ECS3510-26P_Management Guide R02

C HAPTER 34 | Class of Service Commands
Priority Commands (Layer 3 and 4)
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DEFAULT SETTING.
COMMAND MODE
Interface Configuration (Port, Static Aggregation)
COMMAND USAGE
◆ The default mapping of CoS to PHB values shown in Table 122 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.
◆ RED starts dropping yellow and red packets when the buffer fills up to
16 packets on ports 1-48 and 72 packets on ports 49-50/52, and then
starts dropping any packets regardless of color when the buffer fills up
to 58 packets on ports 1-48 and 80 packets on ports 49-50/52.
◆ 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)#
Table 122: Default Mapping of CoS/CFI to Internal PHB/Drop Precedence
CFI
CoS
0 1
0 (0,0) (0,0)
1 (1,0) (1,0)
2 (2,0) (2,0)
3 (3,0) (3,0)
4 (4,0) (4,0)
5 (5,0) (5,0)
6 (6,0) (6,0)
7 (7,0) (7,0)