I am currently in college for a bachelor's degree in Network Engineering, and one of my Professors explained in class that a traceroute that shows, for example, 15 hops is actually abstracting the path, and in reality many more nodes are involved. Is this true?
This contradicts everything I can find on traceroute. To my knowledge, traceroute works by sending ICMP (or UDP) packets to a specific destination with a TTL from 0 --> n until the destination is reached. The probe packets that are sent out time out at each location along the way in succession, producing an ICMP "time exceeded" reply, and finally a "port unreachable" message when reaching the destination.
I understand the imperfections of traceroute - for example, traceroute traffic may be blocked by certain gateways, or the TTL of the reply packet may be set to the probe's remaining TTL, causing it to never return to the sender.
However, after a lot of researching, I can't find anything referencing traceroute being inaccurate in the case of a traceroute that always returns the same path. Likewise, nothing referencing there being any "extra" hops not reported by traceroute (other than * * * hops that timed out with no reply).
I'm open to discussion, and I'm genuinely interested to know the answer to this.