User's Manual

Configuration Guide of XGS-5240-Series
29-2
According to the characters (including field values like COS and DSCP) of upstream
packets, policing and rewriting of Egress make the last QoS change on the packet prior to the
packet egress.
Policing configures different policing policy based on the flow and distributes bandwidth
for the flow classified. The distribution policy of bandwidth can be either dual bucket dual color
or dual bucket three color. Different colors can be assigned to different flows and approaches
of discard or passage can be chosen for them; you can add rewriting action for packets with
passage approach chosen. See the following flow chart for detailed description of Egress QoS:
Classification
schedulingRemarkPolicing
Generate
internal
priority
Ingress Egress
color
Sort packet traffic
according to the
classification info and
convert classification info
to internal priority value
and drop precedence
value
Decide whether traffic
color is single bucket
dual color or dual
bucket three color
according policing
policy
Degrade or discard
different color packets,
and remark DSCP,
TOS, COS fields
Place packets into priority
queues according to
internal priority, provide
the service for them
according to queue weight
and drop precedence
Policing and
remark of
Egress
Set the color of packet
traffic according to policing
policy of Egress
PolicyMap, degrade or
drop different color
packets
End
Start
No
Drop
Pass
Yes
Select one or several following options:
Set COS: Set L2 COS field of packets
Set Drop/Transmit: Set drop or pass packets
Set DSCP/TOS: Set DSCP or TOS field of
packets
Whether configure
policing policy
Decide color and
action of packets
according to
policy
Specific color
action
Drop packets