Cs_ctl-based frame prioritization, Table 77, Table 78 – Dell POWEREDGE M1000E User Manual

Page 521

Fabric OS Administrator’s Guide

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CS_CTL-based frame prioritization

CS_CTL-based frame prioritization allows you to prioritize the frames between a host and target as
having high, medium, or low priority, depending on the value of the CS_CTL field in the FC frame
header.

The CS_CTL field in the FC header can be used to assign a priority to a frame. This field can be
populated by selected end devices (storage or hosts) and then honored by the switch, which
assigns the frame, based on the value in the CS_CTL field, to allocate appropriate resources
throughout the fabric. This method of establishing QoS is an alternative to the switch-controlled
assignment that uses zone-based QoS.

ATTENTION

Check with your host and storage manufacturer to determine whether they support Fibre Channel
CS_CTL prioritization on their devices.

High-, medium-, and low-priority frames are allocated to different sets of fabric resources.
High-priority frames are assigned to more fabric resources than are medium-priority frames, which
in turn are assigned to more fabric resources than are low-priority frames. The resources are
allocated according to the CS_CTL value, as shown in

Table 77

. The values are enabled by default

to ensure backward compatibility.

Alternatively, the user can apply CS_CTL auto mode. The CS_CTL auto mode uses only three
CS_CTL values, as illustrated in

Table 78

NOTE

The values in the tables above represent chassis-level configurations. For configuration details, see

“Using CS_CTL auto mode at the chassis level”

on page 522, and

“Considerations for using

CS_CTL-based frame prioritization”

on page 523.