Voice Over IP

ISUP

This book has discussed SS7 and ISDN as separate subjects. Indeed, they are separate, and they perform different operations in a transport and signaling network architecture. However, SS7 and ISDN are "partners" in that ISDN assumes SS7 will set up the connections within a network and SS7 assumes ISDN will set up connections at network boundaries (outside the network). Therefore, we can view ISDN as a user network interface (UNI) operating between the user device and the network node, and we can view SS7 as a network node interface (NNI) operating between the nodes within the network. Of course, nothing precludes using SS7 as an internetworking interface allowing two networks to communicate with each other.

The ISDN user part (ISUP) is used ...