An optional global-scope identifier for this connectivity unit. It MUST be a WWN for this connectivity unit or 16 octets of value zero. WWN formats requiring fewer than 16 octets MUST be extended to 16 octets with trailing zero octets, Left justified, zero filled, If a WWN is used for connUnitId, the same WWN MUST be used for connUnitGlobalId. When a non-zero value is provided, it SHOULD be persistent across agent and unit resets. It SHOULD be globally unique. It SHOULD be one of these FC-PH/PH3 formats: IEEE (NAA=1) IEEE Extended (NAA=2) IEEE Registered (NAA=5). IEEE Registered extended (NAA=6).

Use of the IEEE formats allows any IEEE-registered vendor to assure global uniqueness independently. The following are some references on IEEE WWN formats: http://standards.ieee.org/regauth/oui/tutorials/fibreformat.html http://standards.ieee.org/regauth/oui/tutorials/fibrecomp_id.html

If one or more WWNs are associated with the connUnit via other management methods, one of them SHOULD be used for connUnitGlobalId. If there is not a WWN assigned specifically to the connUnit, there is some merit, though not a requirement, to using a WWN assigned to (one of) its permanently attached FC/LAN interface(s). This can not risk uniqueness, though. As a counterexample, if your agent runs in a host and the host has an HBA, it is quite possible that agent, host, and HBA will all be distinct connUnits, so the host and agent can not use the WWN of the HBA. Another example: If your hub has a built-in Ethernet port, it might be reasonable for the hub to use its MAC address (prefixed with the appropriate NAA) as its connUnitId. But if the Ethernet were a replaceable PCCard, the hub should have an independent ID.