Empirical TCP profiles and application

We characterize a TCP implementation by a function, called a profile, that expresses the instantaneous throughput at the source in terms of the instantaneous roundtrip time and instantaneous loss rate for bulk transfers. We empirically obtain profiles of several TCP implementations, accurately enough to distinguish not only the TCP version but also the implementation (BSD, Windows, etc). Profiles have several uses: comparing different TCP implementations, diagnosing a TCP implementation, quantifying TCP-friendly flows, etc. We devise a method that uses profiles to compute the time-evolution of instantaneous performance metrics (throughput, queue size, loss rate, etc.) of TCP networks. Comparison against ns simulations shows the method to be accurate and fast.