RFG believes firewalls are crucial elements for the overall security architecture in the enterprise. IT executives should establish business application profiles (BAPs) describing the security requirements for each of their company’s applications. Firewalls should be deployed to create “zones” of authorized types of traffic, separating applications into groups of related security requirements. One firewall is rarely sufficient protection; one firewall is often used to protect internal systems, such as those in the data center, from internal misuse, in addition to protecting public servers from the dangers of being accessible from the Internet.”]
Source: https://www.csoonline.com/article/2113273/best-practices-for-firewall-deployments.html