Network Layout
Obviously having the best rules and fastest firewall, do nothing if it is placed poorly on a network. Systems need to be protected against outside threats, inside threads, other systems, etc.. And this can only happen with proper placement of a firewall or firewalls.
Firewalls also need to be considered mission critical systems in companies dependant upon networks to accomplish their task. Therefore, redundant and scalable systems need to be put in place or available to handle emergencies.