OOB

OOB stands for out-of-band, a term used across fields to describe data, signals, or actions that occur outside the main channel or path.

In telecommunications and IT, out-of-band signaling uses a separate control channel from the primary data path for setup, management, or fault handling. Out-of-band management refers to dedicated networks or interfaces used to configure and monitor devices (for example, server BMCs with IPMI, HP iLO, Dell DRAC) even when the production network is unavailable.

In security, out-of-band authentication relies on a separate channel to verify identity or authorize transactions, such as a hardware token or a code delivered by SMS or email.

In software and computing, OOB can mean out-of-bounds memory access—reading or writing beyond allocated memory, a frequent source of crashes and vulnerabilities. It also appears in machine learning as out-of-bag error estimates, computed from data not used to train a given model.

In gaming, OOB commonly refers to regions outside the designed game world, which players may reach through glitches or exploration beyond intended boundaries.

In networking, OOB data may refer to urgent data sent outside the main data stream, using features such as TCP urgent mode, though this usage is less common in modern practice.