What is the difference between conectionless and connection-oriented protocol?

Answer 1

A connectionless protocol is one where the client does not make a connection to the server. This is typically the UDP subprotocol of TCP/IP. There is one packet sent for each message. The client and server applications are responsible for all validation, sequencing, and acknowledgment issues. Its a little like standing in a field with a megaphone. You yell out your message and, if someone hears it that needs to hear it, they answer with their own megaphone. If you don't get an answer, you wait a bit and try again. A connection-oriented protocol is one where the client establishes a connection for each conversation with the server. This is typically the TCP subprotocol of TCP/IP. There can be many packets sent back and forth during the conversation, but that is no longer the concern of the application. The protocol stacks on each machine are responsible for validation, sequenceing, acknowledgement, retries, etc. Its a little like making a telephone call. You pick up the phone and dial a number. The other party may or may not answer, but when they do you can have a conversation.