Have you ever observed the output of ping command … and wonder what’s this “TTL” stand for
Pinging http://www.google.com [126.96.36.199] with 32 bytes of data:
Reply from 188.8.131.52: bytes=32 time=365ms TTL=242
Reply from 184.108.40.206: bytes=32 time=367ms TTL=242
Reply from 220.127.116.11: bytes=32 time=370ms TTL=242
Reply from 18.104.22.168: bytes=32 time=366ms TTL=242
Each IP packet has a Time to Live (TTL) section that keeps track of the number of network devices the packet has passed through to reach its destination. The server sending the packet sets the initial TTL value, and each network device that the packet passes through then reduces this value by 1. If the TTL value reaches 0, the next network device will discard the packet.
This mechanism helps to ensure that bad routing on the Internet won’t cause packets to aimlessly loop around the network without being removed. TTLs therefore help to reduce the clogging of data circuits with unnecessary traffic.