A connection-oriented protocol is one where a logical connection is first established between devices to data being sent. The connection-oriented service has several other services combined package. Such as:
Reliable Data Transfer
Flow Control
Congestion Control
Reliable Data Transfer means, it sends data to receiver reliably. How can we know that the data has reached? When we will get an acknowledgement from receiver. If we not get ACK then the missing data should be retransmit, what we have seen in Stop &Wait Protocol, Go Back N, Selective Repeat protocol.
TCP is a connection-oriented protocol. It takes the best part of Go Back N and Selective Repeat. It buffers like selective repeat at the receiver end. Sender does not send too much data that overflow in buffer at receiver. This controlling process is called Flow Control.
If a channel can transmit 4 packet at time but there are 5 packets passing though the channel so data can be lost. This is called Congestion. In the late 1980, TCP implemented Congestion Control.
Another things happen that when sender send data to receiver it makes a connection with server. Sender sends a message for connection. Server reply. If yes then start to send data. This procedure is called Three-way Handshake.
Connection-less Protocol:
On the other hand connection-less protocol has no handshaking procedure, no Flow Control, no Congestion Control and it sends unreliable data which has no acknowledgement from receiver. This protocol is UDP (User Datagram Protocol).
Then why we use UDP? With the disadvantages come some advantages. UDP is a very simple protocol. If a process wants to send a small message and does not care much about reliability, it can use UDP. Such as Video and Audio data.
In 28th August 1980 J. Postel defined about UDP.
Use of UDP:
• UDP is suitable for a process that requires simple request-response communication with little concern for flow and error control. Such as FTP needs to send bulk data. (Later we will know about FTP).
• UDP is suitable for a process with internal flow and error-control mechanisms. For example TFTP process includes flow and error control. It can easily use UDP. (Later we will know about TFTP).
• UDP is used for management processes such as SNMP. (Later we will know about SNMP).
• UDP is used for some route updating protocols such as RIP. (later we will know about RIP)
• UDP is suitable transport protocol for multicasting. Multicasting capability is embedded in the UDP software not in the TCP software.
Checksum:
UDP provides error detection by checksum. It does not do anything to recover from an error. Some implementations of UDP simply discard the damaged segment. And other implementations of UDP pass the damaged segment to the application with a warning.
Now we will learn a little about TCP
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