An Investigation into Transport Protocols and Data Transport ...

7.2. Environment 142
control algorithms over a wide range of environments, the metrics defined in
Section 7.1 are applied to a series of different experiments designed to show
the differences between the New-TCP algorithms.
The following network conditions can effect the performance of TCP
transport. It is therefore desirable to test over a range of different network
environments encompassing these conditions to obtain a good representation
of New-TCP performance.
Network Capacity & Link Latency Greater link capacities result in larger
values of cwnd and hence the number of packets in flight. Similarly,
longer latencies also result in larger values of cwnd. It is also important
to understand the affects of how these algorithms will ‘switch’ into their
high speeds modes and how that may adversely affect the performance
metrics outlined in Section 7.1.
Bottleneck Queue Size As mentioned in Section 5.4.1, the buffering of
packets is important to absorb packet bursts and to increase bulk transport
efficiency. The dynamic of the queue provision is also important
as competing web traffic may affect the metric dynamics of the New-
TCP flows. Whilst the short term dynamics of web traffic is not well
understood [BPS + 98, CB95], it is argued that the bulk transfer of data
will play an important part in future networks.
Number of Flows (and type) It is important to gauge the scalability of
these flows in terms of how they share bandwidth. In terms of friendliness,
it is also important to measure the unfairness of New-TCP flows
against Standard TCP. Related to the bottleneck queue dynamics, the
burstiness of TCP flows may also affect the various performance metrics
such as convergence time and overhead.