Connectionless describes communication between two network end points in which a packet can be sent from one side to another. Connectionless means that there is no dedicated end-to-end connection before data is sent. IP connectionless is theoretically comparable to sending a letter to someone without notifying the recipient in advance. all the same; the device at one side transmits the packet to the other, without ensuring that the recipient is available and ready to receive the data. If there are problems with the transmission, it may be necessary to resend the data several times.
Connectionless data communications work on the principle where the initial exchange of control information is not required to establish an end-to-end connection before packets are forwarded. IP also does not require additional fields in the header to maintain an established connection. This process reduces the overhead of IP. But, with no pre-established end-to-end connection; senders are unaware whether destination devices are present and functional when sending packets; nor are they aware if the destination receives the packet, or if they are able to access and read the packet.
The Internet Protocol (IP) and User Datagram Protocol are connectionless protocols. These protocols are generally described as stateless because the endpoints have no protocol-defined way to remember where they are in a “conversation” of message exchanges. The alternative to the connectionless is connection-oriented protocols, which are described as stateful because they can keep track of a conversation.