NTP packet size

[cak015]

What is the size of an NTP request packet and the size of an NTP response packet? I tried to look it up in the rfc1305 but it gave too many fields to nail it down.

Does anyone know?

[Ivan Ferreira]

You can use tcpdump to capture the packets going to port 123 to verify the packet size.

tcpdump -nXlf port 123

You can use ethereal also. Check the packet header.

[Bill Thorsteinson · Accepted solution]

I get a packet size of 90 to 97 bytes on my
network. Size may increase if you different
options.

Running ntpq gives me packets of various
sizes up to 474 bytes.

It looks like the minum packet size is 60
bytes, even if the internal data doesn't
require that much.

My current interval is 1024 seconds.
We send one packet and receive one packet
once each interval.

Overhead is far less than generated
by something like Microsoft file shares,
email clients etc.

[Steven E. Protter]

Shalom,

I think it can vary based on your linux distribution and what ntp package you use. There are actually options out there, and you can compile it yourself.

General network configuration may be an issue.

I don't think there is a standard, but you may be able to find out at http://www.npt.org

Good luck, and post what you find out.

Please

Thank You.

SEP