User manual

C HAPTER 11 | Class of Service
Layer 3/4 Priority Settings
– 136 –
ES-2000 Series
MAPPING COS
PRIORITIES TO
INTERNAL DSCP
V
ALUES
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.
COMMAND USAGE
◆ The default mapping of CoS to PHB values is shown in Table 16 on
page 137.
◆ 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.
PARAMETERS
These parameters are displayed:
◆ CoS – CoS value in ingress packets. (Range: 0-7)
◆ CFI – Canonical Format Indicator. Set to this parameter to “0” to
indicate that the MAC address information carried in the frame is in
canonical format. (Range: 0-1)
◆ 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)