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Architecture

Flows from a customer end point enter a DS domain through the Edge Router. So, the architecture at the edge router has provision for setting the DSCP and also for policing the packets. The architecture is as shown in the figure.

 Figure 1: Edge Router Architecture


 


The first level queue in the architecture is the ds_mark queuing discipline, which will be directly associated with the output device. The ds_mark queuing discipline sets the DSCP to the required codepoint.

From the ds_mark queuing discipline a u32 filter is created. The u32 filters are created for a particular flow. Each flow can be uniquely identified by the four tuple <src ip, dst ip, src port, dst port> or the three tuple <src ip, dst ip, dst port>. Each filter is associated with a meter which polices the flow for in profile and out of profile packets. A in profile EF flow's DSCP is marked with 0x2e and the out of profile packets are dropped. In AF the in profile packets are marked with the assigned codepoint and the out of profile packets are reclassified as best effort.

The packets emerging out of the Edge Router have their DSCPs marked and are also policed according to the bandwidth allocated to the customer by the Bandwidth Broker.


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Anupama Sundaresan

1999-12-19