title: What's the difference between link-layer and e.g. transport-layer reliability?
body: <p>I have googled this and been sent to questions on stackoverflow a couple of times, but I am still not convinced. They simply say that link-layer reliability concerns itself with single hop, and higher layer reliablity (for instance transport layer reliability) concerns itself with end-to-end reliability.</p>
  
  <p>But won't the sum of all reliable single hops be the same as end-to-end reliablity? So in the end, what's really the difference?</p>