In computer networking, a routing domain is a collection of networked systems that operate common routing protocol

Routing protocol

A routing protocol is a protocol that specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms. Each router has a priori knowledge only of...

s and are under the control of a single administration. For example, this might be a set of routers under a control of a single organization, some of them operating a corporate network, some others a branch office network, and the rest the data center network.

A given autonomous system

Autonomous system (Internet)

Within the Internet, an Autonomous System is a collection of connected Internet Protocol routing prefixes under the control of one or more network operators that presents a common, clearly defined routing policy to the Internet....

can contain multiple routing domains, or a set of routing domains can be coordinated without being an Internet-participating autonomous system.