Hi,
If you are talking about propagation delay and transmission time then there is a difference in these two terms , propagation delay means how much time your packet will take to reach from node A to node B, and transmission delay means that how much time your packet will take to be transmitted at node B.
As an example ,in optical networks, the propagation delay is higher than the data packet transmission time. For example, let us consider a network with diameter 3 km and data packets with size 1024 bits. In case of a channel with capacity 10 Mb/s and propagation speed of 2 × 108 km/s, the propagation delay is 15 μs while the data transmission time is 102.4 μs. In case of a wavelength with capacity of 1 Gb/s the data transmission time is 1.024 μs.
I hope this will help to understand the concept.
BR,
Arif Khan
please press helped me.