Open-iSCSI is a high-performance, transport independent, multi-platform
implementation of RFC3720 iSCSI.

Open-iSCSI is partitioned into user and kernel parts.

The kernel portion of Open-iSCSI is a from-scratch code licensed under
GPL. The kernel part implements iSCSI data path (that is, iSCSI Read
and iSCSI Write), and consists of two loadable modules: iscsi_if.ko and
iscsi_tcp.ko.

User space contains the entire control plane: configuration manager,
iSCSI Discovery, Login and Logout processing, connection-level error
processing, Nop-In and Nop-Out handling, and (in the future:) Text
processing, iSNS, SLP, Radius, etc.

The user space Open-iSCSI consists of a daemon process called iscsid,
and a management utility iscsiadm.