Concept Guide

Monitoring iSCSI Trac Flows
The switch snoops iSCSI session-establishment and termination packets by installing classier 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 identies IP packets to or from these ports as iSCSI trac.
You can congure the switch to monitor trac 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 Trac Flows
You can congure iSCSI CoS mode. This mode controls whether CoS (dot1p priority) queue assignment and/or packet marking is
performed on iSCSI trac.
When you enable iSCSI CoS mode, the CoS policy is applied to iSCSI trac. 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 trac.
You can congure whether the iSCSI optimization feature uses the VLAN priority or IP DSCP mapping to determine the trac class queue.
By default, iSCSI ows are assigned to dot1p priority 4. To map incoming iSCSI trac on an interface to a dot1p priority-queue other than 4,
use the
QoS dot1p-priority command (refer to QoS dot1p Trac Classication and Queue Assignment). Dell EMC Networking
recommends setting the CoS dot1p priority-queue to 0 (zero).
You can congure whether iSCSI frames are re-marked to contain the congured VLAN priority tag or IP DSCP when forwarded through
the switch.
NOTE
: On a switch in which a large proportion of trac is iSCSI, CoS queue assignments may interfere with other network
control-plane trac, such as ARP or LACP. Balance preferential treatment of iSCSI trac against the needs of other critical
data in the network.
Information Monitored in iSCSI Trac Flows
iSCSI optimization examines the following data in packets and uses the data to track the session and create the classier entries that
enable QoS treatment.
• Initiator’s IP Address
• Target’s IP Address
• ISID (Initiator dened session identier)
• Initiator’s IQN (iSCSI qualied name)
• Target’s IQN
• Initiator’s TCP Port
• Target’s TCP Port
• Connection ID
• Aging
• Up Time
If no iSCSI trac is detected for a session during a user-congurable aging period, the session data is cleared.
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iSCSI Optimization