Explain about the network level in detail.
Network Level Firewall/Packet Filters:
At the Network level firewalls operate upon the mechanism of filtering individual IP packets by using the routers.
Packet filters, termed “access control lists” onto Internet routers give the rudimentary through security.
Filters are configured to permit/discard packets based upon attributes as like:
1. Exact source or destination IP addresses
2. Exact protocol forms
3. Exact source or destination port numbers
4. TCP flags set/clear into the packet header