A World Wide Name (WWN) or World Wide Identifier (WWID) is a unique identifier used in storage technologies including Fibre Channel, Advanced Technology Attachment (ATA) or Serial Attached SCSI (SAS). A WWN may be employed in a variety of roles, such as a serial number or for addressability; for example, in Fibre Channel networks, a WWN may be used as a WWNN (World Wide Node Name) to identify a switch, or a WWPN (World Wide Port Name) to identify an individual port on a switch. Two WWNs which do not refer to the same thing should always be different even if the two are used in different roles, i.e. a role such as WWPN or WWNN does not define a separate WWN space. The use of burned-in addresses and specification compliance by vendors is relied upon to enforce uniqueness.
World Wide Port Name, WWPN, or WWpN, is a World Wide Name assigned to a port in a Fibre Channel fabric. Used on storage area networks, it performs a function equivalent to the MAC address in Ethernet protocol, as it is supposed to be a unique identifier in the network.
A World Wide Node Name, WWNN, or WWnN, is a World Wide Name assigned to a node (an endpoint, a device) in a Fibre Channel fabric. It is valid for the same WWNN to be seen on many different ports (different addresses) on the network, identifying the ports as multiple network interfaces of a single network node.