International variants of signalling protocols, such as International ISUP and #5, in addition to the relevant national signalling protocols.
ISDN User Part or ISUP, a feature of Public Switched Telephone Networks
The call is switched using a call set up protocol (usually ISUP) between the telephone exchanges under an overall routing strategy.
ISUP |
Media Gateway Controller talk with each other using SIP, H.323 or ISUP