Difference between transmission delay and propagation delay?
Propagation delay is how long it takes one bit to travel from one end of the “wire” to the other (it’s proportional to the length of the wire, crudely).
Transmission delay is how long it takes to get all the bits into the wire in the first place (it’s packet_length/data_rate).
Another Definition of Propagation Delay and Transmission Delay:
Is the time it takes a bit to propagate from one router to the next; it is a function of the distance between the two routers, but has nothing to do with the packet’s length or the transmission rate of the link.
d: length of physical link
S: propagation speed in medium (~2x108m/sec)
so propagation delay is = d/s
This is the amount of time required to transmit all of the packet’s bits into the link. Transmission delays are typically on the order of microseconds or less in practice.
L: packet length (bits)
R: link bandwidth (bps)
so transmission delay is = L/R