Modeling TCP Performance
Allen B. Downey
Research Fellow, Boston University


During long downloads, many Web browsers display estimates of the
remaining transfer time.  Unfortunately, these estimates are so
inaccurate that most users have learned to ignore them.  To address
this problem, I am trying to identify the properties of a network path
(and the endpoints) we have to know in order to predict the duration
of TCP transfers.

Based on measurements from a diverse set of network paths, I have
developed a model of TCP performance that captures a wide range of the
behavior seen in the Internet, including oddities like
nondeterministic slow start.  Although the resulting model is
complicated, I will show that we can estimate its parameters with
simple, application-level measurements.