Security and secrecy*
			n Services require usually security & serrecy, e. g. reliable, shielded transfer. Especially for n rescue services n police n defense force n some special applications as telesurgery n Networks can provide this by using: n fixed lines (PSTN, frame relay) n flexible routing (SS7) n scrambling or encryption (PLMNs) n coding or ciphering  (in all modern telecom links & nets) n Often reassured in several network levels