HP-UX iSCSI Software Initiator Support Guide, HP-UX 11i v1 and 11i v2, July 2005

Chapter 1

iSCSI Overview

iSCSI Concepts: Network Entities, Portals, and Nodes

• Network Entity - a device or gateway that is accessible from the IP network. A network entity must

have one or more network portals. Each network portal can be used by one or more iSCSI nodes within

that network entity to gain access to the IP network.

• Network Portal - a component of a network entity that has a TCP/IP network address and may be used

by an iSCSI node within that network entity for the connection(s) within one of its iSCSI sessions.

A network portal in an initiator is identified by its IP address.

A network portal in a target is identified by its IP address and its listening TCP port.

• iSCSI Node - a single iSCSI initiator or iSCSI target. There can be one or more iSCSI nodes within a

network entity.

Figure 1-7 provides an example of two iSCSI nodes (targets in this case) sharing network portals within the

same network entity.

Figure 1-7 Network Entities, Portals and Nodes

• Portal Groups - a set of network portals within a network entity that share network connections and

can collectively coordinate an iSCSI session.

• Target Portal Group (TPG) - Although iSCSI initiators and iSCSI targets use portal groups to

coordinate iSCSI sessions, only target portal groups are used directly in the iSCSI protocol.

• Target Portal Group Tag (TPGT) - iSCSI portal groups that are associated with target nodes are

identified by a numerical target portal group tag ranging from 0 to 65535.

• Target Session Identifying Handle (TSIH) - a tag generated by an iSCSI target to identify an iSCSI

session with a specific iSCSI initiator. The TSIH is generated during session establishment.

Figure 1-8 shows an iSCSI Target sharing two Target Portal Groups to conduct multiple iSCSI sessions.