iSCSI (Internet Small Computer Systems Interface)

iSCSI carries SCSI, the command set computers use to read and write blocks on disks, inside TCP/IP. A server acting as the initiator sends commands across an IP network to a storage system acting as the target, and the remote disk then appears to the server’s operating system as a locally attached drive. It is defined in RFC 7143, which consolidated the original RFC 3720. Because it runs over TCP/IP, iSCSI can be routed, which lets organisations build a storage area network on existing Ethernet and IP equipment.

The ISC2 exam outline names iSCSI as an example of a converged protocol. It is commonly compared with Fibre Channel over Ethernet, which also puts storage onto Ethernet but stays at layer 2 and is not routed over IP. Convergence brings shared exposure. iSCSI can authenticate initiators and targets with CHAP, in one direction or mutually, but that is optional, and the protocol does not encrypt the data it carries. Confidentiality needs IPsec or an isolated network, and storage traffic is commonly placed on a dedicated VLAN or a physically separate network.

Exam relevance: a scenario is likely to describe block storage reached over an IP network and ask what protects it. Candidates are expected to recognise that iSCSI on its own gives no confidentiality.