[mortenlarsen]

This video explains and show the same concept for copper cables in a very simple and hands on way: "Cheap and simple TDR using an oscilloscope and 74AC14 Schmitt Trigger Inverter" https://www.youtube.com/watch?v=9cP6w2odGUc

[_trampeltier]

This very old video does it all explain better than all todays videos. The models are just so simple, no animations.

https://m.youtube.com/watch?v=DovunOxlY1k

[jaywalk]

Some NICs and managed switches can do it as well. Well, I should say that most can do it (as in the hardware is capable) but only some actually expose the functionality.