cn TCP doubt

Question

what is the difference between round trip time and propagation delay in tcp/ip protocol?

 

is RTT = 2 * T_P  ?

Comments

In data link layer, it is true that RTT = 2 * Tp. However, in Transport layer (TCP), the RTT is NOT fixed as the Tp itself is not constant. Also, the Tp for a data packet from one end point to another might not be same as the Tp for the ACK packet from receiver back to the sender.

Answer 1

Propagation delay:  time required for the first bit to travel from the sender to the receiver. And it depends on physical medium of the link.

propagation time=distance/propagation speed

Round trip time:  it is the length of time it takes for a signal to be sent and the length of time it takes for an acknowledgement of that signal to be received.

i.e, RTT =2*Propagation time