Tech/Protocols/NTP
NTP Skew or Smear Sources
I promote redundancy at every chance. Having extra DNS servers or extra DHCP servers is always grand. One issue that I noticed recently was NTP Skew or Smear. This is a method of slowly adjusting the clocks on systems to compensate for leap seconds which happen from time to time. The process is well thought out and well documented however the implementation is not perfect. While discussing redundancy a network engineer was explaining the current solution and future plans. I was asked about the NTP setup and advised them to diversify vendors of hardware solutions. After a deeper dive I found they were using cloud provider vendor NTP services from a directive up the command chain. The issue came when I saw they were configuring multiple providers NTP servers as sources. The issue here is that NTP sources might use a different smear method and the inclusion of non-smeared sources would mean the NTP calculation would favor the lowest latency source as the various vendors smear drifted apart from atomic time.
Mixing algorithms is tricky https://developers.google.com/time/smear
NTP and GPS in the Datacentre
In new datacenter design the cable ingress egress is not really the stopper. Some areas (building codes) limit the number of antenna, or other exterior additions. I think the question needs to be asked, does your datacentre offer a NTP service in the building you can use? For example at HE you just use https://www.he.net/adm/ntp.html for your time and don't have to ask for an external antenna. My guess is that is not advertised.
Technical topics:
- Maximum run of antenna cable?
- Smart Hands access to roof?
- Lightning prevention and mitigation?
- With GPS outages how sure are you that it will help?