Administrator Guide

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.
You can configure whether the iSCSI optimization feature uses the VLAN priority or IP DSCP mapping to determine the traffic
class queue. By default, iSCSI flows are assigned to dot1p priority 4. To map incoming iSCSI traffic on an interface to a dot1p
priority-queue other than 4, use the CoS dot1p-priority command (refer to QoS dot1p Traffic Classification and Queue
Assignment). Dell Networking recommends setting the CoS dot1p priority-queue to 0 (zero).
You can configure whether iSCSI frames are re-marked to contain the configured VLAN priority tag or IP DSCP when forwarded
through the switch.
NOTE: On a switch in which a large proportion of traffic is iSCSI, CoS queue assignments may interfere with other network
control-plane traffic, such as ARP or LACP. Balance preferential treatment of iSCSI traffic against the needs of other
critical data in the network.
516 iSCSI Optimization