An Investigation into Transport Protocols and Data Transport ...

9.1. Transfer Tests Across Dedicated Private Wide Area Networks 193
the goodput and fairness characteristics of the aggregate traffic.
Impact
The primary aim of New-TCP proposals is to utilise the available link bandwidth
better. However, the result of this increased utilisation is that it
will disrupt the traditional ‘background’ traffic sharing the link by ‘stealing’
bandwidth from Standard TCP flows and causing unfriendliness (See Section
8.3.3). The amount by which New-TCP algorithms affect varying numbers
of legacy Standard TCP bulk transport flows can be defined through a
impact which provides an interpretation of fairness and an indication of how
intrusive a New-TCP algorithm is:
Impact =
B(n) − B(i)
B ′ (n) − B ′ (i)
(9.1)
Given a pipe with n TCP flows, define B(n) to be the aggregate goodput
of n Standard TCP flows and B(i) to be the goodput of i Standard TCP
flow in the presence of the aggregate. Under identical network conditions,
also define B ′ (n) to be the aggregate goodput of n flows, of which n − i
flows are that of Standard TCP flows in the presence of i New-TCP flows.
Furthermore, define that B ′ (i) is the aggregate goodput of i New-TCP flows.
As such, the impact provides the ratio of achieved goodput of the Standard
TCP aggregate with and without the inclusion of i flows of New-TCP.
Therefore, this represents the impact of i New-TCP flows upon the goodput
achieved by n Standard TCP bulk transport users compared to that of Standard
TCP flow. A value of UIF > 1 means that the goodput experienced
by a legacy TCP flow as a result of being run concurrently with a New-TCP
flow is diminished due to the aggressiveness of the New-TCP algorithm.