I will check the router settings for GRE47 and read more about it. I was reading
on a website that for a D-Link router we do not need to do any settings for
that. The only thing needed is to port forward to 1723. I will double check it
and get back.

I read alot of people using OpenVPN. But, from what I read, there is not
much learning curve associated with it. And, I thought that if once I learn the
nuts and bolts I will move on to more protocol e.g. L2TP, IPSec etc.