Delayed ACK

A few weeks ago, during a technical group meeting I hold here in town, a question came up that is now the basis of our next meeting. Does every TCP segment get an ACK returned?

My¬†unqualified¬†answer to this question was “No” as I had troubleshot some connections before and noticed that not every TCP segment received was sent an ACK. When challenged on this I couldn’t give the technical background for this just that this was my experience. Of course others in the group had different experiences so the only way to solve this was to do the research. Continue reading