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iSCSI Concepts: Network Entities, Portals, and Nodes

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  • 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 “Network Entities, Portals and Nodes” 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

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 “iSCSI Target Sharing Two Target Portal Groups” shows an iSCSI Target sharing two Target Portal Groups to conduct multiple iSCSI sessions.

Figure 1-8 iSCSI Target Sharing Two Target Portal Groups

iSCSI Target Sharing Two Target Portal Groups