Finally, we evaluate the impact of transmission loss on the response time for the different protocols. We consider transmissions with an average RTT of 25 ms and subject the packets to a constant loss rate, independent of the load in the system. Figure 11 graphs the results. The response time for TCP blows up with increased loss rates, since TCP interprets losses as signals of congestion. PCP and fair queueing can tolerate losses without suffering a substantial increase in response times. In PCP, when a loss is detected, either through a timeout or by the presence of acknowledgments for subsequent messages, the packet is scheduled for retransmission for the next available time slot based on the current paced transmission rate.
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