These services are used for transferring of data between the two host computers.
In the connection oriented service, the two computers or end systems, who want to send data to each other, start their communication via using a handshaking system. It means that firstly the sender computer sends a control packet to the other end system, in this packet there is not any data; it's just for the establishment of connection between two computers. When the other computer sends the acknowledgement packet back to the first computer then their connection is established and after that first computer sends it data to the other end system. The purpose of sending the control packet is to tell the other system that is ready, I am sending data. So the other system accepts the data without any delay. That's why it is called connection oriented service. It is mostly used by the TCP. This service is slow because of handshaking process but it is reliable, chances of data loss are very less.
The connection-less service is without any handshaking process. If one computer wants to send the data then, it just sends the data packet to the end system. This service is used in the UDP. This type of service is fast then the connections oriented service but the data loss chances are more.
Understanding connection oriented and connectionless service can become easier if we consider examples in the daily life.
The most common example for the connection oriented service is the PSTN (Public Switched Telephone Network), the analogue phone system that you use every day.
In connection oriented system such as the PSTN, a direct connection is laid between you and the person at the other end. Therefore, if you called from Canada to Pakistan for 10 minutes, you are in reality actually the owner of that copper wire for the whole 10 minutes.
This inefficiency however overcame by the multiple access techniques invented.
In direct contrast to connection oriented service, connection less oriented service doesn't require a direct connection to be setup. A daily example would be the internet which uses the IP technology for providing connection less services.
In connection oriented services, data is basically divided into several packets and each packet is given the address and the number. In connection less service, the data can take any path to reach its destination. A very good example for this can be VOIP (Voice Over Internet Protocol).
When all this is said and done, Connection less service seems to be unreliable service and people still don't rely on it and use it as a secondary way for communication than the common PSTN service. The reason being is that PSTN is more reliable, the quality more better which suits the business people more than the cheap connection less services.
However, the change from connection to connection less service is inevitable.
* Connection-oriented Requires a session connection (analogous to a phone call) be established before any data can be sent. This method is often called a "reliable" network service. It can guarantee that data will arrive in the same order. Connection-oriented services set up virtual links between end systems through a network, as shown in Figure 1. Note that the packet on the left is assigned the virtual circuit number 01. As it moves through the network, routers quickly send it through virtual circuit 01.
* Connectionless Does not require a session connection between sender and receiver. The sender simply starts sending packets (called datagrams) to the destination. This service does not have the reliability of the connection-oriented method, but it is useful for periodic burst transfers. Neither system must maintain state information for the systems that they send transmission to or receive transmission from. A connectionless network provides minimal services.
Connection oriented is in which connection is connected in between the 2 or more network.and connection less services is just like wireless applications.
Connection oriented means that a connection must be established before sending the data from one point (end) to other end between two bodies. Connection oriented service gives the guarantee that data must be reached at the other end without any errors and duplication. The advantage of this service is that if due to some reasons data does not reached at the other end then the sending body knows that and can resend the same data. TCP (Transmission Control Protocol) is a connection oriented protocol and used for communication.
On the other hand Connectionless service does not provide the guarantee that data will reach on the destination without errors. By using this service no need to establish a connection before sending data and that's why if we lose data some where between the communicating bodies then neither sender nor receiver can know about data lose. Data send by using connectionless service, some times reach at the destination with duplicate contents. Bust still user Datagram protocol is used in many applications especially in those applications where video is used. Because it does not require the establishing a connection before sending the data and that's why those applications which use videos such as sharing video between two bodies, UDP is considered better than TCP.
A connection oriented service responds to connections between a sending and receiving station and acknowledges the connection. A connectionless service does not establish the connection. A connectionless service does not have flow and error control. A connection oriented service is reliable, a connectionless service is fast.
Connection-oriented refers to an organization of communication between end systems, where you may have a protocol which is based upon persistent connections. Connectionless service refers to the property of an internal network where data is passed without the maintenance of a persistent connection.
Connection oriented service refers to the connection which reserves path and resources before transferring the data while connectionless does not reserves path or resources while transferring the data from one end to another end.
Connection-Oriented vs. Connectionless Service
This characteristic specifies whether conversations take place in a more or less structured manner. When using a connection-oriented protocol, you incur the overhead of setting up a virtual circuit (a defined communications path) between the sender and receiver, which is maintained until the sender and receiver have completed their entire conversation.
When the conversation is completed, you incur the overhead of tearing down the virtual circuit. Connection-oriented protocols provide guaranteed delivery of messages in the order in which they were sent.
Contrast this with Connectionless service, which does not require establishing a session and a virtual circuit. This can be found in the network layer or transport layer, depending on the protocol. You can think of a connectionless protocol as being akin to mailing a post card. You send it and hope that the receiver gets it. Common features of a connectionless service are:
O Packets do not need to arrive in a specific order
o Reassembly of any packet broken into fragments during transmission must be in proper order
o No time is used in creating a session
o No Acknowledgement is required.
The largest connectionless network in use today is the Internet.
This is the good differences b/w connection and connectionless services