Configuration Guide User guide

1970 FastIron Configuration Guide
53-1002494-02
QoS for Brocade stackable devices
Mapping between the DSCP value and forwarding queue cannot be changed. However, mapping
between DSCP values and other properties can be changed as follows:
• DSCP to internal forwarding priority mapping – You can change the mapping between the
DSCP value and the internal forwarding priority value from the default values shown in
Table 329 through Table 332. This mapping is used for CoS marking and determining the
internal priority when the trust level is DSCP. Refer to “Changing the DSCP to internal
forwarding priority mappings” on page 1984.
• VLAN priority (802.1p) to hardware forwarding queue - You can change the mapping between
the 802.1p value and hardware forwarding queue from the default value. Refer to “Changing
the VLAN priority 802.1p to hardware forwarding queue mappings” on page 1985.
QoS for Brocade stackable devices
Brocade FastIron units in an IronStack support QoS. Units in a stack communicate the stack
topology information and other proprietary control information through the stacking links. For more
information about stacking links and IronStack technology, refer to Chapter 7, “Brocade Stackable
Devices”.
In addition to control information, the stacking links also carry user network data packets. In an
IronStack topology, the priority of stacking-specific control packets is elevated above that of data
path packets, preventing loss of control packets, and timed retries that affect performance. This
prioritization also prevents stack topology changes that may occur if enough stack topology
information packets are lost.
IronStack technology reserves one QoS profile to provide a higher priority for stack topology and
control traffic.
QoS profile restrictions in an IronStack
In a stacking topology, because CoS level 7 is reserved for stacking, quality profiles for qosp7
cannot be configured. If an attempt is made to configure a profile for qosp7, the system ignores the
configuration.
NOTE
This applies only when the device is operating in stacking mode. It does not apply to stand-alone
devices.
TABLE 332 Default QoS mappings for FCX platforms, columns 48 to 63
DSCP value 48495051525354555657585960616263
802.1p (CoS)
value
6666666677777777
DSCP value 48495051525354555657585960616263
Internal
forwarding
priority
6666666677777777
Forwarding
queue
6666666677777777