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Chapter 6
Meters, queues and IPQoS
E-NIT-CTC-20041213-0013 v0.5
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6.4.2 Packet flow
Illustration The figure below illustrates the packet flow in case label based metering is used.
Stage Description
1 A packet arrives in the resource management module and gets
classified based upon a rule set. The packet gets a label assigned.
In case the label refers to a meter the packet gets forwarded to the
meter module. If not, the packet is forwarded back to the LAN or to
the WAN after queuing and scheduling.
2 Packets in excess of the drop rate will be dropped or counted
depending on the settings of the dropaction parameter.
3 If the mark rate is exceeded the packet will be marked or counted
depending on the settings of the markaction parameter. If a packet is
marked, the tos byte can be set or the internal class can be changed.
If classification has been enabled the internal class will be set.
4 The class is set. This will place packets in a specified queue.
5 Based upon the destination (LAN/WAN) the packet gets forwarded to
the proper interface.
6 In case the packet will be sent out to the WAN side, the packet gets
assigned to the corresponding queue.
7 Finally the ATMQoS parameters are taken into account and the
packet is ready to be sent to the WAN.
Packet
Data
MeterClassification Meter
Drop
Packet is
dropped
Mark Tos marking Set tos byte
Classification
Set Class
Action
Action
Queue
scheduling
Map class to
queue
ATM QoS
1
2
3
4
5
6
Drop
Count
Count
Mark
yes
no
no
no
yes
yes yes
no
no
yes
LAN
7
WAN
Classification
Metering