libutp

> that actually works as well as they do. I doubt most CS grads could do this. One hard part of it is the p2p (but that's already been solved [0]). Having a project that large where you don't eventually shoot yourself in the foot because of architecture and finish in a reasonable time without using too many resources on a user's computer is also a hard part. [0] https://github.com/bittorrent/libutp

It's pretty much impossible to saturate even a LAN connection with a single TCP connection. The are a number of issues at play here — RTT (Round Trip Time, i.e. ping/latency), window sizes, packet loss and initcwnd (TCP's initial window). The combination of the limitations imposed by the speed of light and TCP's windowing system means that you are buggered transferring large files over high-latency TCP connections. I haven't checked their figures, but here's a TCP rate calculator I just found which lets you tune the different parameters: http://osn.fx.net.nz/LFN/ The greater the delay, the bigger the impact. For example if we take a standard Windows XP machine and plug in the values for a standard Gigabit LAN (typically .2ms latency between hosts) we get a maximum speed of 700Mbit/sec, but if we try if between two hosts, one of them in th