Section 1 identifies the WWN as an extended format WWN. Section 2 is a vendor specific code and can be used to identify specific ports on a node or to extend the serial number (section 4) of the WWN. Section 3 identifies the vendor. Section 4 is the unique vendor-supplied serial number for the device.
IEEE Registered Name (NAA=5)
Format 5 enables vendors to create unique identifiers without having to maintain a database of serial number codes. This format tends to be used by hardware vendors to create unique WWN values based on the serial number and physical port number of hardware devices such as disk arrays. The format has 3 sections, using the EMC example we can illustrate this.
Section 1 identifies this as a registered name WWN. Section 2 identifies the vendor. Section 3 is a vendor-specific generated code, usually based on the serial number of the device, such as a disk subsystem. The hardware vendor will use an algorithm to generate the WWN. The EMC algorithm is quite complex and for disk subsystems is based on the array serial number and the port number. The code demonstrated above represents a WWN for port 3aa on a disk frame with serial number 123456789.