White Papers

Figure 59. Example of iSCSI Optimization
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.
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).
iSCSI Optimization
437