Which of the following statements correctly describe network packet filtering at the IP layer? (Select all that apply)

A. Most IP Packet filtering firewalls determine what packets to filter based upon a set of rules which can be configured for a particular network or host. B. IP packet filtering determines which IP packets may flow into or out of a network or a computer. C. Most IP packet filtering firewalls determine what to filter based upon the IP header fields. D. IP packet filtering may either be applied to the perimeter of a network, or to individual hosts within a network, but it cannot be applied to both at the same time.