Cygwin translates calls to Windows via cygwin.dll. It works well for the most part, but in some corner cases, it doesn't work so well.
> Microsoft research technology to basically perform real time translation of Linux syscalls into Windows OS syscalls
Running the Linux kernel on Windows has been done before IIRC - coLinux?
This version is taking the native Ubuntu binaries and executing them directly against the Windows API via a real time translation later.
The difference is like playing a game using virtualization technology vs. WINE. As the complexity of the game increases, the former begins to slow down and break.
You don't have to be a fan of Microsoft but they deserve at least some credit.
Edit: thinking about it I'm not sure if I'm right. Or does Cygwin map the ping command to the Windows command?
It looks like Cygwin has a ping package, but it isn't something you'll get unless you specifically select it in the installer.