For decades, the corporate LAN was a self-contained entity. What happened on LAN stayed on the LAN. This had its disadvantages – mobility wasn’t easy, for instance – but in many ways made for a network that hummed along nicely. Security, for instance, was nice and simple: Everything (theoretically) was safe and sound behind the firewall, provided appropriate security was in place. Though it didn’t always work out that way, the essential mindset was that IT could account for, track and secure everything.