In connectionless routing, each packet is treated separately, making its way through the network independently.

Each individual packet may take different routes through the network depending on the type of routing protocol used and the amount of traffic on the network. As the packets travel along varying routes, they may not necessarily arrive at the designated location in sequence.

To overcome this problem, the sending computer will assign a sequence number to each of the packet along with information regarding the message stream to which the packet belongs. The network layer on the receiving computer would then reassemble the packets in the correct sequence prior to passing the packets to the application layer.