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 192.168.1.1

PING 192.168.1.1 (192.168.1.1) 56(124) bytes of data.

64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=3.22 ms

TS:     192.168.1.3 63668917 absolute

    192.168.1.1 534841740 absolute not-standard

    192.168.1.1 1 not-standard

    192.168.1.3 3



64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=6.59 ms

TS:     192.168.1.3 63669919 absolute

    192.168.1.1 534842745 absolute not-standard

    192.168.1.1 0 not-standard

    192.168.1.3 6



64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=3.20 ms

TS:     192.168.1.3 63670920 absolute

    192.168.1.1 534843743 absolute not-standard

    192.168.1.1 1 not-standard

    192.168.1.3 3



^C

--- 192.168.1.1 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.)