A terminal server is a specialize computer which aggregates multiple communication channels together. Because these channels are bidirectional, two models emerge: Multiple entities connecting to a single resource, and a single entity connecting to multiple resources. Both of these models are widely used. Both physical and virtual resources can be provided through a terminal server: centralized computing can provide multiple users access to a remote virtual operating system. Access Providers often use terminal servers to terminate physical connections to their customers, for example customers who get Internet through some form of modem.