An Investigation into Transport Protocols and Data Transport ...

8.4. Discussion of Results 183
Asymmetric
New-TCP Symmetric Small Buffer Large Buffer Friendliness
Standard TCP 0.87±0.05 0.34±0.04 0.40±0.04 0.87±0.05
BicTCP 0.97±0.02 0.01±0.00 0.02±0.00 0.07±0.00
FAST 0.31±0.14 0.10±0.00 0.11±0.00 0.44±0.00
HSTCP 1.00±0.00 0.05±0.00 0.05±0.00 0.05±0.00
H-TCP 1.00±0.00 0.59±0.00 0.59±0.13 0.06±0.00
ScalableTCP - 0.01±0.00 0.01±0.00 0.01±0.00
Table 8.2: Summary fairness of two competing New-TCP flows at 250Mbit/sec
bottleneck and 82ms RTT.
in FAST’s throughput which can be less than that of Standard TCP.
As expected, HSTCP shows very little deviation from Standard TCP
goodput at low speeds, but the increase of BDP shows HSTCP to be as
aggressive as the other algorithms as larger cwnd values are reached.
H-TCP has similar goodput performance to that of HSTCP.
8.4.2 Fairness and Friendliness
Whilst the fairness between symmetric flows was not expected to be a difficult
test for the New-TCP algorithms, results showed otherwise. This was most
noticeable for ScalableTCP and FAST and is demonstrated in Table 8.2. In
the former case, unfairness resulted primarily because of the long convergence
times required due to the small back-offs experienced by the high throughput
flow which requires many congestion epochs to result in fair share between
flows.
FAST, on the other hand, appears to have instability issues across the
tested environments which result in both short term and long term unfairness
issues. Unlike the loss-based algorithms, the dynamics of FAST are
very dependent upon the queue size allocation. At small sizes, the aggres-