that it was one of the earliest routing protocols to be developed. One other problem posed by the use of RIP is that sometimes a destination may be located too far away to be reachable. When using RIP, the maximum number of hops that data can be forwarded through is fifteen. The destination network is considered unreachable if it is more than fifteen router hops away. At the data link layer, an IP datagram is encapsulated into a frame. The datagram, including the IP header, is treated as data. A router receives the frame, strips off the frame header, then checks the destination IP address in the IP header. The router then looks for that destination IP address in its routing table, encapsulates the data in a data link layer frame, and sends it out to the appropriate interface. If it does not find the destination IP address, it may drop the packet. Routers are capable of supporting multiple independent routing protocols, and of maintaining routing tables for several routed protocols, concurrently. This capability allows a router to deliver packets from several routed protocols over the same data links. Most network services use a connectionless delivery system. They treat each packet separately, and send it on its way through the network. The packets may take different paths to get through the network, but are reassembled when they arrive at the destination. In a connectionless system the destination is not contacted before a packet is sent. A good analogy for a connectionless system is a postal system. The recipient is not contacted before a letter is sent from one destination to another. The letter is sent on its way, and the recipient learns of the letter when it arrives. In connection-oriented systems, a connection is established between the sender and the recipient before any data is transferred. An example of a connection-oriented network is the telephone system. You place a call, a connection is established, and then communicat...
