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Kerberos Authentication: In Greek mythology, Kerberos is the monstrous three-headed dog that guards the entrance to Hades. Indeed, we can view modern-day Kerberos Authentication as the god who guards the entrance to a network’s resources.
Kerberos Authentication, a computer network authorization protocol, was originally invented and published by MIT. This system allows individuals communicating over a [...]

Before you understand the many Firewall Protections, you should know firewall’s limitations first.
Here they are:

not guarantee data integrity
not support authenticity of the source of data
no control over how the packets were created
not support confidentiality- no encryption among different firewalls unless it is incorporated with VPN features
don’t protect against some Internet threats like virus attack and/or password [...]