# Bandwidth Delay Product

Computer NetworkComputer EngineeringMCA

Bandwidth delay product is a measurement of how many bits can fill up a network link. It gives the maximum amount of data that can be transmitted by the sender at a given time before waiting for acknowledgment. Thus it is the maximum amount of unacknowledged data.

## Measurement

Bandwidth delay product is calculated as the product of the link capacity of the channel and the round – trip delay time of transmission.

The link capacity of a channel is the number of bits transmitted per second. Hence, its unit is bps, i.e. bits per second.

The round – trip delay time is the sum of the time taken for a signal to be transmitted from the sender to the receiver and the time taken for its acknowledgment to reach the sender from the receiver. The round – trip delay includes all propagation delays in the links between the sender and the receiver.

The unit of bandwidth delay product is bits or bytes.

## Example

Consider that the link capacity of a channel is 512 Kbps and round – trip delay time is 1000ms.

The bandwidth delay product      = 512 × 103 bits/sec × 1000 × 10−3 sec

= 512,000 bits = 64,000 bytes = 62.5 KB

## Long Fat Networks

A long fat network (LFN) is a network having high bandwidth delay product which is greater than 105 bits.

Ultra – high-speed LANs (local area network) is an example of LFN. Another example is WANs through geostationary satellite connections.

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