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General
A variant of the EUI schema exists as the world wide name (WWN) identifier used within storage systems (SCSI, iSCSI, SATA, ADAPTI, Fiber Channel, and SAS). For historical reasons, the WWN is a 60-bit OUI based identifier.
The IEEE defined 60-bit extended unique identifier (EUI-60) is a concatenation of a 24-bit Organizationally Unique Identifier (OUI) value administered by the IEEE Registration Authority and a 36-bit extension identifier assigned by the organization with that OUI assignment.
The IEEE administers the assignment of 24-bit OUI values. The assignments of these values are public, so that a user of an EUI-60™ value can identify the manufacturer that provided the value[1]. The IEEE has no control over the assignments of 36-bit extension identifiers and assumes no liability for assignments of duplicate EUI-60 identifiers assigned by manufacturers.
Application restrictions
Given the minimal probability of consuming all the EUI-60 identifiers, the IEEE/RAC places minimal restrictions on their use within standards. Their major use is to distinctively identify hardware instances of disk drives within existing applications.
Users of EUI-60 applications should be aware if their requirement to avoid collisions between EUI-60 values and EUI-64/EUI-48 identifiers encapsulated within 64-bit values. See Nonoverlapping assignments for details.
The IEEE/RAC reviews draft IEEE standards for correctness and clarity of EUI-60 usage. The IEEE/RAC restricts the use of EUI-64 identifiers within future applications, where the use of an EUI-64 is preferred. If the EUI-60 is referenced within non-IEEE standards, there shall not be any reference to IEEE unless approved by the IEEE/RAC. The main purpose of IEEE/RAC review is to ensure eventual migration EUI-60 to EUI-64 identifiers within new applications.
Manufacturer-assigned identifiers
The manufacturer identifier assignment allows the assignee to generate approximately 64 billion (64x109) unique EUI-60 values, by varying the last 36 bits. The IEEE intends not to assign another OUI value to a manufacturer of EUI-60 values until the manufacturer has consumed, in product, the preponderance (more than 90%) of this block. It is incumbent upon the manufacturer to ensure that large portions of the block are not left unused in the consumption process.
60-BIT EXTENDED UNIQUE IDENTIFIER FORMAT TUTORIAL
Byte/nibble sequence formats
The first 24 bits of a 60-bit global identifier (EUI-60) carries the OUI value assigned to the organization by the IEEE Registration Authority. The remaining 40-bits of this identifier is assigned by that organization with that OUI assignment.
For example, assume that a manufacturer's IEEE-assigned OUI value is AC-DE-48 and the manufacturer-selected extension identifier for a given component is 2.3.4.5.6.7.A.B.C. The EUI-64 value generated from these two numbers is AC-DE-48:2.3.4.5.6.7.A.B.C.
Some standards specify an EUI-60 by a string of 15 nibbles, labeled here as nibble 0 through 15. For those standards, the format of the EUI-60 is illustrated below. Although different standards may specify different bit-transmission orders, nibbles are normally transmitted in an ascending index-value order.
| OUI | extension identifier | field
| | |
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | nibble
A C D E 4 8 2 3 4 5 6 7 A B C | hex
Numerical formats
Other standards specify an EUI-60 to be a numerical value, upon which computations (such as base/bounds or bit selections) can be performed. For those standards, the format of the EUI-60 is illustrated below:
ACDE48234567ABC16
To ensure unique representations within 64-bit values, manufacturers must not use the EUI-64 value corresponding to an assigned EUI-60 value. For example: if an EUI-60 is assigned to ACDE48234567ABC16, the EUI-64 value of ACDE48234567ABC016 cannot be assigned. A simpler (but more wasteful) strategy is also allowed: if an EUI-60 is assigned to ACDE48234567ABC16, EUI-64 values in the range of ACDE48234567ABC016 to ACDE48234567ABCF16 can be disallowed.
[1]Except for private OUI
values, where the owner of the OUI value is
confidential. These remain private.
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