Fleksibilni Internet servisi na bazi kontrole kašnjenja i

sensitive flows into two different queues and assignees service rates to these queues that
will ensure that the ratio of average queuing delays for throughput-sensitive and delay-
sensitive classes is equal to the ratio specified by a network operator. In Section 5, we
present an ideal rate assignment strategy for proportional delay differentiation named
Optimized BPR (BPR + ) in order to evaluate the performance of BPR scheduler. BPR +
[38] is an extension of BPR. It employs more complete information about backlogged
traffic to assign service rates to TS and DS queues in order to more precisely approximate
the specified delay ratio δ. Even though BPR + is to complex to warrant practical
implementations, it is useful as a benchmark for evaluating other possible rate assignment
strategies for proportional delay differentiation. Detailed description and performance
comparison of BPR + and BPR is given in Section 5.
The second objective is accomplished using a new algorithm, named Packet Loss
Controller (PLC). Since BPR scheduler is work-conserving, average queuing delay is
identical as in the case of FCFS scheduling employed in a best-effort network. If the total
number of packets accepted in the buffer is maintained to be the same as it would be in a
best-effort network, lower delay for delay-sensitive packets can be achieved only by
increasing the queuing delay for throughput-sensitive packets. Since throughput of a TCP
flow depends on its round-trip time, introduction of low-delay service for delay-sensitive
class will deteriorate the performance of throughput-sensitive applications that use TCP
as a transport protocol. The PLC controller is used to overcome this problem by
protecting the throughput of TCP flows. It guarantees that the TCP throughput in the
presence of delay differentiation is not lower than in a best-effort network. PLC
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