Brocade iSCSI Gateway Service Administrator's Guide - Supporting Fabric OS v5.3.0 (53-1000440-01, June 2007)

2 iSCSI Gateway Service Administrator’s Guide
Publication Number: 53-1000440-01
Overview of iSCSI gateway service
1
HOW ISCSI SESSIONS ARE TRANSLATED
The iSCSI gateway enables applications on an IP network to use an iSCSI initiator to connect to FC
targets. The iSCSI gateway translates iSCSI protocol to Fibre Channel Protocol (FCP), bridging the IP
network and FC SAN. The following figure shows a basic implementation.
FIGURE 2 iSCSI gateway service basic implementation
The Brocade FC4-16IP blade acts as an iSCSI gateway between FC-attached targets and iSCSI
initiators. On the iSCSI initiator, iSCSI is mapped between the SCSI driver and the TCP/IP stack. At
the iSCSI gateway port, the incoming iSCSI data is converted to FCP (SCSI on FC) by the iSCSI
virtual initiator, and then forwarded to the FC target. This allows low-cost servers to leverage an
existing FC infrastructure.
To represent all iSCSI initiators and sessions, each iSCSI portal has one iSCSI virtual initiator (VI) to
the FC fabric that appears as an N_Port device with a special WWN format. Regardless of the
number of iSCSI initiators or iSCSI sessions sharing the portal, Fabric OS uses one iSCSI VI per
iSCSI portal.
The following figure shows the interaction of different layers from the iSCSI initiator stack to the FC
target stack, including the iSCSI gateway service used during protocol translation.
FIGURE 3 iSCSI-to-FC translation
iS CS I
initiato r
iS CS I v irtual
initiato r (V I)
iS CS I v irtual
target (V T )
SAN
IP
network
IP
por ta l
FC
por tal
FC4-16IP iSCSI gateway
FC
IP
FC
target 1
FC
target 2
LUNs
LUNs
iS C S I gateway service
Storage
(device s erver)
SCSI
FCP
FC
FC target
Application
SCSI
iS C S I
TCP/IP
iS CS I in itia to r
FCP (FC-4)
FC (FC-2/FC-3)
iS C S I
TCP/IP
iS CS I v irtual
initiato r (V I)
iS CS I v irtual
target (V T )
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