What is the expected bandwidth for an NTP server?

I know that this question is answered in https://www.pool.ntp.org/join.html . However, I think this information is outdated. In that page it is said that most servers get about 5-15 NTP packets/sec, with spikes a couple of times a day of 60-120 packets/sec. This is roughly equivalent to 10-15Kbps with spikes of 50-120Kbps. In plain terms, you probably need at least 384-512Kbit bandwidth (in and out-going).

I have an NTP server in Italy with IPv6 connectivity. This server is advertised in the NTP pool project for more than a year. And it gets roughly 1 IPv6 NTP request per 5 seconds, or 0.2 packets/sec. So, the traffic is negligible.

Recently, I opened the same server to IPv4 network and advertised it in the NTP pool project for only a few days. The average packet request rate per second is now around 90-120 packets/sec. Together with the responses, it makes up a bandwidth of 11-15 KBytes/sec roughly. This translates to more than 100Kbps.

I cannot decide if this is normal or a coincidence (a “spike”). Does the documentation need an update?

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The numbers vary wildly depending on where in the world you are.

Is the 90-120 packets/second with the “384 kbps” setting, or did you update that recently? (I looked up your account).

For your question about the documentation: Yes, it should be updated. Suggestions are welcome and if the community here agrees then patches as well. (Including the dozen or so translations that need updating after we update the English version…)

FWIW, in the Italian zone the average rate of requests for the 1000mbit speed setting is currently about 2000 pps for IPv4 and 87 pps for IPv6.

I remember updating it just after adding my IPv4 server to the pool. Currently the server has on the average 5-12 KByte/sec inbound and similar (about 5-10 per cent smaller) outbound traffic. This is roughly last day’s traffic.

Now (just for testing) I increased the IPv6 Net Speed value to 1000Mbit and I will monitor to see if IPv6 traffic increases. IPv6 traffic is very small currently. Let’s wait and see if IPv6 traffic approaches 87 pps as mentioned by @mlichvar.

Totally, 1 GByte/day traffic is the maximum I can accept for my server. If I receive more than this, I may have to remove my IPv4 server from the pool. So, for the time being I leave the Net speed value for IPv4 to its lowest 384 Kbit.

Keep in mind too that 384k & 512k bandwidth settings give you only country/continent traffic, NOT any global traffic (You will notice on your account’s zones the (@) will dissappear.

When figuring bandwidth, a NTP packet is 48 bytes + 46 bytes for the Ethernet frame. So you end up with 94 bytes per query (in & out) for ‘actual’ traffic.


In Asia (and other underserved continents, probably) we serve thousands of packets per second even under least bandwidth setting. So it is generally impractical to run pool server without at least 3~5Mbps of upload line speed here.

I guess future translated version of join.html may include data to reflect statistic from zones speaking that language.

If the limitation is due to billing, your provider may or may not charge for the Ethernet frame bytes, though.

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In the dk pool i have 2 servers with 1000Mbit setting.
IPV4 server is just changed - so not mutch history here - but small increase, over the last 3 years - if i look on the historical data
IPV6 - have only been running a year increase from 10 to 47
1 IPV4 server Average 408.0 Datagrams/s http://www.ntp.567.dk/stat/rpi001_0system-udp.html
1 IPV6 server Average 47.0 Datagrams/s http://www.ntp.567.dk/stat/rpi-ipv6_0system-udp.html


Just an update:

IP4 @ 384 Kbit : Roughly 100 pps (~12 KB/s)
IP6 @ 1000 Mbit : Roughly 60 pps (~7 KB/s)

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Another update, after 2 weeks, for my server (with IPv4 and IPv6 connectivity) in Italy pool:

IP4 @ 1 Mbit : Roughly 330 pps (~41 KB/s)
IP6 @ 1000 Mbit : Roughly 60 pps (~7 KB/s)

Note: I changed IPv4 speed to 1 Mbit at MANAGE SERVERS.

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This is my last and final update, after changing IP4 speed to 1000 Mbit at MANAGE SERVERS and waiting 5 days:

IP4 @ 1000 Mbit : Roughly 1500 pps (~190 KB/s)
IP6 @ 1000 Mbit : Roughly 60 pps (~7 KB/s)


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Thanks for the updates :+1: