un-named discovery session

A security feature for iSCSI discovery. The storage subsystem will not respond to global requests; rather, it will only respond to requests addressed specifically to this target. If un-named discovery sessions are disabled, an iSCSI initiator can only ask the target about a specific target or targets by iSCSI name. If the iSCSI initiator tries to ask for all targets, the target (storage subsystem) drops the request without answering, which makes it appear that the storage subsystem is not there.