Application Of Quality Of Service To Iscsi Traffic Flows; Information Monitored In Iscsi Traffic Flows - Dell S4048T Configuration Manual

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 QoS dot1p-priority command
(refer to QoS dot1p Traffic Classification and Queue
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.

Information Monitored in iSCSI Traffic Flows

iSCSI optimization examines the following data in packets and uses the data to track the session and create
the classifier entries that enable 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 Time
If no iSCSI traffic is detected for a session during a user-configurable aging period, the session data is cleared.
If more than 256 simultaneous sessions are logged continuously, the following message displays indicating
the queue rate limit has been reached:
%STKUNIT2-M:CP %iSCSI-5-ISCSI_OPT_MAX_SESS_EXCEEDED: New iSCSI Session Ignored:
ISID -
Assignment). Dell Networking recommends setting the
iSCSI Optimization 545