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Connection-oriented vs. connectionless Protocols

Connection oriented

Connection oriented requires a session connection be established before any data can be sent. Therefore, connection oriented often called a reliable network service. Example for connection oriented is TCP, has many advantages when it transit data over network.
In TCP have three operations:
  1. Authentication: When sender contacts with receiver, they agree establish a connection, authentication occurs.
  2. Data transmission: During this part of the process, the sending computer waits for acknowledgement message between each part of the transmission. If an acknowledgement is not received, that portion of the transmission is resent until it has been received without error. Therefore, we have when packet is sent to destination. A transmission sent over the network using a connection oriented is received in the same order in which it was sent, and does not require routing information.
    These features improve the speed and accuracy of data transmission.
  3. Break the connection: when the data transmission is completed, the connection is broken. If further data needs to be sent between the two devices, a new connection must be initiated.


Connectionless does not require a session connection between sender and receiver. The sender simply starts sending packets to the destination. If the destination is not receiver, the receiver become to sender and starts sending packets, till send exactly destination. Connectionless does not have the reliability. Therefore, connectionless must contain routing information. Connectionless data transport protocol does not require authentication, and has no error control process.

Client establishes communication with the server

Client makes a request from the server

The server provides an answer to the client

If a connectionless protocol such as UDP was used , the server disconnects and communication between client and server is lost.

If a connection-oriented protocol such as TCP/IP was used, the communication between the client and the server is not broken. The client can keep making requests from the server. Communication will be broken at the client's request.