Cisco DS-C9216I-K9, Руководство по настройке

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27-3
Cisco MDS 9000 Fabric Manager Switch Configuration Guide
OL-7753-01
Chapter 27 Configuring Traffic Management
Control Traffic
All switches support the following types of traffic:
• Control Traffic
•
DataTraffic
Control Traffic
The Cisco MDS 9000 Family supports QoS for internally and externally generated control traffic. Within
a switch, control traffic is sourced to the supervisor module and is treated as a high priority frame. A
high priority status provides absolute priority over all other traffic and is assigned in the following cases:
• Internally generated time-critical control traffic (mostly Class F frames).
•
Externally generated time-critical control traffic entering a switch in the Cisco MDS 9000 Family
from a another vendor switch. High priority frames originating from other vendor switches are
marked as high priority as they enter a switch in the Cisco MDS 9000 Family.
Disabling Control Traffic
By default, the QoS feature for certain critical control traffic is enabled. These critical control frames
are assigned the highest (absolute) priority.
We do not recommended disabling this feature as all critical control traffic will automatically be
assigned the lowest priority once you issue this command. You can view the current state of the QoS
configuration for critical control traffic using the
show qos statistics command.
Data Traffic
Transaction processing, a low volume, latency sensitive application, requires quick access to requested
information. Backup processing requires high bandwidth but is not sensitive to latency. In a network that
does not support service differentiation, all traffic is treated identically; they experience similar latency
and get similar bandwidths. The QoS feature in all switches in the Cisco MDS 9000 Family provides
these guarantees from SAN-OS Release 1.3(x).
Prior versions of the SAN-OS software only differentiated traffic priority based on control traffic.
SAN-OS Release 1.3(x) enables you to take full advantage of the QoS capabilities. Data traffic can now
be prioritized in four distinct levels of service differentiation: low, medium, high, or absolute priority.
You can apply QoS to ensure that Fibre Channel data traffic for your latency-sensitive applications
receive higher priority over throughput-intensive applications like data warehousing.