Brocade 6910 Ethernet Access Switch Configuration Guide (Supporting R2.2.0.0) - Manual (Page 477)

Brocade 6910 Ethernet Access Switch Configuration Guide 421
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Priority Commands (Layer 3 and 4)
Command Usage
• The default mapping of CoS to PHB values shown in Table 99 is based on the recommended
settings in IEEE 802.1p for mapping CoS values to output queues.
• Enter a value pair for the internal per-hop behavior and drop precedence, followed by the
keyword “from” and then up to eight CoS/CFI paired values separated by spaces.
• If a packet arrives with a 802.1Q header but it is not an IP packet, then the
CoS/CFI-to-PHB/Drop Precedence mapping table is used to generate priority and drop
precedence values for internal processing. Note that priority tags in the original packet are not
modified by this command.
• The internal DSCP consists of three bits for per-hop behavior (PHB) which determines the
queue to which a packet is sent; and two bits for drop precedence (namely color) which is used
by Random Early Detection (RED) to control traffic congestion.
• Random Early Detection starts dropping yellow and red packets when the buffer fills up to 16
packets on a port, and then starts dropping any packets regardless of color when the buffer
fills up to 58 packets on a port.
• The specified mapping applies to all interfaces.
Example
Console(config)#interface ethernet 1/5
Console(config-if)#qos map cos-dscp 0 0 from 0 1
Console(config-if)#
qos map dscp-mutation
This command maps DSCP values in incoming packets to per-hop behavior and drop precedence
values for priority processing. Use the no form to restore the default settings.
Syntax
qos map dscp-mutation phb drop-precedence from dscp0 ... dscp7
no qos map dscp-mutation dscp0 ... dscp7
phb - Per-hop behavior, or the priority used for this router hop. (Range: 0-7)
drop-precedence - Drop precedence used for Random Early Detection in controlling traffic
congestion.
(Range: 0 - Green, 3 - Yellow, 1 - Red)
dscp - DSCP value in ingress packets. (Range: 0-63)