During a traceroute, which action does a router perform to the value in the Time To Live (TTL) field?

During a traceroute, the router decreases the Time To Live values of the packet sent from the traceroute by one during routing, discards the packets whose Time To Live values have reached zero, returning the ICMP error message ICMP time exceeded.

Explanation:

Traceroute performs a route tracing function in a network. It is a network diagnostic commands that shows the path followed, and measures the transit delays of packets across an Internet Protocol (IP) network, from the source to the destination, and also reports the IP address of all the routers it pinged along its path. During this process, the traceroute sends packets with Time To Live values that increases steadily from packet to packet; the process is started with Time To Live value of one. At the routers, the Time To Live values of the packets is gradually decreased by one during routing, and the packets whose Time To Live values have reached zero are discarded, returning the ICMP error message ICMP Time Exceeded