Deployment Guide

Comparison between CS_CTL-based and QoS zone-based prioritization (Continued)TABLE 74
CS_CTL-based frame prioritization QoS zone-based traffic prioritization
Setup steps:
• Enable CS_CTL mode on F_Ports or FL_Ports.
• Ensure that the CS_CTL mode-enabled host and storage
are zoned together.
Setup steps:
• Create QoS zones with host/target members.
• Add the QoS zones to the zone configuration.
• Save and then enable the zone configuration.
• Enable QoS on E_Ports.
License requirements for QoS
Starting in Fabric OS 7.2.0, QoS does not require the Adaptive Networking license to be explicitly
installed. This license is automatically enabled for new switches and for existing switches that are
upgraded to Fabric OS 7.2.0 or later.
If you upgrade to Fabric OS 7.2.0 and you did not previously have an Adaptive Networking license,
then all ports that had QoS mode set to AE (automatically enabled) and were not using the QoS
feature are automatically set to OFF after the upgrade.
CS_CTL-based frame prioritization
CS_CTL-based frame prioritization allows you to prioritize the frames between a host and a 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 and host) 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 manufacturers 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 more fabric resources than medium-priority frames, which in turn are assigned
more fabric resources than low-priority frames. The resources are allocated according to the CS_CTL
value, as shown in Table 75 . The values are enabled by default to ensure backward compatibility.
Mapping of CS_CTL values to QoS priority for frame prioritization in CS_CTL default
mode
TABLE 75
CS_CTL value Priority
1-8 Low
9-16 Medium
License requirements for QoS
378 Fabric OS Administrators Guide
53-1003130-01