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4-13
Data Center High Availability Clusters Design Guide
OL-12518-01
Chapter 4 FCIP over IP/MPLS Core
QoS Requirements in FCIP
QoS Requirements in FCIP
Currently, most of the FCIP links are dedicated for pure Fibre Channel traffic. But in most cases if QoS
is enabled, most of the SAN applications can be transported across the same traffic engineered
infrastructure shared with traditional IP traffic. Because there are several QoS models, make sure the
right Differentiated Services Code Point (DSCP) is applied to get the assumed results.
To ensure that one QoS model does not conflict with another application (that is, they can run on the
same network), it is important for a common set of QoS priority markings to be used across the entire
SP network that is in agreement with enterprise traffic. Following is a recommended set of class of
service (COS) and MPLS EXP encodings for a typical application:
• 0—Best effort
• 1—Peak information rate (PIR)
• 2—Committed information rate (CIR)/priority
• 3—Cisco AVVID call control
• 4—FCIP (this is just a recommendation; a full analysis of the network and application is required)
• 5—Voice transport
• 6—Video
• 7—SP network management and control
Note The above DSCP values are just a recommendation; a network administrator may choose another
consistent set of numbers if desired.
Cisco MDS supports DSCP values for marking all IP packets in the type of service (TOS) field in the IP
header. You can specify different values for control and data:
• The control DSCP value applies to all FCIP frames in the control TCP connection.
• The data DSCP value applies to all FCIP frames in the data connection.
If the FCIP link has only one TCP connection, that data DSCP value is applied to all packets in that link.
The following command configures the control TCP connection and data connection to mark all packets
on that DSCP value.
switch(config-profile)# tcp qos control 4 data 5
The following command reverts the switch to its factory default:
switch(config-profile)# no tcp qos control 4 data 5
QoS can also be applied using the Fabric Manager/Device Manager GUI. Figure 4-4 shows a QoS value
of 3 applied to Control and a value of 5 applied to Data using the management GUI.