PSTN: Switching and Signaling

As the PSTN’s global reach and capabilities become more extensive, signaling
became the most significant security concern within the PSTN. In its early days, signaling
was no more complicated than taking the phone off-hook to let an operator
know you wanted to make a call. Dialing gradually became more automatic, first for
operators, then later for subscribers.Today’s direct-dial networks,VoIP gateways, and
myriad protocols only serve to increase the complexities and risks when it comes to
signaling.