Routing is an extremely important function of IP. It is the process of choosing a path over which to send packets. The device that performs this task is called a router, which forwards packets from one physical network to another. Your knowledge of IP will enable you to see the correlation between IP and routing.
The Internet layer, or OSI/RM network layer (Layer 3), performs the routing function. A packet, or datagram, carries sufficient information for routing from the originating host to the destination host using the IP address. Packets may traverse several networks before reaching their destination host.
Packets are routed transparently, and not necessarily reliably, to the destination host. The term "transparent," when applied to routing, means that after the routing hardware and software are installed, changes are undetectable by users because the routing process is largely automated. The complexity of routing is not visible to the user. The transport or application layer is responsible for reliability, which ensures that the data arrives at the other end.
Routing can be summarized as:
- The process that determines the path that packets will travel across networks.
- One of the most important IP functions.