# 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.

• Round-trip time is the time it takes for a packet that you send to get back to you. Now you can forget about the formulas, and rederive them to fit the definition. – Yuval Filmus Jan 29 '17 at 17:13
• Yes I know, but many examples don't take Transmission time into account. @Yuval – Mr. Sigma. Jan 30 '17 at 13:31
• @YuvalFilmus the question is whether the round trip time also includes the transmission delay of the packet? when should we include / not include – void Jan 25 '18 at 5:34