow you to know when a packet leaves/enters your network PHY, which enables some of it's other use cases.
  - ebikelaw 8y ago
    Hrmm yes a fair point. Also I see this paper suggests burning half a percent of your CPU resources for time synchronization which they wave away but I find to be quite substantial.
    - tinktank 8y ago
      > half a percent of your CPU resources for time synchronization Why do you find that to be substantial? Given most machines are at least 50% idle, I find 0.5% to be acceptable.
      - ebikelaw 8y ago
        It's actually quite difficult to get utilization up past about 60% on average at a large scale, and when utilization increases efficiency decreases (from missed clock turbo opportunities and other microarchitectural feedback). So if you are using half a percent of your nominal capacity that's 1% of your total CPU usage. 1% is a lot at scale. For example at Google's scale that would be enough to justify a team of several full-time engineers to find a more efficient way to do it. Even saving 0.01% of CPU time is considered a pretty good outcome at large companies (Amazon, Microsoft, Facebook, ...).
profquail 8y ago
Many (all?) Intel network adapters from the last decade have support for ieee1588; that includes embedded options like the i219-LM (and earlier models in that family): https://ark.intel.com/products/82185/Intel-Ethernet-Connection-I219-LM https://ark.intel.com/products/82185/Intel-Ethernet-Connecti...
- deleted 8y ago
  [deleted]
gsich 8y ago
ethtool -T eth0 will show if you have a PTP support for your NIC.

ebikelaw 8y ago

Won’t it be hard for 1588 hardware to compete on price with a pure software solution?

nomel 8y ago
1588 isn't just used for clock synchronization. A software solution will never allow you to know when a packet leaves/enters your network PHY, which enables some of it's other use cases.
- ebikelaw 8y ago
  Hrmm yes a fair point. Also I see this paper suggests burning half a percent of your CPU resources for time synchronization which they wave away but I find to be quite substantial.
  - tinktank 8y ago
    > half a percent of your CPU resources for time synchronization Why do you find that to be substantial? Given most machines are at least 50% idle, I find 0.5% to be acceptable.
    - ebikelaw 8y ago
      It's actually quite difficult to get utilization up past about 60% on average at a large scale, and when utilization increases efficiency decreases (from missed clock turbo opportunities and other microarchitectural feedback). So if you are using half a percent of your nominal capacity that's 1% of your total CPU usage. 1% is a lot at scale. For example at Google's scale that would be enough to justify a team of several full-time engineers to find a more efficient way to do it. Even saving 0.01% of CPU time is considered a pretty good outcome at large companies (Amazon, Microsoft, Facebook, ...).

profquail 8y ago

Many (all?) Intel network adapters from the last decade have support for ieee1588; that includes embedded options like the i219-LM (and earlier models in that family): https://ark.intel.com/products/82185/Intel-Ethernet-Connection-I219-LM https://ark.intel.com/products/82185/Intel-Ethernet-Connecti...

deleted 8y ago
[deleted]

gsich 8y ago

ethtool -T eth0 will show if you have a PTP support for your NIC.