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I noticed that there is a timestamp option -T in the ping help. But I don't know how to use it.

I tried:

ping -T

This is what I get:

Invalid timestamp type

What is the timestamp type and how do I use it?

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up vote 9 down vote accepted

The -T option is used to ask hops to insert the timestamp in the IP packets upon receiving the ping. It works by using the TS option of IP packets, specified by RFC791.

ping -T requires an argument: one of tsonly, tsandaddr or tsprespec. You can read the manpage online or by running man ping for more information on the usage.

Here's an example of usage:

$ ping -T tsandaddr
PING ( 56(124) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=3.22 ms
TS: 63668917 absolute 534841740 absolute not-standard 1 not-standard 3

64 bytes from icmp_seq=2 ttl=64 time=6.59 ms
TS: 63669919 absolute 534842745 absolute not-standard 0 not-standard 6

64 bytes from icmp_seq=3 ttl=64 time=3.20 ms
TS: 63670920 absolute 534843743 absolute not-standard 1 not-standard 3

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 3.207/4.343/6.599/1.595 ms

Note that I've tried on my LAN. Some hops on the internet may reject IP packets with the timestamp option. (In fact, I cannot ping any internet host with -T, probably my ISP is rejecting my packets.)

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