How does traceroute map the route a packet travels from point A to point B?

How does traceroute map the route a packet travels from point A to point B?
A . Uses a TCP timestamp packet that will elicit a time exceeded in transit message
B . Manipulates the value of the time to live (TTL) within packet to elicit a time exceeded in transit message
C . Uses a protocol that will be rejected by gateways on its way to the destination
D . Manipulates the flags within packets to force gateways into generating error messages

View Answer

Answer: B

Explanation:

Traceroute works by increasing the "time-to-live" value of each successive batch of packets sent. The first three packets have a time-to-live (TTL) value of one (implying that they make a single hop). The next three packets have a TTL value of 2, and so on. When a packet passes through a host, normally the host decrements the TTL value by one, and forwards the packet to the next host. When a packet with a TTL of one reaches a host, the host discards the packet and sends an ICMP time exceeded (type 11) packet to the sender. The traceroute utility uses these returning packets to produce a list of hosts that the packets have traversed en route to the destination.