Bandwidth refers to the total amount of data that can flow through a link in a network at any one time. Different parts of a network often have radically different bandwidths. These differences usually are determined by a combination of equipment capabilities and cost.
For example, Ohio University's on-campus network uses high-speed, industry standard equipment that provides more bandwidth than currently is consumed. This equipment is easily upgradeable, and the cost of adding bandwidth between buildings and users is dependent only on the cost of installing new equipment. As a result, most people never even think about bandwidth when accessing their e-mail, the eDirectory, or one of Ohio University's many campus web sites. Because of our campus network's design, access to such services is, in effect, instantaneous.
Our Internet link, on the other hand, is much more limited. In order to reach sites outside of Ohio University, we must lease digital circuits from companies or government agencies that specialize in Internet connectivity. The monthly cost of these circuits is quite high. Increasing our Internet bandwidth even a small amount usually results in a large increase in that monthly cost.