See ISDN User Part.
ntegrated ervices Digital Network ser art ISUP is a layer of the SS7 protocol; ISUP messages are connection-oriented messages used to set up and tear down telephone calls; ISUP defines a handshaking protocol that initiates the phone call, reserves a path for the voice or data between the originating and destination devices, and ultimately releases the call; note that despite the name of this part of the SS7 stack, ISUP messages are not limited to ISDN calls. Performance Technologies' SS7 Tutorial
ISDN User Part (SS7). ISDN User Part is part of the SS7 (Signaling System No.7) protocol layer and used in the setting up, management, and release of trunks that carry voice and data between calling and called parties. ISUP Trunk Signaling is an important Connectivity and Interoperability Services offered by VeriSign.
Signaling System 7 ISDN User Part
ISDN Signaling User Part (signaling)
ISDN User Part. Used to set up and tear down all circuits used for data or voice calls in the PSTN.
Integrated Services User Part
ISDN User Part. The portion of SS7 that handles call control for ISDN-type calls.