The IP forwarding algorithm

IP forwarding algorithm

The IP forwarding algorithm is related to the topic of routing and gives a more directed approach in forwarding datagrams over a network. In order to achieve a successful transfer of data the algorithm uses a routing table to select a next-hop router as the next destination for a datagram...

 is related to the topic of routing

Routing

Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...

 and gives a more directed approach in forwarding datagram

Datagram

A datagram is a basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order are not guaranteed....

s over a network. In order to achieve a successful transfer of data the algorithm uses a routing table to select a next-hop router as the next destination for a datagram. The IP address

IP address

An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...

that is selected is known as the next-hop address.

The IP Forwarding Algorithm states:

Given a destination IP address, D, and network prefix, N:

if (N matches a directly connected network address)



    Deliver datagram to D over that network;



else if (N does not match a network address

         and routing table contains route for N)



    Send datagram to next-hop address listed in the routing table;



else if (N does not match a network

         and routing table does not contain route for N

         and there exists a default route)



    Send datagram to default route;



else



    Send forwarding error message;