What is a connection oriented service?

To send the data from one device to another device there should be a connection. The connection can be established to transfer data between the devices can be done in two ways and they are as follows −

  • Connection Oriented Service

  • Connectionless Services

Now let us discuss the Connection oriented services.

Connection Oriented Services

For the connection oriented service, the user has to follow the sequence operations given below −

  • Connection is established

  • Information is sent

  • Connection is released

We have to establish a connection before starting the communication in connection oriented service. Whenever the connection is established we can send the message and after that we can release the connection.

Connection oriented service is more reliable than connectionless service. In connection oriented service we can also send the message if there is an error at the receiver’s end. For example: connection oriented is TCP protocol.

In connection-oriented services, the devices at both the endpoints use a protocol to establish an end-to-end connection before sending any data.


The characteristics of Connection-oriented service are as follows −

  • There is a network guarantee in connection oriented service that all packets can be delivered in order without loss or duplication of data.

  • All the data follows in a single path where the connection is established.

  • There is a network guarantee for a minimal amount of bandwidth which is reserved for the duration of the call.

  • The over utilization of the network, leads to refusing the future call request.

  • Sometimes we call Connection-oriented service as reliable network service because it guarantees the data should arrive in the proper sequence. Single connection for the entire message facilitates acknowledgement process and retransmission of damaged and lost frames.

Stages for Connection-oriented Transmission

There are three stages for Connection-oriented transmission which are as follows −

Connection establishment

Before transmitting data in connection oriented, the sending device has to determine the availability of the other device to exchange data and a connection has to be established by which data can be sent.

Generally the Connection establishment requires the following three steps −

  • First sender computer requests the connection by sending a connection request packet to the intended receiver.

  • After that, the receiver computer returns a confirmation packet to the requesting computer.

  • Finally, the sender computer returns a packet acknowledging the confirmation.

Data transfer

The sender starts sending data packets to the receiver after the connection is established.

Connection termination

When all the data gets transferred, the connection has to be terminated. This connection termination requires a three-way handshake.

  • First, the sender computer requests disconnection by sending a disconnection request packet.

  • After that, the receiver computer confirms the disconnection request.

  • Finally, the sender computer returns a packet acknowledging the confirmation.

Transmission Control Protocol (TCP) is a connection-oriented protocol.


There are four types of Connection Oriented Service primitives which are as follows −

  • CONNECT − This primitive makes a connection.

  • DATA, DATA-ACKNOWLEDGE, EXPEDITED DATA − Data and information is sent using this primitive.

  • CONNECT − Primitive for closing the connection.

  • RESET − Primitive for resetting the connection.

Updated on: 17-Mar-2022

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