Propagation Delay

Propagation delay is the delay associated with the time it takes for an electronic signal to travel across the telecommunications infrastructure. This is mainly dependent on the distance traveled by the signal and is governed by the laws of physics. As a rule of thumb a figure of 0.6 ms per 100km can be used. So for two cities 500km apart, a one-way propagation delay of around 3ms can be expected.

In minimizing propagation delay, it’s the actual path that the electrons traverse that is important. Having a network topology that routes packets from London to Paris via Madrid is clearly not efficient and would result in a far greater delay than if the data packets go directly from London to Paris. In calculating distances, allowance must also be made for the fact that the ‘as the crow flies’ distance is not always the same as the fiber path distance. This is particularly true when there are large physical barriers (e.g. oceans) in the way.

If high-speed access circuits and high-speed data switches are used, the total network latency between any two sites that are not in the same city tends to be dominated by propagation delay. To minimize propagation delay, Vital Voice & Data’s network topology links major financial centers together using the shortest, most direct route. This minimizes the distance required to send data and so reduces propagation delay.