Trace route

The history of the route is recorded as the round-trip times of the packets received from each successive host (remote node) in the route (path); the sum of the mean times in each hop is a measure of the total time spent to establish the connection.

The time-to-live (TTL) value, also known as hop limit, is used in determining the intermediate routers being traversed towards the destination. Routers decrement TTL values of packets by one when routing and discard packets whose TTL value has reached zero, returning the ICMP error message ICMP Time Exceeded.

Traceroute works by sending packets with gradually increasing TTL value, starting with TTL value of one.
The next set of packets are given a TTL value of two, so the first router forwards the packets, but the second router drops them and replies with ICMP Time Exceeded.


The sender expects a reply within a specified number of seconds.

Traceroute employs User Datagram Protocol (UDP) datagrams by default, with destination port numbers ranging from 33434 to 33534.
The traceroute utility usually has an option to instead use ICMP Echo Request (type 8) packets, or to use TCP SYN packets.

Example of traceroute output:

Русский перевод

traceroute.gif (19.2 KB) Andrii Arsirii, 01/07/2017 01:44 PM

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