iSCSI Session and TCP Connections

In an iSCSI session, communication between an initiator and a target occurs over one or more TCP connections. The TCP connections carry control messages, data digests, SCSI commands, parameters, and data, all encapsulated in iSCSI Protocol Data Units (iSCSI PDUs).

The TCP connections that link an initiator with a target, forming an iSCSI session, are comparable to a SCSI I_T nexus.

An initiator sees one “target image” across all of the connections in a session. A target also sees one “initiator image” across all of the connections in a session.

iSCSI defines two types of sessions:

Normal Operational Session - a session in which SCSI commands, data and responses can be transferred between an iSCSI initiator and an iSCSI target.
Discovery Session - a session only opened for target discovery.

Figure 1-5 An iSCSI Session

iSCSI Session and TCP Connections

Technical documentation

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