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An Investigation into Transport Protocols and Data Transport ...

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8.3. Results 177<br />

10<br />

100<br />

Total Throughput (mbit/sec)<br />

9<br />

8<br />

7<br />

6<br />

St<strong>and</strong>ardTCP<br />

BicTCP<br />

FAST<br />

5<br />

HSTCP<br />

HTCP<br />

ScalableTCP<br />

St<strong>and</strong>ardTCP ns2<br />

4<br />

10 100<br />

RTT (msec)<br />

(a) 10Mbit/sec Bottleneck Capacity<br />

Total Throughput (mbit/sec)<br />

95<br />

90<br />

85<br />

80<br />

75<br />

St<strong>and</strong>ardTCP<br />

70<br />

BicTCP<br />

FAST<br />

HSTCP<br />

65<br />

HTCP<br />

ScalableTCP<br />

St<strong>and</strong>ardTCP ns2<br />

60<br />

10 100<br />

RTT (msec)<br />

(b) 100Mbit/sec Bottleneck Capacity<br />

240<br />

Total Throughput (mbit/sec)<br />

220<br />

200<br />

180<br />

160<br />

St<strong>and</strong>ardTCP<br />

BicTCP<br />

FAST<br />

HSTCP<br />

HTCP<br />

ScalableTCP<br />

St<strong>and</strong>ardTCP ns2<br />

10 100<br />

RTT (msec)<br />

(c) 250Mbit/sec Bottleneck Capacity<br />

Figure 8.31: Aggregate Goodput of a St<strong>and</strong>ard TCP flow competing against a<br />

New-TCP flow with symmetric network conditions (Bottleneck Queuesize set to<br />

20% BDP).<br />

The interaction between St<strong>and</strong>ard TCP <strong>and</strong> FAST is shown in Figure 8.34<br />

<strong>and</strong> shows that the increase in average queue occupancy of the St<strong>and</strong>ard TCP<br />

flow causes the FAST flow to back away due to the delay-based response<br />

to congestion control of FAST. The effect of this approach is that FAST<br />

exhibits an almost opposite representation of the St<strong>and</strong>ard TCP goodput.<br />

The result of this is that FAST is especially friendly under environments<br />

where St<strong>and</strong>ard TCP is incapable of high goodput, but also implies that the<br />

FAST flow actually achieves less goodput at the cost of increased fairness<br />

with St<strong>and</strong>ard TCP.

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