Monitoring iSCSI Traffic FlowsThe switch snoops iSCSI session-establishment and termination packets by installing classifier rules that trap iSCSI protocol packets to theCPU 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 youcan remove the well-known port numbers from monitoring.Application of Quality of Service to iSCSI Traffic FlowsYou can configure iSCSI CoS mode. This mode controls whether CoS (dot1p priority) queue assignment and/or packet marking isperformed 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 andconnections 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 QoS dot1p-priority command (refer to QoS dot1p Traffic Classification and Queue Assignment). Dell Networkingrecommends 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 throughthe switch.NOTE: On a switch in which a large proportion of traffic is iSCSI, CoS queue assignments may interfere with other networkcontrol-plane traffic, such as ARP or LACP. Balance preferential treatment of iSCSI traffic against the needs of other critical datain the network.Information Monitored in iSCSI Traffic FlowsiSCSI optimization examines the following data in packets and uses the data to track the session and create the classifier entries thatenable QoS treatment.• Initiator’s IP Address• Target’s IP Address• ISID (Initiator defined session identifier)• Initiator’s IQN (iSCSI qualified name)• Target’s IQN• Initiator’s TCP Port• Target’s TCP Port• Connection ID• Aging• Up TimeIf no iSCSI traffic is detected for a session during a user-configurable aging period, the session data is cleared.iSCSI Optimization 473
