An Investigation into Transport Protocols and Data Transport ...

9.2. Preferential Flow Handling Using DiffServ 214
It can be argued that ScalableTCP, especially under long latency environments
experiences unfairness between competing flows. This was often
observed with either a large distribution of per flow goodputs and or frequent
outlying points which show that a small number of flows often achieved much
higher goodput than that of the other flows.
9.2 Preferential Flow Handling Using Diff-
Serv
The recent decrease in price to link capacity ratio has meant that it is much
more cost effective to upgrade the capacity of the network rather than to
engineer a lower speed one. This acceleration is much faster than the observed
bandwidth usage from traditional Best Effort (BE) traffic. Thus in the short
to medium-term there is excess capacity available, especially in the core.
However, as shown in Section 9.1, Standard TCP is incapable of utilising
such spare capacity due to slow growth of its congestion windows and the
requirement for very low loss rates.
Another problem is that due to the implementation issues of the Linux
kernel and the processing overheads of SACKs, transport of New-TCP algorithms
in Best Effort (BE) environments at high speeds is difficult.
One way in which it is possible to utilise this spare capacity is to implement
some form of mechanism in the network whereby network users can be
differentiated to offer better (or worse) service, depending on a number of
factors; such as their price plan, types of traffic or network usage.
The different service qualities can be addressed by a variety of mechanisms.
However, the actual deployment of those mechanisms in the current