H ELECTRICITY
H04 ELECTRIC COMMUNICATION TECHNIQUE
H04L TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
H04L63/00 Network architectures or network communication protocols for network security
H04L63/02 for separating internal from external traffic, e.g. firewalls
H04L63/0209 Architectural arrangements, e.g. perimeter networks or demilitarized zones
H04L63/0218 Distributed architectures, e.g. distributed firewalls