Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 398

CS_CTL-based frame prioritization, Supported configurations for CS_CTL-based frame prioritization

Page 398 highlights

Optimizing Fabric Behavior ∙ QoS zones that use D,I notation should not be used for loop or NPIV ports. ∙ If QoS is enabled, an additional 16 buffer credits are allocated per port for 8-Gbps ports in Extended Mode (LE). Refer to Managing Long-Distance Fabrics on page 483 for information about buffer credit allocation in extended fabrics. ∙ If some ports in a trunk group have QoS enabled and some ports have QoS disabled, then two different trunks are formed, one with QoS enabled and one with QoS disabled. ∙ QoS mode cannot be explicitly enabled on simulation ports (SIM ports). CS_CTL mode can be enabled on SIM ports. 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 76. The values are enabled by default to ensure backward compatibility. TABLE 76 Mapping of CS_CTL values to QoS priority for frame prioritization in CS_CTL default mode CS_CTL value Priority 1-8 Low 9-16 17-24 Medium High Alternatively, the user can apply CS_CTL auto mode. The CS_CTL auto mode uses only three CS_CTL values, as illustrated in Table 77. TABLE 77 Mapping of CS_CTL values to QoS priority for frame prioritization in CS_CTL auto mode CS_CTL value Priority 1 Low 2 Medium 3 High NOTE The values in the tables represent chassis-level configurations. For configuration details, refer to Using CS_CTL auto mode at the chassis level on page 399, and Considerations for using CS_CTL-based frame prioritization on page 400. Supported configurations for CS_CTL-based frame prioritization CS_CTL-based frame prioritization is supported on all 8-, 16-, and 32-Gbps platforms. All switches in the fabric should be running Fabric OS v6.3.0 or later. Brocade Fabric OS Administration Guide, 8.0.1 398 53-1004111-02

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QoS zones that use D,I notation should not be used for loop or NPIV ports.
If QoS is enabled, an additional 16 buffer credits are allocated per port for 8-Gbps ports in Extended Mode (LE). Refer to
Managing Long-Distance Fabrics
on page 483 for information about buffer credit allocation in extended fabrics.
If some ports in a trunk group have QoS enabled and some ports have QoS disabled, then two different trunks are formed, one
with QoS enabled and one with QoS disabled.
QoS mode cannot be explicitly enabled on simulation ports (SIM ports). CS_CTL mode can be enabled on SIM ports.
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 76
. The values are enabled by default to ensure backward compatibility.
TABLE 76
Mapping of CS_CTL values to QoS priority for frame prioritization in CS_CTL default mode
CS_CTL value
Priority
1-8
Low
9-16
Medium
17-24
High
Alternatively, the user can apply CS_CTL auto mode. The CS_CTL auto mode uses only three CS_CTL values, as illustrated in
Table 77
.
TABLE 77
Mapping of CS_CTL values to QoS priority for frame prioritization in CS_CTL auto mode
CS_CTL value
Priority
1
Low
2
Medium
3
High
NOTE
The values in the tables represent chassis-level configurations. For configuration details, refer to
Using CS_CTL auto mode at
the chassis level
on page 399, and
Considerations for using CS_CTL-based frame prioritization
on page 400.
Supported configurations for CS_CTL-based frame prioritization
CS_CTL-based frame prioritization is supported on all 8-, 16-, and 32-Gbps platforms.
All switches in the fabric should be running Fabric OS v6.3.0 or later.
Optimizing Fabric Behavior
Brocade Fabric OS Administration Guide, 8.0.1
398
53-1004111-02