An Investigation into Transport Protocols and Data Transport ...

6.2. Discussion and Deployment Considerations of New-TCP Algorithms125
work transport performance and efficiency in order to maximise the network
resource utilisation. As the Standard TCP AIMD algorithms have been
proven to be very robust, replacement algorithms for TCP should also be as
robust. Furthermore, the development of new transport protocols must be
scalable with network capacities and adaptable to different types of transmission
medium and different types of applications.
Congestion control can be interpreted as a distributed optimisation problem
where sources and links carry out a distributed computation to maximise
the sum of individual source utilisations [LPD02, LS03].
As high speeds networks become more prevalent on today’s Internet, it
is important to be able to utilise the spare capacity quickly. This inherently
implies that the deployment of New-TCP algorithms should be compatible
with the standard windowing mechanisms of TCP [Pos81b]. All of the algorithms
in this survey are sender side modifications to the congestion control
algorithm and therefore only requires the modification of the sending host
to facilitate high throughput transfer - with sufficient network resources and
tweaking as outlined in Chapter 5.
6.2.1 Scalability and Network Utilisation
One problem of Standard TCP being able to attain high speeds is that a
very low loss rate is required in order to maintain large values of cwnd. As
Standard TCP cannot differentiate between packets lost to congestion and
that lost to transmission errors this becomes a serious problem on lightly
loaded networks.
However, the primary reason for requiring a replacement congestion control
algorithm is that Standard TCP, with its linear cwnd increase, simply