SS6 and SS7 implements out-of-band signaling, carried in a separate signaling channel, thus keeping the call control and speech paths separate. SS6 and SS7 are referred to as common-channel signaling (CCS) protocols, or Common Channel Interoffice Signaling (CCIS) systems.

Another element of in-band signaling addressed by SS7 is network efficiency. With in-band signaling, the voice channel is used during call setup which makes it unavailable for actual traffic. For long-distance calls,