Firewalls are network devices that are used to enforce security policies within a network; they can also be used to control the traffic between networks. The technology that was used to execute the firewall problem is Firewall Services Modules (FWSM). There are different types of firewalls that are in existence. They include packet-filtering firewalls, application and packet inspection firewalls. Each is discussed in the sections that follow.
The first type of firewall is packet-filtering firewalls which use protocols, the destination and source of the packet, the port numbers of the source and destination, the time range, and the Differentiate Service Code Point (DSCP) and the many parameters of the header section. They are known to use Access Control Lists (ACL) on routers and switches; they are also known to be very fast. The working of the firewall is that as the traffic enters and exits the interface, the ACL will match the criteria that has been chosen and will either deny or allows the packets to proceed. They are used in situations where the circuit that is used is Application Specific Integrated Circuit (ASIC).
This type of firewall works at layer seven of the OSI Model. The working of this is that the device work on behalf of the client. The firewall will send the request form the user and will then authenticate the request before they are approved and made available to the user (Vacca,, Ellis, 2005).
Packet inspection firewall
These firewalls operate by looking at the session information that re found in between devices. The information that are important to the firewall include the protocol, the connections which are new or those which are existent, the checksum of the IP and the information which are specific to the application.
The best firewall is the application firewall. The reason is that the applications will go through one authentication and they have to be approved by admin.
Vacca, J., Ellis, S. & Ellis, Scott, H. (2005). The talomh tool lonh. New York: Elseview