An Investigation into Transport Protocols and Data Transport ...

9.1. Transfer Tests Across Dedicated Private Wide Area Networks 194
1000
1000
Goodput (mbit/sec)
100
10
HSTCP
HSTCP Theory
HTCP
ScalableTCP
ScalableTCP Theory
Standard TCP
Standard TCP Theory
1
1e-06 1e-05 0.0001 0.001 0.01 0.1 1
Induced Loss Rate (packets)
Goodput (mbit/sec)
100
10
HSTCP
HSTCP Theory
HTCP
ScalableTCP
ScalableTCP Theory
Standard TCP
Standard TCP Theory
1
1e-08 1e-07 1e-06 1e-05 0.0001 0.001 0.01
Induced Loss Rate (packets)
(a) MBNG
(b) DataTAG
Figure 9.1: Response Function of New-TCP over dedicated test networks.
9.1.2 Calibration
A calibration test was conducted to ensure the appropriate implementation of
the New-TCP algorithms under the altAIMD 0.3 kernel. This was achieved
by comparing experimental results with that of theory for the response function
(See Section 5.4.2).
This was performed between a single pair of end systems where packets
were selectively dropped at the receiver in a regular fashion making use of a
kernel modification to achieve the drop. The implementation of this packet
drop relies on the counting of all received data packets at the receiver whereby
the checksum for every n’th packet is declared invalid in order to simulate
bit error on the network path and at packet loss rate of p = 1/n.
Figure 9.1 shows that the introduction of a single packet drop per window
is handled well in the kernel, and that the experimental results match very
closely to theory for both networks. And in agreement with theory, ScalableTCP
is consistently able to obtain better or equivalent throughput than
both HSTCP and H-TCP over the range of the drop rates.
It can be seen that the mode switch from low to high speeds matches
closely to theory and is handled well in ScalableTCP and HSTCP in the low