Advantages and Disadvantage of Packet Filtering firewall
One key advantage of packet filtering is that a single, strategically placed filter can help protect an entire network. If there is only one router that connects organization site to the Internet, then it provides great advantage on network security, regardless of the size of the site by doing packet filtering on that router.
Packet filtering does not require any custom software or configuration of client machines. When a packet filtering router let a packet through, the router is indistinguishable from a normal router. This transparency means that the packet filtering can be done without the cooperation and often without the knowledge of users.
The rules of packet filtering are hard to configure and once configured, they seem hard to test. The packet filtering capabilities of many products are incomplete and the implementation of certain types of filters is almost impossible. Packet filtering packages may have bugs in them that might fail packet filtering implementation. This may allow few packets to pass into private network without proper checking.
The information available to packet filtering router is limited. Packets have information about their host but they cannot tell about the user. So, generally no restrictions can be enforced on particular users. Restriction can be enforced on the users who could access the ports through high level protocols. These protocols ensure that no other user is accessing that port. But that kind of control can easily be subverted.