Network Design

Hi,

I need some advise really. I have been asked to look into ideal solution to a networking issue. I was hoping you might have some insight..

Currently there are 3 sites. Approx 300 staff at one and 150 at each of the other two. Each building is within 15 miles.

There is no traffic model however we host our own e-commerce site and would like to keep all secure information onsite.

Security and reliability are key points.