Question in the book that confuses me

Jasiono

Is there something wrong with this question in the book that I'm reading?



Shouldn't the ACK 2 be an ACK 4 because it got segments 1, 2 and 3 already, asking for number 4?

It asks for segment 5 because 5 was lost, and once 5 comes in it asks for segment 7.

Reliable Delivery.jpg

Jasiono

Then it asks this question:



To me this is reliable reliable delivery in both questions, but I just don't understand what is different about the original post and this one with the ACK 2 vs the ACK 4.

reliable 2.jpg