There may be times when a network operator wants to provide differentiated service to specific traffic flows within its network, and these traffic flows can be identified with known routes. For example, the operator of an ISP network may want to give priority to traffic originating in a particular ASN (the ASN of a content provider offering over-the-top services to the ISP’s customers), following a specific AS_PATH, or destined for a particular next-hop (remaining on-net vs. off-net).
Figure: Use of QPPB to differentiate traffic in an ISP network shows an example of an ISP that has an agreement with the content provider managing AS300 to provide traffic sourced and terminating within AS300 with differentiated service appropriate to the content being transported. In this example, we presume that ASBR1 and ASBR2 mark the DSCP of packets terminating and sourced, respectively, in AS300 so that other nodes within the ISP’s network do not need to rely on QPPB to determine the correct forwarding-class to use for the traffic. The DSCP or other CoS markings could be left unchanged in the ISP’s network and QPPB used on every node.
