Stratum Pool Servers

Is there a way to specify a certain stratum when using the NTP pool?
For example, if I wanted all pool members that are stratum 1, I could use or if I wanted stratum 2 servers, I could use


Hi DJX, welcome here in the community!

There is no way to select a Stratum 1 or Stratum 2 upstream pool member group, but chances are pretty high that the servers you connect with in the pool are Stratum 1 or Stratum 2. A 2018 research by the Ruhr-University in Buchum Germany found that at that moment 10% of the pool members were Stratum 1, and another 73.6% were Stratum 2. You can find this info in Table 3 in the PDF document I linked to.

Ok, thanks.
It would be a nice feature to have if anyone who can make this happen is reading.
So far, most of the hits I get off are stratum 3.

Yeah and that’s fine and desired.
If you wan’t only S1 server you can take a look here

The pool helps to reduce the load from the S1 and S2 server.
That you get S3 or even S4 server from the pool dosen’t mean that those aren worse then the upstream S1 & S2 server.

Hi, the deltas due to internet latency changing due to traffic level changes/routing changes etc are likely to be far greater than any delta caused by the stratum. The pool tries to find servers close to you to reduce that effect. The most important is to use the country pools closest to you. There’s a list you can drill down here:

ntpd documentation does not recommend use servers from Stratum1 list directly. Only if you will be stratum-2 server for many-many clients (like pool member). If you just customer it’s recommended to use Stratum2 servers

Really pool servers is good. Pool monitor them and kick off bad servers.

Also anyone can buld own stratum1 server with GPS/GNSS reciever. Chinese uBlox 6/7 “gnss RS232” recievers costs $15 and work ok. (ublox7 can work with GPS+GLONASS at the same time. uBlox6 only GPS or GLONASS). Chinese NTP servers on GNSS+microcontroller with Ethernet costs $100 on eBay (I think it cannot run in highload like pool, but will be good for LAN and as personal use). Even on windowsill GPS will recieve up to 10 satellites and work well (you can do simply 5-minutes test on windowsill with GPStest on smartphone). There are many articles in internet.

It’s amusing (and or confusing…) when people jump through hoops to research how the system works rather than just looking at the code (or for this sort of thing asking!).

The current breakdown by stratum is below.

I haven’t looked recently, but as others have said a lower stratum number isn’t a meaningful indication the server will return better time. A “stratum 1” server takes more care and feeding than one that uses multiple other servers to set the time. For example during leap second events among the servers that get the leap second wrong, the stratum 2 (or above) systems have in the past recovered much faster than some of the stratum 1 servers that needed human intervention.

stratum percent
1 12.5544
2 68.4078
3 17.2738
4 1.5808
5 0.0687
6 0.1145
select count(*) into @c from servers 
 where score_raw > 10 and deletion_on is null and stratum > 0;
select stratum, (100/@c)*count(*) as percent from servers
  where score_raw > 10 and deletion_on is null and stratum > 0 group by 1;
1 Like