Fibre Channel Addressing and Routing World-Wide Names
How to… interpret worldwide names The guide to uniquely identifiable names.
Chris Evans October 08, 03
All devices on a storage area network need to be uniquely identifiable. This is to ensure that data transmission occurs between the correct source and target device across a SAN fabric or loop.
In the Ethernet world, devices are uniquely identified by their MAC (media access control) address. This is a set of 6 hexadecimal pairs of numbers guaranteed to be assigned to a unique network card or device. In the SAN world, host bus adaptors and other SAN devices also utilise a unique identifier. With a little knowledge, we can interpret these codes to ensure that when we are cabling SAN infrastructures, we can correctly identify our connected devices and validate that cabling work has been performed correctly.
The SAN equivalent of a MAC address is the worldwide name (WWN). You will also see references to WWPN (Worldwide Port Name) and WWNN (Worldwide Node Name). Usually, the WWPN is the name you will more likely use as it is the name an HBA will present when logging into a SAN fabric. Worldwide Names consist of 16 hexadecimal digits grouped as 8 pairs. These are written with colon characters separating each pair. Some WWN examples are shown below:
The format of the WWN is defined by the IEEE, The Institute of Electrical and Electronics Engineers, a global (non-profit) organisation responsible for setting and maintaining a large number of IT standards. You can find full details of the WWN standard from the IEEE but here’s a quick breakdown.