O

object identifier

A number that identifies an object class or attribute. Object identifiers (OIDs) are organized into an industry-wide global hierarchy. An object identifier is represented as a dotted decimal string, such as 1.2.3.4, with each dot representing a new branch in the hierarchy. National registration authorities issue root object identifiers to individuals or organizations, who manage the hierarchy below their root object identifier.

off-subnet addressing

The allocation of IP addresses from remote access servers to remote access clients that are not in a range defined by a subnet to which the remote access server is attached.

on-subnet addressing

The allocation of IP addresses from a remote access server to remote access clients that are in a range defined by a subnet to which the remote access server is attached.

Open Shortest Path First (OSPF)

A routing protocol used in medium-sized and large networks. This protocol is more complex than Routing Information Protocol (RIP), but it allows better control and is more efficient in propagation of routing information.

See also Routing Information Protocol (RIP).

operations master

A domain controller that has been assigned one or more special roles in an Active Directory domain. The domain controllers assigned these roles perform operations that are single-master (not permitted to occur at different places on the network at the same time). Examples of these operations include resource identifier allocation, schema modification, PDC emulation, adding and removing domains to and from the forest, and tracking changes to security principals across all domains in a forest.

See also Active Directory.

See also domain controller.

See also infrastructure master.

See also PDC emulator master.