ECS3510-26P_Management Guide R02

C HAPTER 10 | Class of Service
Layer 3/4 Priority Settings
– 249 –
To show the DSCP to internal PHB/drop precedence map:
1. Click Traffic, Priority, DSCP to DSCP.
2. Select Show from the Action list.
Figure 121: Showing DSCP to DSCP Internal Mapping
MAPPING COS
PRIORITIES TO
INTERNAL DSCP
VALUES
Use the Traffic > Priority > CoS to DSCP page to maps CoS/CFI values in
incoming packets to per-hop behavior and drop precedence values for
priority processing.
CLI REFERENCES
◆ "qos map cos-dscp" on page 862
COMMAND USAGE
◆ The default mapping of CoS to PHB values is shown in Table 18 on
page 250.
◆ Enter up to eight CoS/CFI paired values, per-hop behavior and drop
precedence.
◆ 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 Fast Ethernet ports and 72 packets on Gigabit Ethernet
ports, and then starts dropping any packets regardless of color when
the buffer fills up to 58 packets on Fast Ethernet ports and 80 packets
on Gigabit Ethernet ports.
◆ The specified mapping applies to all interfaces.