Did you ever get that feeling when you walk into a room and you can literally feel the tension between people? I do quite often as I visit customers and enter a room with security and network engineers. Sometimes they are literally sitting on opposites sides of the room from each other.
Mind the Gap
From a traditional standpoint, security is handled by the security engineers and networking is handled by the network engineers. Most of the time each group has their own take on security. The security engineers will state that security is enforced in the firewall (their domain).