Packet Filtering

This article explains packets, packet headers, and packet filtering. What can the option of allowing or disallowing packets be based on? What are the weaknesses and advantages of packet filtering? After you read, you should be able to describe packets and packet headers.

3. Circuit relay

A circuit level gateway is a firewall that validates connections before allowing data to be exchanged. This means that it does not simply allow or deny packets based on the packet header but determines whether the connection between both ends is valid according to configurable rules before it opens a session and allows data to be exchanged. Filtering is based on:

Source/destination IP address
Source/destination port
A period of time
Protocol
User
Password

All traffic is validated and monitored, and unwanted traffic can be dropped.

Weakness:

Operates at the Transport Layer and may require substantial modification of the programs that normally provide transport functions