Concept Guide
• If you congured ow-control, iSCSI uses the current conguration. If you did not congure ow-control, iSCSI auto-congures ow
control.
• iSCSI monitoring sessions — the switch monitors and tracks active iSCSI sessions in connections on the switch, including port
information and iSCSI session information.
• iSCSI QoS — A user-congured iSCSI class of service (CoS) prole is applied to all iSCSI trac. Classier rules are used to direct the
iSCSI data trac to queues that can be given preferential QoS treatment over other data passing through the switch. Preferential
treatment helps to avoid session interruptions during times of congestion that would otherwise cause dropped iSCSI packets.
• iSCSI DCBx TLVs are supported.
NOTE: After a switch is reloaded, powercycled, or upgraded, any information exchanged during the initial handshake is not
available. If the switch establishes communication after reloading, it detects that a session was in progress but could not obtain
complete information for it. Any incomplete information is not available in the show commands.
NOTE: After a switch is reloaded, powercycled, or upgraded, the system may display the ACL_AGENT-3-
ISCSI_OPT_MAX_SESS_LIMIT_REACHED: Monitored iSCSI sessions reached maximum limit log message. This
cannot be inferred as the maximum supported iSCSI sessions are reached. Also, number of iSCSI sessions displayed on the
system may show any number equal to or less than the maximum.
The following gure shows iSCSI optimization between servers in an M1000e enclosure and a storage array in which an Aggregator
connects installed servers (iSCSI initiators) to a storage array (iSCSI targets) in a SAN network. iSCSI optimization running on the
Aggregator is congured to use dot1p priority-queue assignments to ensure that iSCSI trac in these sessions receives priority treatment
when forwarded on Aggregator hardware.
Figure 16. iSCSI Optimization Example
Monitoring iSCSI Trac Flows
The switch snoops iSCSI session-establishment and termination packets by installing classier rules that trap iSCSI protocol packets to the
CPU for examination.
Devices that initiate iSCSI sessions usually use well-known TCP ports 3260 or 860 to contact targets. When you enable iSCSI optimization,
by default the switch identies IP packets to or from these ports as iSCSI trac.
iSCSI Optimization
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