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.