The ITU-TS (once known as the CCITT) developed a digital signaling standard in the mid-60s called Signaling System #6 that would revolutionize the telephone industry. Based on a proprietary, high-speed data communications network, SS6 later evolved into SS7, which has now become the signaling standard for the entire world.

The secret to its success lies in the message structure of the protocol and the network topology. The protocol uses messages, much like X.25 and other message-based protocols, to request services from other entities. These messages travel from one network entity to another, independent of the actual voice and data they pertain to, in an envelope called a packet.

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