D-Link DFL-2500 User Guide - Page 88

10 CHAPTER Routing 10.1 Overview Routing is a major role in the network layer (OSI layer 3), which determines how to transport packets from the initiating host to the desired receiving end. The devices functioning at the network layer, such as routers or firewalls, perform routing to achieve two tasks primarily, the Path Determination and the Packet Switching. Path determination Before any packet can be sent from the sender to the receiver, a path need to be determined for the packet to travel through. Located in the heart of any routing capable device, like a firewall or a router, is the routing table, a map that provides all the path selections. Each entry in this mapping table describes an available route. The definition of the route here is the connection that links the two communication ends and also all the intermediate routing devices. The description of route inside the routing table indicates the address of the receiver, and where is the next stop(hop) the packet should go to get one step closer to its destination, since in the network circumstance, it is common to have more than one device sitting along the way. These contents are stored in the table as different 69