When a message is sent from one computer to another, the TCP protocol first divides the message into small manageable units called packets. Each packet contains the data itself, the address of the sender and the receiver along with the sequencing information necessary to make sure that the data resembles correctly when it arrives at the destination. The IP protocol then comes into the picture. It appends the IP address of the source and destination of the computer to each packet. It then transports data stored in packets along different routes through a series of routers. Every router examines the destination address of the packets it receives and sends it across the network using the fastest path available. If the most direct path to the destination is not working then it sends the packets along an alternative path. Because of the change of routes, some packets arrive out of order. Here, the TCP protocol takes over the control again. It puts the packets back in the order and then reassembles them into the original message.