What is SS7 – ISUP ?
SS7 (signaling System 7) or “out-of-band” signaling is the most widely used signaling system where the signals are transmistted on a seperate physical channel from the call channel. Because of that, SS7 network can examine all parts of a call route for free lines and allocate them at once. This leads to a more efficient network and fast call setup times, generally about 3 seconds where as in early CAS systems this might take about 20 seconds. Also it has many more advantages compared to CAS (Channel Associated Signaling) or “in-band” signaling where signals and the call are transmitted on the same channel.
