Why do you type sudo before the command? There is absolutely no reason to have root privileges to run this command.
I just tried again as a regular user and it works. Try this:
git clone git://git.kernel.org/pub/scm/linux/kernel/git/pjt/linsched.git
Or better, pick only what you need as this repository is very big.
Anyhow, the connection problem may be transient, be it on your side or on the server's side.
Is there any other simulator?
Probably, but it's hard to answer not knowing what you want achieve.