Fabric OS Administrator's Guide v7.0.0 (53-1002148-02, June 2011)

Fabric OS Administrator’s Guide 413
53-1002148-02
QoS: SID/DID traffic prioritization
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Virtual Fabrics considerations: If Virtual Fabrics is enabled, the rate limit configuration on a port is
on a per-logical switch basis. That is, if a port is configured to have a certain rate limit value, and
the port is then moved to a different logical switch, it would have no rate limit applied to it in the
new logical switch. If that same port is moved back to the original logical switch, it would have the
original rate limit take effect again.
Limiting traffic from a particular device
1. Connect to the switch and log in as admin.
2. Enter the portCfgQos
--setratelimit command.
portcfgqos --setratelimit slot/port ratelimit
Example of setting the rate limit on slot 3, port 9 to 4000 Mbps
portcfgqos --setratelimit 3/9 4000
Disabling ingress rate limiting
1. Connect to the switch and log in as admin.
2. Enter the portCfgQos
--resetratelimit command.
portcfgqos --resetratelimit slot/port
Example of disabling ingress rate limiting on slot 3, port 9
portcfgqos --resetratelimit 3/9
QoS: SID/DID traffic prioritization
SID/DID traffic prioritization allows you to categorize the traffic flow between a host and target as
having a high, medium, or low priority. Fabric OS supports two types of prioritization:
• Class Specific Control (CS_CTL)-based frame prioritization
Each frame between a host and a target is assigned a specific priority, depending on the value
of the CS_CTL field in the frame header.
• QoS zone-based traffic prioritization
All traffic between a host and a target is assigned a specific priority, depending on the name
you define for the QoS zone.
CS_CTL-based prioritization and QoS zone-based prioritization are mutually exclusive. If you enable
CS_CTL-based prioritization on F/FL_Ports, then QoS zone-based prioritization cannot be used
between any devices connected to those F/FL_Ports.
CS_CTL-based prioritization takes precedence over QoS zone-based prioritization. If you enable
CS_CTL-based prioritization on F/FL_Ports that are defined in a QoS zone, CS_CTL-based
prioritization takes precedence over the QoS zones.
Table 72 shows a basic comparison between CS-CTL-based and QoS zone-based prioritization. See
“CS_CTL-based frame prioritization” on page 414 and “QoS zone-based traffic prioritization” on
page 415 for detailed information about each type of prioritization scheme.