What is the term Bandwidth?

Bandwidth is a term used to describe how much information can be transmitted over a connection. Bandwidth is usually given as bits per second, or as some larger denomination of bits, such as Megabits per second, expressed as kbit/s or Mbit/s. Bandwidth is a gross measurement, taking the total amount of data transferred in a given period of time as a rate, without taking into consideration the quality of the signal itself.

Throughput can be looked at as a subset of bandwidth that takes into account whether data was successfully transmitted or not. While the bandwidth of a connection might be quite high, if the signal loss is also high, then the throughput of the connection will remain somewhat low. Conversely, even a relatively low-bandwidth connection can have a moderately high throughput if the signal quality is also high.

Bandwidth is most familiar to consumers because of its use by hosting companies or internet service providers. The sense in which bandwidth is used by most web hosting companies, that is, as a measure of total data transferred in a month, is not strictly correct. This measurement is more rightly referred to as data transfer, but the use of bandwidth by hosting companies is so pervasive that it has become accepted by the general public.

Many hosting providers place caps on the amount of bandwidth a site can transfer in a given period of time, usually a month, but sometimes twenty-four hours or a week. If the site exceeds its bandwidth allotment, the service is usually either suspended or else additional bandwidth is billed separately, often at a much higher cost than the base cost included with the hosting plan.

Some hosts offer so-called unlimited bandwidth plans, which in theory have an unlimited amount of data transfer per month. Usually the actual bandwidth, that is the per-second transfer of a connection, is somewhat limited on these services, ensuring data transfer for the site never becomes too large. If the bandwidth limit is met, speeds for users may be throttled down substantially, or service may even be interrupted.