DELL N3000 User Manual

Configuring iSCSI Optimization

On N4000 switches, when the iSCSI CoS mode is disabled, the DCBX iSCSI 

Application Priority TLV is not generated by the switch. In either case, if 

DCBX is enabled and ports are configured as auto-up or auto-down, the 

Application Priority TLVs received from the configuration source are proxied 

to the other ports and, on the N4000 series switches, the CoS policy for iSCSI 

received via DCBX is applied to iSCSI packets.
When iSCSI CoS mode is enabled, iSCSI login sessions up to the switch 

limits are tracked, and data packets for those sessions are given the configured 

CoS treatment. iSCSI sessions in excess of the switch limits are not given the 

configured CoS treament; therefore, it is not advisable to exceed the iSCSI 

session limit. Multiple connections within a session are counted against the 

session limit, even though they show in the session table as a single session.
In the switch, iSCSI connections are aged out using the session aging timer. If 

the connection has no detected data packets during the timeout period, the 

connection is deleted from the switch internal session table. When all 

connections associated with a session age out or disconnect, the session is 

deleted.
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 the highest VLAN priority tag or DSCP value 

mapped to the highest queue not used for stack management or voice VLAN. 

Use the classofservice dot1p-mapping command or the Quality of Service → 

Class of Service → Mapping Table Configuration page to configure the 

relevant Class of Service parameters for the queue in order to complete the 

setting.
You can configure whether iSCSI frames are remarked to contain the 

configured VLAN priority tag or IP DSCP when forwarded through the 

switch.

iSCSI Optimization borrows ACL lists from the global system pool. ACL lists 

allocated by iSCSI Optimization reduce the total number of ACLs available 

for use by the network operator. Enabling iSCSI Optimization uses one ACL 

list to monitor for iSCSI sessions. Each monitored iSCSI session utilizes two 

rules from additional ACL lists up to a maximum of two ACL lists. This 

means that the maximum number of ACL lists allocated by iSCSI is three.