HP StorageWorks 1510i Modular Smart Array iSCSI concepts and deployment guide (431338-002, July 2008)

iSCSI sess
ions and TCP connections overview
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, a
ll 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, and 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
transfe
rred between an iSCSI initiator and an iSCSI target.
• Discovery Session—a session only opened for target discovery.
The following image illustrates an iSCSI session:
newpage pi
1510i Modular Smart Array iSCSI concepts and deployment guide
11