Outofband

Out-of-band (OOB) refers to a method of communication that uses a channel separate from the primary data path. It is used for management, control, or signaling and is designed to remain accessible even when the main network is down or congested. OOB is contrasted with in-band communication, where management traffic travels over the same path as user data.

In IT and networking, OOB management provides administrators with access to devices for configuration, monitoring, or recovery via dedicated interfaces or networks. Common implementations include serial console ports, dedicated management NICs, or OOB management appliances. Technologies and products often associated with OOB management include IPMI, SNMP, and vendor solutions such as HP iLO, Dell iDRAC, and Cisco out-of-band management. Benefits include BIOS-level access, remote recovery, and reduced risk of disrupting production traffic. Limitations involve additional hardware, the need for a separate network infrastructure, and the importance of securing the OOB path to avoid a single point of failure.

In telecommunications and networking protocols, out-of-band signaling uses a separate channel to establish and control communications, distinct from the media channel. Classic examples include SS7 signaling in traditional telephony and CAMEL in mobile networks. In software contexts, out-of-band data can refer to data sent outside the normal in-band stream, such as TCP urgent data; this capability is seldom relied upon in modern applications due to complexity and compatibility concerns.

Security considerations for OOB paths emphasize isolation, authentication, encryption, and strict access controls. Redundancy and monitoring are common practices to ensure ongoing management capability even under adverse conditions.