Unified Communication Manager - Class of Service
Source: Global Knowledge
Class of Service is a way of controlling which phone numbers a phone, gateway, voicemail port, etc. has access to. By creating multiple partitions and multiple Calling Search Spaces (CSS), an administrator can control which devices can make long-distance or international phone calls or calls to any other phone number. It can also control when these calls can be placed by applying time schedules to the partitions. Using the basic components of Partitions and CSSs, you can create just about any class of phone service model imaginable, to suit any need.