# What is Bandwidth Delay Product in networking?

This page describes bandwidth delay product and its purpose in networking and data communication.The formula and link on how to calculate bandwidth delay product is also mentioned.

## What is Bandwidth delay product?

The term is widely used for data communication in various wireless and wired systems. It indicates number of bits (or bytes) which can be transmitted before an ACK (acknowledgement) is received from the other end. In other words, it is estimation of number of bits "in transit" through the transmission medium.

The concept of bandwidth delay product can best be illustrated as shown in the figure. We can think it as link between two points of a pipe. The cross section represents bandwidth where as pipe length represents delay. Volume of pipe defines bandwidth delay product (BDP). The BDP defines the number of bits that can fill the link.

Examples of BDP for various systems are as follows.
➨Satellite network with data rate of 512 Kbps and RTT of 1000 ms, BDP = 512000 bits = 512 kbits = 64 KBytes
➨DSL with 2 Mbps data rate (i.e. bandwidth) and RTT of 50 ms, BDP = 100 kbits = 12.5 Kbytes
➨Ultra speed LAN with 100 Gbps and 30 µs RTT, BDP = 3 Mbits = 0.375 Mbytes

### What is the purpose of bandwidth delay product ?

• It helps in determining maximum amount of data on the network path at any time instant. At this time, data has been transmitted but not acknowledged yet.
• The network having larger bandwidth-delay product with greater than 105 bits is known as long fat network.
• One such example of such long fat network is Geostationary satellite link as it will have end to end transit time as well as link throughput higher.
• If the amount of data to be transmitted is in-sufficient in comparison to BDP, then the transmission link is not considered to be overloaded. Hence it can be concluded that protocol is functioning well below the peak efficiency of link.

## Bandwidth Delay Product Calculation

The formula used in bandwidth delay product calculation is mentioned above.