User guide

426 Brocade 6910 Ethernet Access Switch Configuration Guide
53-1002581-01
Priority Commands (Layer 3 and 4)
21
DEFAULT SETTING
Command Mode
Interface Configuration (Port)
Command Usage
• Enter a value pair for the internal per-hop behavior and drop precedence, followed by the
keyword “from” and then up to eight DSCP values separated by spaces.
• This map is only used when the QoS mapping mode is set to “DSCP” by the qos map
trust-mode command, and the ingress packet type is IPv4.
• Two QoS domains can have different DSCP definitions, so the DSCP-to-PHB/Drop Precedence
mutation map can be used to modify one set of DSCP values to match the definition of another
domain. The mutation map should be applied at the receiving port (ingress mutation) at the
boundary of a QoS administrative domain.
• Random Early Detection starts dropping yellow and red packets when the buffer fills up to
0x60 packets, and then starts dropping any packets regardless of color when the buffer fills up
to 0x80 packets.
• The specified mapping applies to all interfaces.
Example
This example changes the priority for all packets entering port 1 which contain a DSCP value of 1 to
a per-hop behavior of 3 and a drop precedence of 1. Referring to Table 100, note that the DSCP
value for these packets is now set to 25 (3x2
3
+1) and passed on to the egress interface.
Console(config)#interface ethernet 1/5
Console(config-if)#qos map dscp-mutation 3 1 from 1
Console(config-if)#
TABLE 100 Default Mapping of DSCP Values to Internal PHB/Drop Values
ingress-
dscp1
ingress-
dscp10
0123456789
0 0,0 0,1 0,0 0,3 0,0 0,1 0,0 0,3 1,0 1,1
1 1,0 1,3 1,0 1,1 1,0 1,3 2,0 2,1 2,0 2,3
2 2,0 2,1 2,0 2,3 3,0 3,1 3,0 3,3 3.0 3,1
3 3,0 3,3 4,0 4,1 4,0 4,3 4,0 4,1 4.0 4,3
4 5,0 5,1 5,0 5,3 5,0 5,1 6,0 5,3 6,0 6,1
5 6,0 6,3 6,0 6,1 6,0 6,3 7,0 7,1 7.0 7,3
67,07,17,07,3
The ingress DSCP is composed of ingress-dscp10 (most significant digit in the left column) and ingress-dscp1
(least significant digit in the top row (in other words, ingress-dscp = ingress-dscp10 * 10 + ingress-dscp1); and
the corresponding internal-dscp is shown at the intersecting cell in the table.
The ingress DSCP is bitwise ANDed with the binary value 11 to determine the drop precedence. If the resulting
value is 10 binary, then the drop precedence is set to 0.