type of communication on a communications medium that is sent immediately and directly and isn't held up by any non-out-of-band messages already in the pipeline

adj. Refers to a sentinel or otherwise exceptional value which is distinct from all normal values which can appear in some context (e.g. in a set of function return values, etc.). Compare in-band. Example: EOF (see question 12.1).

In telephony, information carried outside of the audio or voice channel.

The technique of transmitting controlling information over a separate channel to the LAN the information is controlling. This allows access to network devices even when the network is not functioning.

Refers to the process by which data (usually DTMF keystrokes) is transmitted on some path other than the audible voice path.

Pertaining to user-specific data that has meaning only for connection-oriented (stream) sockets. AS/400 generally receives stream data in the same order that it was sent. OOB data is received independent of its position in the stream (independent of the order in which it was sent).