An increasing number of libraries are signing up for cable modems, rather than point-to-point, frame relay, or DSL service from a telco. The attraction is broad bandwidth at low cost, but a drawback exists: The bandwidth is not guaranteed. Cable companies usually install nodes that serve several customers, the equivalent of the telephone party line. A customer may have 1.3 Mbps of bandwidth available during off-peak periods but can experience a drop to 160 Kbps during peak periods. That is not a problem for residential users, small businesses, and small branch libraries, but it is a problem for libraries seeking to support a score of automated library system and Internet users.
Before signing a contract for cable modems, a library should seek to negotiate a minimum bandwidth commitment. Although a commitment is not the same as a guarantee, it does mean that the number of users sharing the node will be limited and credits will be extended if the bandwidth drops below the committed level.