Throughput

Question

Given that the bandwidth delay product determines the number of bits that a link can fill. The sender must send a data packet with bits (2 * bandwidth * delay). I don’t understand why the term bandwidth is multiplied by 2. Please explain the reason.

Answer 1

It depends on what you mean by "delay." If the delay is round-trip time (RTT), you will not multiply it by two. Presumably, in the formula you are looking at, the delay is a unidirectional transmission time, so you multiply it by 2 to estimate the RTT.

One RTT is the earliest time when you can receive confirmation for the first bit you transmitted, so your window should be so large as to fill the channel.

Answer 2

The delay in your case is the propagation delay, which is the time that a signal (message) takes to propagate from sender to receiver.

It is multiplied by 2 because the link is bidirectional, i.e. The sender and receiver can simultaneously send data simultaneously, i.e. to completely fill out the link needed to multiply the propagation delay by 2, and this term is known as round off time (RTT).

bandwidth-delay product = RTT * bandwidth bandwidth-delay product = 2 * propagation delay * bandwidth 

Where

 RTT = 2 * propagation delay 

Answer 3

I think this product only works with tcp / ip, not udp / ip. since only tcp needs confirmation about the data being sent.