Organizationally Unique Identifier

Organizationally Unique Identifier

An Organizationally Unique Identifier (OUI) is a 24-bit number that is purchased from the Institute of Electrical and Electronics Engineers, Incorporated (IEEE) Registration Authority. This identifier uniquely identifies a vendor, manufacturer, or other organization (referred to by the IEEE as the 'assignee' ) globally or worldwide and effectively reserves a block of each possible type of derivative identifier (such as MAC addresses, group addresses, Subnetwork Access Protocol protocol identifiers, etc.) for the exclusive use of the assignee. The OUI is subsequently used by the assignee to create particular instances of these identifiers for various purposes, such as the identification of a particular piece of equipment (e.g., a network interface controller (NIC)) or the identification of a network protocol, and for use in various computer hardware products, including MAC addresses for Ethernet and other NICs (network interface cards), World Wide Names for Fibre Channel host bus adapters, and other Fibre Channel and Serial Attached SCSI devices.] .

64-bit Extended Unique Identifier (EUI-64):

::The EUI-64 is an identifier that is formed by concatenating the 24-bit OUI with a 40-bit extension identifier that is assigned by the organization that purchased the OUI – the resulting identifier is generally represented as a set of octets separated by dashes (hexadecimal notation) or colons (bit-reversed notation) as in FF-FF-FF-FF-FF-FF-FF-FF or FF:FF:FF:FF:FF:FF:FF:FF, as a string of 8 bytes as in {FF,FF,FF,FF,FF,FF,FF,FF}, or as a base 16 number as in FFFFFFFFFFFFFFFF16.

:::Note: According to the IEEE guidelines, the first four digits of the organizationally assigned identifier (i.e., the first four digits of the extension identifier) portion of an EUI-64 “shall not be FFFE16 or FFFF16” (i.e., EUI-64 identifiers of the form ccccccFFFEeeeeeeeeee and ccccccFFFFeeeeeeeeee are not allowed) – this is to support the encapsulation of MAC-48 and EUI-48 values into EUI-64 values.

Other Identifiers:

::There are other identifiers that may be formed using the OUI but those listed above are the most commonly used.

Encapsulating:

::Other identifiers, such as MAC-48 and EUI-48 values, can be contained within a larger identifier or 'container', such as EUI-64, by creating the larger identifier through a process of combining the smaller identifier with specified values placed in specified bit-positions within the larger identifier – this process is known as 'encapsulation' and is provided for the purpose of easing the transition from MAC-48 and EUI-48 to EUI-64 and to provide a mechanism for the conversion of MAC-48 and EUI-48 identifiers to EUI-64 in such a way that duplicate or conflicting values are avoided.

:::Encapsulation of MAC-48 within EUI-64 Example:

::::Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the MAC-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this MAC-48 identifier has the following binary transmission order:


 OUI | extension identifier | field
 1st | 2nd | 3rd | 4th | 5th | 6th | octet
 C A | E D | 8 4 | 3 2 | 5 4 | 7 6 | hex0011 0101 0111 1011 0001 0010 1100 0100 1010 0010 1110 0110 bits
 | | | | | | | | | | 
lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb

::::The same MAC-48 identifier after encapsulation within an EUI-64 has the following transmission order:


 OUI | MAC label | extension identifier | field 
 1st | 2nd | 3rd | 4th | 5th | 6th | 7th | 8th | order
 C A | E D | 8 4 | F F | F F | 3 2 | 5 4 | 7 6 | hex00110101 01111011 00010010 11111111 11111111 11000100 10100100 11100110 bits
 | | | | | | | | | | | | | | 
lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb lsb msb

::::The same MAC-48 identifier after encapsulation within an EUI-64 has the following significance order:


 OUI | MAC label | extension identifier | field 
 AC | DE | 48 | FF | FF | 23 | 45 | 67 | hex10101100 11011110 01001000 11111111 11111111 00100011 01000101 01100111 bits
 | | 
 most-significant-byte least-significant-byte 
most-significant-bit least-significant-bit

:::Encapsulation of EUI-48 within EUI-64 Example:

::::Assuming that an organization has registered the OUI of AC-DE-48 and that the organization has created the EUI-48 value of AC-DE-48-23-45-67 by concatenating the extension identifier 23-45-67, this EUI-48 identifier has the following format in significance order:


 company_id | extension identifier | field 
 AC | DE | 48 | 23 | 45 | 67 | hex10101100 11011110 01001000 00100011 01000101 01100111 bits
 | | 
 most-significant-byte least-significant-byte 
most-significant-bit least-significant-bit

::::The same EUI-48 identifier after encapsulation within an EUI-64 has the following format in significance order:


 company_id | EUI label | extension identifier | field 
 AC | DE | 48 | FF | FE | 23 | 45 | 67 | hex10101100 11011110 01001000 11111111 11111110 00100011 01000101 01100111 bits
 | | 
 most-significant-byte least-significant-byte 
most-significant-bit least-significant-bit

Individual Address Block

The Individual Address Block (IAB) is a block of identifiers that is formed by concatenating a 24-bit Organizationally Unique Identifier (OUI) that is owned "by the IEEE Registration Authority" with an additional 12-bit extension identifier that is assigned "by the IEEE Registration Authority" and then reserving an additional 12 bits for use by the assignee. The resulting 48-bit identifier uniquely identifies the assignee of the IAB and provides 4096 unique numbers for use by the organization that purchased the IAB. The assignee may create unique identifiers by concatenating a 12-bit extension identifier that is assigned by the organization that purchases the IAB in the bit positions occupied by the 12 additional bits mentioned previously. The purpose of the IAB is to allow organizations to purchase smaller blocks of identifiers at a reduced price.

The IEEE Registration Authority distinguishes between IABs and OUI-36 values. Both are 36-bit values which may be used to generate EUI-48 values, but IABs may not be used to generate EUI-64 values. At the time of writing, the Authority charges the same amount for an IAB or an OUI-36.

:Example of EUI-48 created within an IAB: An EUI-48 identifier is formed by combining the 36-bit IEEE assigned IAB base value with a 12-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 12-bit extension identifier is hhh16, then the EUI-48 value generated by combining these two numbers is FF-FF-FF-FF-Fh-hh.

:Note:There are also IAB based sequences that are formed by combining the 36-bit IEEE assigned IAB base value with the 4-bit extension identifier assigned by the organization – e.g., if the IEEE assigned IAB base value is FF-FF-FF-FF-F0-00 and the 4-bit extension identifier is 0h16, then the CDI-40 value generated by combining these two numbers is FF-FF-FF-FF-Fh.

Compare to

* Globally Unique Identifier (GUID)
* Object identifier (OID)

References

External links

* [http://standards.ieee.org/faqs/OUI.html IEEE OUI FAQ]
* [http://standards.ieee.org/regauth/oui/index.shtml IEEE OUI and Company_id assignments]
* [http://standards.ieee.org/regauth/oui/oui.txt List of registered OUIs]
* [http://standards.ieee.org/faqs/OUI.html The IEEE Frequently Asked Questions, Registration Authority]
* [http://standards.ieee.org/regauth/oui/index.shtml The IEEE OUI Search Page]
* Wireshark's [http://www.wireshark.org/tools/oui-lookup.html OUI Lookup Tool] and [http://anonsvn.wireshark.org/wireshark/trunk/manuf MAC address list]

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