Connectionless routing is a method of transmitting data in computer networks, in which each packet is treated separately, making its way through the network independently.
Each individual packet may take a different route through the network depending on the type of routing protocol used and the amount of traffic on the network. Since the packets travel along varying routes, they may not necessarily arrive at the designated location in sequence. To ensure proper sequencing, the sending computer assigns a sequence number to each of the packets along with information regarding the message stream to which the packet belongs. The network layer on the receiving computer then reassembles the packets in the correct sequence prior to passing the packets to the application layer.