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An object identifier (OID) is an extensively used identification mechanism jointly developed by ITU-T and ISO/IEC for naming any type of object, concept or "thing" with a globally unambiguous name which requires a persistent name (long life-time). It is not intended to be used for transient naming. OIDs, once allocated, should not be re-used for a different object/thing.

It is based on a hierarchical name structure based on the "OID tree". This naming structure uses a sequence of names, of which the first name identifies a top-level "node" in the OID tree, and the next provides further identification of arcs leading to sub-nodes beneath the top-level, and so on to any depth.

A critical feature of this identification mechanism is that it makes OIDs available to a great many organizations and specifications for their own use (including countries, ITU-T Recommendations, ISO and IEC International Standards, specifications from national, regional or international organizations, etc.).

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Frequently Asked Questions (FAQ)

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At each node, including the root, there is a requirement for some organization or standard to be responsible for allocating arcs to sub-nodes and recording that allocation (together with the organization the subordinate node has been allocated to), not necessarily publicly. This activity is called a Registration Authority (RA).

In the OID tree, RAs are generally responsible only for allocation of sub-arcs to other RAs that then control their own sub-nodes. In general, the RA for a sub-node operates independently in allocating further sub-arcs to other organizations, but can be constrained by rules imposed by its superior, should the superior so wish.

The registration tree is indeed managed in a completely decentralized way (a node gives full power to its children).
The registration tree is defined and managed following the ITU-T X.660 & X.670 Recommendation series (or the ISO/IEC 9834 series of International Standards).

Initially, it was left for each Registration Authority (RA) in the hierarchy to maintain its own record of allocation beneath that RA, and to keep those allocations private if it so chose. There was never any policing of this. An RA in the hierarchy was its own master and operated autonomously.

In the early 1990s Orange developed software for their internal use which was generic enough to provide a publicly available repository of OID allocations.

Information on OIDs is often buried inside the databases (perhaps sometimes paper) maintained by an immense number of RAs. The information can be hard to access and is sometimes private. Today this OID repository is regarded as the easiest way to access a large amount of the publicly available information on OIDs: Many OIDs are recorded but it does not contain all existing OIDs.

This OID repository is not an official Registration Authority, so any OID described on this web site has to be officially allocated by the RA of its parent OID. The accuracy and completeness of this OID repository rely on crowdsourcing, i.e. each user is welcome to contribute data.

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