Subject: Advanced Networking Technologies

Difficulty: Medium

Marks: 5 marks

Packet Filtering:

It is considered to be most basic type of firewall. It receives the packets and the revaluates them based on set of rules that are usually in the form of access control. These packets maybe forwarded to their destination, dropped or dropped with the return message to the sender describing the situation. The type of filtering rules varies based on the application. Mostly following rules are used:

• Source and Destination IP address: Packets from certain IP addresses are only allowed to pass blocking other addresses. This will make firewall drop packets which do not belong to defined source address.
• Source and destination ports: Packets from defined ports are accepted and those packets which are not defined.
• Direction of traffic: Allows traffic only in defined direction. That is allows only either inbound packets or outbound packets.
• Type of protocol: Passes or drops packet of certain protocols only such as IP, TCP, and User Datagram Protocol etc.
• The packet’s state: It passes packets based on the state of packets such as ACK or SYN where SYN meaning synchronizing packet or ACK meaning Acknowledgement packet.