Administrator Guide

The following illustration shows iSCSI optimization between servers and a storage array in which a stack of three switches
connect installed servers (iSCSI initiators) to a storage array (iSCSI targets) in a SAN network. iSCSI optimization running on
the master switch is configured to use dot1p priority-queue assignments to ensure that iSCSI traffic in these sessions receives
priority treatment when forwarded on stacked switch hardware.
Figure 50. iSCSI Optimization Example
Monitoring iSCSI Traffic Flows
The switch snoops iSCSI session-establishment and termination packets by installing classifier 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 identifies IP packets to or from these ports as iSCSI traffic.
You can configure the switch to monitor traffic for additional port numbers or a combination of port number and target IP
address, and you can remove the well-known port numbers from monitoring.
Application of Quality of Service to iSCSI Traffic Flows
You can configure iSCSI CoS mode. This mode controls whether CoS (dot1p priority) queue assignment and/or packet marking
is performed on iSCSI traffic.
When you enable iSCSI CoS mode, the CoS policy is applied to iSCSI traffic. When you disable iSCSI CoS mode, iSCSI sessions
and connections are still detected and displayed in the status tables, but no CoS policy is applied to iSCSI traffic.
iSCSI Optimization
395