An Investigation into Transport Protocols and Data Transport ...

9.1. Transfer Tests Across Dedicated Private Wide Area Networks 202
Normalised Goodput (mbit/sec)
4
3.5
3
2.5
2
1.5
1
0.5
Mean Goodput
400
350
300
250
200
150
100
50
Mean TCP Flow Goodput (mbit/sec)
Normalised Goodput (mbit/sec)
4
3.5
3
2.5
2
1.5
1
0.5
Mean Goodput
400
350
300
250
200
150
100
50
Mean TCP Flow Goodput (mbit/sec)
0
2 3 5 9 17 25 33 49
Number of Flows
0
0
2 3 5 9 17 25 33 49
Number of Flows
0
(a) HSTCP
(b) ScalableTCP
Normalised Goodput (mbit/sec)
4
3.5
3
2.5
2
1.5
1
0.5
Mean Goodput
400
350
300
250
200
150
100
50
Mean TCP Flow Goodput (mbit/sec)
Normalised Goodput (mbit/sec)
4
3.5
3
2.5
2
1.5
1
0.5
Mean Goodput
400
350
300
250
200
150
100
50
Mean TCP Flow Goodput (mbit/sec)
0
2 3 5 9 17 25 33 49
Number of Flows
0
0
2 3 5 9 17 25 33 49
Number of Flows
0
(c) H-TCP
(d) Standard TCP
Figure 9.9: Fairness between various number of concurrent parallel New-TCP flows
on DataTAG.
80%. ScalableTCP achieves similar goodputs to that of the other New-TCP
algorithms with a small number of flows, but is able to achieve utilisation
with more flows.
Figures 9.8 and 9.9 show the fairness distributions of running numerous
concurrently parallel flows of each algorithm. Under the low latency network
of MB-NG, it was observed that ScalableTCP appears to have poor fairness
for 5 or more flows, with 33 flows demonstrating severe unfairness. However,
this is also true of the other algorithms - including Standard TCP. It can
be argued that the fairness performances of HSTCP, H-TCP and Standard
TCP are comparable under this low latency environment.
With the longer latencies of DataTAG, the lower mean goodput of each
Standard TCP flow is apparent. Out of all of the algorithms, H-TCP appears
to have the best fairness, with the smallest distribution of goodputs for all