Configuring iSCSI Optimization 391How Does iSCSI Optimization Interact with DCBx?The Data Center Bridging Exchange (DCBx) component supports thereception, decoding, and transmission of the Application Priority TLV. Ingeneral, if the Application Priority TLV has been received from theconfiguration source, it will be transmitted to the other auto configurationports. The DCBx component contains a control to generate the ApplicationPriority TLV for iSCSI if it is not already present in the DCBX information.DCBx generates an Application Priority TLV whenever the followingconditions are met:• An EqualLogic array has been detected on the port• iSCSI CoS is enabled using a VPT valueThe generated Application Priority TLV will contain the following values (inaddition to any other information contained in the TLV):• AE Selector=14• AE Protocol=3260• AE Priority=priority configured for iSCSI PFC by the iscsi cos vptcommand (default priority is 4)The existing application priority entries being transmitted, if any, will not bedisturbed.How Does iSCSI Optimization Interact with Dell Compellent Arrays?Dell PowerConnect switches support a macro that may be used to configure aport connected to a Dell Compellent storage array. The name of the macro isprofile-compellent-nas. The macro takes a single argument: theinterface identifier to which the Dell Compellent array is connected. Themacro disables unicast storm control and sets the spanning tree configurationon the port to portfast. For an example of how to execute the macro, see"Configuring iSCSI Optimization Between Servers and a Disk Array" onpage 399.NOTE: If it is desired to utilize DCBX to configure lossless transport of iSCSI usingPFC, the operator MUST configure a VLAN end-to-end in order to transport theVLAN priority tag and ensure proper COS treatment on every network enableddevice, including CNAs and the EQL arrays.
