Out of Band Signaling - Creativyst(R) Glossary of developer terms.

Out-of-band signaling is a method of transmitting telephone control signals on a separate channel from the content (or "traffic") signals.

Early signaling systems carried the control signals on the same circuit as the user traffic; for example, the older in-band analog systems use this approach. The newer signaling systems, such as SS7, use a separate channel for signaling information. These systems are called common channel signaling (CCS) systems because a separate (common) channel is used for signaling. Some people call this approach out-of-band signaling and it is preferred to in-band signaling because it is more efficient and robust.

Two types of Out of Band Signaling exist today; Physical Out-Of-Band and Physical In-Band/Logical Out-Of-Band Signaling. SS7 is an example of the first type -- physical out-of-band signaling-- in which a separate physical channel is used for signaling. ISDN is an example of physical in-band/logical out-of-band signaling. With this later approach, signaling and user traffic share the same physical channel, but part of the channel is reserved only for signaling traffic; The remainder is reserved for user traffic, such as the telephone call. In ISDN, packets are multiplexed in time in order to subdivide the available bandwidth between logical channels.

	Out-of-band signaling is a method of transmitting telephone control signals on a separate channel from the content (or "traffic") signals. Early signaling systems carried the control signals on the same circuit as the user traffic; for example, the older in-band analog systems use this approach. The newer signaling systems, such as SS7, use a separate channel for signaling information. These systems are called common channel signaling (CCS) systems because a separate (common) channel is used for signaling. Some people call this approach out-of-band signaling and it is preferred to in-band signaling because it is more efficient and robust. Two types of Out of Band Signaling exist today; Physical Out-Of-Band and Physical In-Band/Logical Out-Of-Band Signaling. SS7 is an example of the first type -- physical out-of-band signaling-- in which a separate physical channel is used for signaling. ISDN is an example of physical in-band/logical out-of-band signaling. With this later approach, signaling and user traffic share the same physical channel, but part of the channel is reserved only for signaling traffic; The remainder is reserved for user traffic, such as the telephone call. In ISDN, packets are multiplexed in time in order to subdivide the available bandwidth between logical channels.
	In Band Signaling SS7