Communication Manager receives the digits dialed by the caller from the network and translates the dialed digits as a VDN which defines the service required by the caller. The VDN also serves as the application number that Communication Manager sends to the reporting adjuncts for call and agent handling statistical report generation.

VDNs are assigned to different vectors for specific call treatment. Any number of VDNs can point to the same vector. As a result, the same sequence of treatments can be given to calls that reach the system from different numbers or from different locations.