A scheduler for controlling when N entities, where N is an integer greater than or equal to one, are operated upon by a server. The scheduler includes a starting time memory. The starting time memory has only arriving times which are greater than virtual time. The scheduler also includes a finishing time memory. The finishing time memory has finishing times of the N entities whose starting times are less than or equal to virtual time. Additionally, the scheduler includes a virtual clock that keeps track of virtual time so the arriving times and finishing times can be identified. Moreover, the scheduler is also comprised of a controller for choosing entities to be operated upon by the server from the finishing time memory. A method of scheduling when a server provides service to entities.