Tweaking TCP

I just had fiber optics installed today, 15M/2M is the speed. When I do a speed test, the download speed comes in around 6-7MB. The Verizon tech had me download the Dr. TCP tool from a web site (link below) that I can run on Windows and insert settings he gave me to get over 13-14MB download speeds. Now I am trying to figure out how I can do the same for my SuSE Linux box. Anyone know what I can do? The settings he has me set are described in Dr. TCP as 'Tcp Receive Window' and 'MTU'. Here is the site where I got Dr. TCP: http://www.dslreports.com/drtcp -- Robert