Rate Control State-of-the-art Survey

The majority of Internet traffic use Transmission Control Protocol (TCP) as the transport level
protocol. It provides a reliable ordered byte stream for the applications. However, applications such
as live video streaming place an emphasis on timeliness over reliability. Also a smooth sending rate
can be desirable over sharp changes in the sending rate. For these applications TCP is not necessarily
suitable. Rate control attempts to address the demands of these applications. An important design
feature in all rate control mechanisms is TCP friendliness. We should not negatively impact TCP
performance since it is still the dominant protocol.
Rate Control mechanisms are classified into two different mechanisms: window-based mechanisms
and rate-based mechanisms. Window-based mechanisms increase their sending rate after a successful
transfer of a window of packets similar to TCP. They typically decrease their sending rate sharply
after a packet loss. Rate-based solutions control their sending rate in some other way. A large subset
of rate-based solutions are called equation-based solutions. Equation-based solutions have a control
equation which provides an allowed sending rate. Typically these rate-based solutions react slower to
both packet losses and increases in available bandwidth making their sending rate smoother than that
of window-based solutions. This report contains a survey of rate control mechanisms and a discussion
of their relative strengths and weaknesses. A section is dedicated to a discussion on the enhancements
in wireless environments.
Another topic in the report is bandwidth estimation. Bandwidth estimation is divided into capacity
estimation and available bandwidth estimation. We describe techniques that enable the calculation of
a fair sending rate that can be used to create novel rate control mechanisms.