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Target are protected from unauthorized iSCSI access. Mutual CHAP provides an
added protection over One-Way CHAP for iSCSI communications on the Storage
Network. See CHAP and One-Way CHAP.
One-Way CHAP – Username and Secret in the Target (iS5xx iSCSI Bridge) that an
initiating device must use in order for the Target to authenticate the initiator for
communications. When the Initiator tries to contact the Target, the Target will
challenge the initiator to provide the correct Secret. If it is not provided, the Target
will not communicate with the Initiator. In this way, the Target device will not be
able to be accessed casually by other computers that do not have the One-Way CHAP
Secret, but can communicate on the same network. Both Microsoft’s iSCSI Initiator
software and the iS5xx iSCSI Bridges have the capability of setting both One-Way
and Mutual CHAP for secure system communications. See CHAP and Mutual CHAP.
SAN – Storage Area Network. A network of storage disks. In large enterprises, a
SAN connects multiple servers to a centralized pool of disk storage.
SCSI – The Small Computer System Interface standard for interfacing multiple
computers and devices. SCSI has three defined methods of parallel signal
communications, Low Voltage Differential (LVD), Single-Ended (SE) and High
Voltage Differential (HVD). Most LVD SCSI devices are Multimode, which allows
them to be backwards compatible with SE. The backwards compatibility is called
LVD/MSE.
SCSI Initiator/Host – A device that begins a SCSI transaction by issuing a command
to another device (the SCSI target), giving it a task to perform. SCSI host bus
adapters are normally considered to be initiators.
SCSI Target – A SCSI device that executes a command from a SCSI initiator to
perform some task. SCSI hard drives, tape drives and other storage devices are
normally considered to be targets.
SE – Single-Ended. Type of signal transmission used by SCSI. SE supports cable
lengths of up to 6 meters.
Subnet – A division of a network into an interconnected, but independent, segment, or
domain. The subnet limits the number of nodes (clients, servers) that have to
compete for available bandwidth to a confined geographic area.
Subnet Mask – The technique used by the IP protocol to determine which network
segment packets are destined for. The subnet mask is a binary pattern that is stored in
the client machine, server or router and is matched with the IP address.
Terminator – A hardware component that is connected at each end of a SCSI cable
chain. The terminator may be external or internal to the device.