Do we include Transmission delay in Round trip time? Is RTT = $2*T_{Propagation delay}$ only. Or we include Transmission delay to send packets as well. Some examples include Transmission delay some not. I'm confused. Can anyone help.
Suppose you have two computers (A and B) both connected to a switch with cut-through forwarding. When you are interested about RTT between computer A and computer B, you'll omit transmission delay, because the switch transmits the frame to B as it arrives from A, so transmission delay is not significant. Now, suppose that our switch uses store-forward, in this case, when the frame arrives, the switch will first store it completely, and then sends it to B, so we have to deal with transmission delay.