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IADIS International Conference WWW/Internet 2010A main characteristic that distinguishes a VoIP sender of a CBR sender is not occupying the link all thetime, due to silence periods. Hence, different protocols have different responses to this variation. Table 1presents CUBIC versus DCCP CCID 2, with VoIP traffic. DCCP CCID2 achieves better average throughputand delivery rate, with less dropped packets. As the congestion control of CUBIC is more aggressive, it isexpected that CUBIC achieve better throughput values. However, with VoIP traffic CUBIC suffers with theconstant interruptions in the packet generation, due to the poor growth of the W _ max , forcing the major useof the convex (i.e., slow) part of the growing cubic function. As a result, the opponent protocol can grab abigger share of link bandwidth. Average delay differences are negligible (i.e., 6 % ).Table 1. CUBIC versus DCCP CCID2 with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)CUBIC 90.76 (0.00) 21892.20 (105.01) 2015.24 (55.88) 28.26 (0.15) 0.48 (0.00)DCCP CCID2 98.19 (0.00) 21372.10 (105.67) 379.69 (5.26) 29.85 (0.15) 0.50 (0.00)Similarly, in this scenario, CTCP outperforms CUBIC, as shown in Table 2:Table 2. CUBIC versus Compound TCP with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)CUBIC 91.22 (0.00) 19966.50 (186.72) 1748.96 (44.02) 25.91 (0.22) 0.46 (0.00)CTCP 97.12 (0.00) 20638.80 (143.09) 573.55 (8.18) 28.53 (0.20) 0.49 (0.00)As shown in Table 3 and Table 4, when using VoIP traffic, DCCP CCID2 outperforms CTCP and DCCPCCID3. DCCP CCID2 achieves better average throughput, delivery rate, and dropping less packets. Averagedelay differences are negligible (i.e., ≈ 6%).Table 3. Compound TCP versus DCCP CCID2 with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)CTCP 95.11 (0.00) 19467.70 (144.10) 919.43 (12.22) 26.37 (0.21) 0.46 (0.00)DCCP CCID2 98.70 (0.00) 21608.80 (199.82) 277.87 (4.02) 30.33 (0.28) 0.47 (0.00)Table 4. DCCP CCID2 versus DCCP CCID3 with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)DCCP CCID2 99.98 (0.00) 21807.90 (80.80) 2.51 (0.42) 31.01 (0.12) 0.12 (0.00)DCCP CCID3 99.89 (0.00) 7698.68 (376.15) 0.37 (0.06) 10.95 (0.54) 0.12 (0.00)In simulations with DCCP CCID3 there are low delay values and low dropped packets, independently ofthe opponent protocol. This fact is due to the very precise CCID3 congestion control mechanism, where tothe slightest sign of congestion, a rigorous reduction of the sending rate is performed. As a result, theopponent protocol may expand its share of the link bandwidth, and the fair equilibrium is never reached. Thisis clear also in Table 5 and Table 6, where DCCP CCID3 is compared to CTCP and CUBIC, respectively.Table 5. Compound TCP versus DCCP CCID3 with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)CTCP 99.97 (0.00) 21878.70 (143.95) 5.21 (1.00) 31.11 (0.20) 0.13 (0.00)DCCP CCID3 99.89 (0.00) 7391.94 (207.49) 0.33 (0.04) 10.51 (0.30) 0.12 (0.00)Table 6. CUBIC versus DCCP CCID3 with VoIP TrafficDelivery Rate(%)Sent Packets(packets)Dropped Packets(packets)Average Throughput(Kbps)Average End toEnd Delay (s)CUBIC 99.96 (0.00) 21910.50 (148.36) 6.49 (1.08) 31.15 (0.21) 0.13 (0.00)DCCP CCID3 99.89 (0.00) 6635.50 (259.73) 0.42 (0.04) 9.44 (0.37) 0.12 (0.00)215