Out-of-band
Out-of-band activity is activity outside a defined telecommunications frequency band, or, metaphorically, outside of any primary communication channel. Protection from falsing is among its purposes. Examples General usage Out-of-band agreement, an agreement or understanding between the communicating parties that is not included in any message sent over the channel but which is relevant for the interpretation of such messages More broadly, communication by any channel other than the primary channel can be considered "out-of-band". For example, given a website's primary communication method is the internet, out-of-band communication may be an SMS message or even beeps produced by a speaker on the server itself. Telecommunications Out-of-band signaling, the exchange of call control information in a separate band from the data or voice stream, or on an entirely separate, dedicated channel Computing Out-of-band data, in computer networking, a separate stream of data from the main data stream Out-of-band management, in computer administration, system console access, even in the event of primary network subsystem failure Out-of-band authentication, user authentication over a network or channel separate from the primary network or channel; used in multi-factor authentication Out-of-band software documentation, documentation that is not provided together with the software it documents. This contrasts with Unix