Connection Oriented Service:

• TCP is a transport layer protocol which provides connection oriented service.
• In this connection is created, maintained and once the data sent is successful, connections is terminated.
• Since connection is established, there is a relationship among each bytes(5 tuples are same for all), they are not independent, hence take the same path to reach the destination.
• Here packets(segments) are numbered that is each bytes has a sequence number and hence do not reach out of order( reassembly because of sequence number).
• It is stream oriented that is continuous flow of data(phone call) and needs authentication.
• There is a flow and error control mechanism like support of acknowledgement number.
• There is also support of congestion control.
• Because of all above characteristics, connection oriented service are reliable.

Connectionless service:

• UDP is a transport layer protocol which provides connectionless service.
• In this case there is no connection establishment or connection terminated.
• There is no relationship between the different datagram, that is they are independent.Since each datagram are independent and not numbered, they can take different path to reach to destination.
• It is message oriented that is message are chopped and send in distinct chunks and groups and such message does not need authentication. Example: Any chat application
• There is no error control except for the checksum. It does not have acknowledgement for the received datagram.
• It also does not have congestion control mechanism.
• It is not as reliable as connection oriented service.

Categories: Networking