An OID corresponds to a
node in the "OID tree" or hierarchy, which is formally defined using the ITU's
OID standard,
X.660. The root of the tree contains the following three
arcs:
Each node in the tree is represented by a series of integers separated by periods, corresponding to the path from the root through the series of ancestor nodes, to the node. Thus, an OID denoting
Intel Corporation appears as follows,
1.3.6.1.4.1.343
and corresponds to the following path through the OID tree:
Each node in the tree is controlled by an assigning authority, which may define child nodes under the node and delegate assigning authority for the child nodes. Continuing with the example, the node numbers under root node "1" are assigned by ISO; the nodes under "1.3.6" are assigned by the US Department of Defense; the nodes under "1.3.6.1.4.1" are assigned by
IANA; the nodes under "1.3.6.1.4.1.343" are assigned by Intel Corporation, and so forth.
Usage
ISO/IEC 6523 "International Code Designator" uses OIDs with the prefix "1.3".
IANA assigns
Private Enterprise Numbers (PEN) to companies and other organizations under the 1.3.6.1.4.1 node. OIDs down-tree from these are among the most commonly seen; for example, within SNMP MIBs, as LDAP attributes, and as vendor suboptions in the
Dynamic Host Configuration Protocol (DHCP).
In the
United States,
Health Level Seven (HL7), a standards-developing organization in the area of electronic health care data exchange, is the assigning authority at the 2.16.840.1.113883 (joint-iso-itu-t.country.us.organization.hl7) node. HL7 maintains its own
OID registry, and as of December 1, 2020 it contained almost 20,000 nodes, most of them under the HL7 root.
The
Centers for Disease Control and Prevention uses OIDs to manage the many complex values sets or "vocabularies" used in the Public Health Information Network (PHIN) Vocabulary Access and Distribution System (
VADS).