C
HAPTER
10
| Class of Service
Layer 3/4 Priority Settings
– 280 –
â—† This map is only used when the priority mapping mode is set to DSCP
(see page 278), and the ingress packet type is IPv4. Any attempt to
configure the DSCP mutation map will not be accepted by the switch,
unless the trust mode has been set to DSCP.
â—† 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.
â—† 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.
PARAMETERS
These parameters are displayed:
◆ Port – Specifies a port.
◆ DSCP – DSCP value in ingress packets. (Range: 0-63)
◆ 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)
Table 17: 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
6 7,0 7,1 7,0 7,3
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.
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