Network layer firewall: Difference between revisions

Revision as of 11:57, 17 December 2006

Revision as of 22:32, 1 March 2007

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In [[computer networks]], a '''[[network layer]] [[Firewall (networking)|firewall]]''' works as a [[packet filter]] by deciding what [[packet]]s will pass the firewall according to rules defined by the administrator. Filtering rules can act on the basis of source and destination address and on [[Computer port (software)|port]]s, in addition to whatever higher-level [[network protocol]]s the packet contains. Network layer firewalls tend to operate very fast, and transparently to users.

Network layer firewalls generally fall into two sub-categories, [[stateful firewall|stateful]] and [[stateless firewall|stateless]]. [[State|Stateful]] firewalls hold some information on the state of connections (for example: established or not, initiation, [[handshaking]], [[data]] or breaking down the [[Connectivity (computer science)|connection]]) as part of their rules (e.g. only hosts inside the firewall can establish connections on a certain port).

Stateless firewalls have packet-filtering capabilities but cannot make more complex decisions on what stage communications between hosts have reached. Stateless firewalls therefore offer less security. Stateless firewalls somewhat resemble a [[router]] in their ability to filter packets.