Virtual call capability

In telecommunication, a virtual call capability, sometimes called a virtual call facility, is a service feature in which:

a call set-up procedure and a call disengagement procedure determine the period of communication between two data terminal equipments (DTEs) in which user data are transferred by the network in the packet mode of operation
end-to-end transfer control of packets within the network is required
data may be delivered to the network by the call originator before the call access phase is completed, but the data are not delivered to the call receiver if the call attempt is unsuccessful
the network delivers all the user data to the call receiver in the same sequence in which the data are received by the network
multi-access DTEs may have several virtual calls in progress at the same time.