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ISBN: 978-972-8939-25-0 © 2010 IADIS3.2.1 CBR Traffic PatternIn the CBR scenarios, DCCP CCID2 has achieved good results when compared with protocols with moreresponsive and accurate congestion control, like DCCP CCID3 and CTCP, which reduce their sending ratesat the slightest sign of congestion. As shown in Figure 2, sender 37 (DCCP CCID3) has suffered with thecongestion, reducing its sending rate. Also, one may note a slow resumption of throughput, due to aconservative increase function in DCCP CCID3. However, in simulations with DCCP CCID3, sender nodeshave demonstrated high throughput stability, low delay and all the transmissions have fewer dropped packets,due to the rigorous congestion control. In contrast, it is possible to see in Figure 3 many oscillations in theinstant throughput, what denotes a low stability of the congestion control of CTCP when fighting with DCCPCCID2 in a network scenario with contention. Also, the congestion controls of both protocols are moreaggressive than DCCP CCID3, what is evidenced with sender25 (DCCP CCID2) in the time interval of 180s-220s and with sender13 (CTCP) in time interval of 20s-110s.Figure 2. Instant throughput.Figure 3. Instant throughput.Table 7, Table 8 and Table 9 present results showing that DCCP CCID2 has achieved better throughputthan DCCP CCID3 and CTCP, but with worse stability (see Figure 2 and Figure 3), and longer delay thanDCCP CCID3. In addition to that, CTCP has dropped more packets, achieving lower throughput than DCCPCCID2.Table 7. DCCP CCID2 versus DCCP CCID3 with CBR TrafficDelivery Rate (%) Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd DelayDCCP CCID2 99.84 (0.00) 53694.30 (1654.49) 28.70 (11.86) 476.50 (14.72) 0.18 (0.01)DCCP CCID3 99.86 (0.00) 40449.00 (2813.26) 6.45 (1.79) 358.94 (25.03) 0.19 (0.01)Table 8. Compound TCP versus DCCP CCID2 with CBR TrafficDelivery Rate (%) Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)DCCP CCID2 99.75 (0.00) 51609.80 (3108.63) 74.75 (9.38) 457.62 (27.64) 0.17 (0.00)CTCP 99.24 (0.00) 32270.00 (1807.87) 208.10 (27.16) 284.68 (16.08) 0.15 (0.01)Table 9. Compound TCP versus DCCP CCID3 with Application CBRDelivery Rate (%) Sent Packets(packets)Dropped Packets(packets)AverageThroughput (Kbps)Average End toEnd Delay (s)CTCP 99.41 (0.00) 54090.80 (2770.72) 241.70 (13.80) 478.25 (24.58) 0.15 (0.01)DCCP CCID3 99.60 (0.00) 40856.20 (4057.67) 113.00 (9.95) 361.73 (36.06) 0.15 (0.00)DCCP’ variants have also been compared with CUBIC and the results point to a better performance ofCUBIC, due to its more aggressive congestion control. Specifically, CUBIC has shown much faster reactionto dropped packet events, what is evidenced in Figure 4 and Figure 5. Queue Size chart presents a high linkoccupation, with the queue size achieving 300 packets many times. Window Size chart presents a high216