out-of-band signaling and control - Computer Definition
Signaling and control that takes place over frequencies (e.g., in guard bands) or in time slots separate from those that carry user payload. In an analog context, out-of-band signaling can take place over the guard bands that separate channels. T-carrier signaling clearly is in-band rather than out-of-band, as it involves bit robbing, which periodically replaces payload bits with signaling bits. E-carrier signaling and control occurs exclusively in time slots reserved for that purpose. Packet technologies such as frame relay, Internet Protocol (IP), asynchronous transfer mode (ATM), and X.25 variously include headers and trailers that support out-of-band signaling, and use separate signaling packets for various network management purposes. Truly out-of-band signaling takes place over an entirely separate path and even a separate network, as is the case with Signaling System 7 (SS7). In any case, out-of-band signaling and control does not directly compete with payload for bandwidth. See also analog, ATM, digital, E-carrier, frame relay, guard band, header, in-band signaling and control, IP, network management, packet, payload, SS7, T-carrier, trailer, and X.25.