An Investigation into Transport Protocols and Data Transport ...

9.1. Transfer Tests Across Dedicated Private Wide Area Networks 198
9.1.4 Results: CBR Background Traffic with 10 New-
TCP Flows
Figure 9.4 shows the goodput of running 10 New-TCP flows against varying
amounts of CBR traffic and shows that on both networks, the aggregate
goodput of all algorithms were almost identical - including that of Standard
TCP on the DataTAG network. Generally, ScalableTCP and H-TCP are
able to squeeze a little more out of the available bandwidth than the other
algorithms on MB-NG, yet achieved similar rates to HSTCP on DataTAG.
ScalableTCP was also able to achieve a little more combined goodput at
around 500Mbit/sec CBR background on the long latency link of DataTAG.
Figures 9.5 and 9.6 gives a representation of the fairness between the 10
New-TCP flows on the MB-NG and DataTAG respectively. They show boxplots
representing the range and quartiles of the achieved mean goodput of
the 10 competing New-TCP flows under each CBR background rate. In order
to give a comparative analysis of the fairness in each network environment,
the box-plots are normalised by the mean goodput of the flows which is plotted
on the secondary y-axis. While the aggregate goodput results gathered
represent the means and standard deviations on the mean of many iterations
of the tests, the figures shown only present that of a single iteration.
Under MB-NG the fairness distribution between H-TCP flows was similar
to that of Standard TCP. It can be argued that ScalableTCP shows a
greater variation in the fairness distribution between flows with less competing
background traffic. However, ScalableTCP shows similar fairness to that
of the other algorithms at higher background rates (i.e. lower average TCP
goodputs).
However, it was observed that there was a wider distribution of goodput