A connection-oriented communication is a data communication mode that requires an overhead in setting up a request for connection before sending any type of data communication message. The connection-oriented mode (CO-mode), as differentiated from connectionless communication, is required by most computer networking protocols to ensure no packets are missed. Protocols are a set of standards and rules that support specific modes of data communications. The connection-oriented communication was designed to make sure that there are resources available as required by the type of communications being requested.
Connectionless communication is a best-efforts type of communication. For instance, user datagram protocol (UDP) is transmitted to a destination without any previous data exchange. There could be an application in the destination computer that awaits the UDP packet. The UDP packet is received and the data are extracted. No mechanism will ask the source computer to retransmit the packet in case the packet never reaches the destination as an error-free packet.
Packet switching allows a large amount of data to be sent as several packets over the Internet into a destination computer. The connection-oriented communication tracks the status of the source and destination computers, and the completion of data transfer. More packets may still be required to complete the data transfer.
Layer 1 in the open systems interconnection (OSI) model is the physical layer that determines if the physical medium is wire, wireless, or optical fiber. The second layer defines how the data nodes like computers and routers are able to determine when to transmit. Layer 3 determines the network addressing and how packets reach the required destination address in a public data network. It is the transmission control layer that handles the pacing of data transmission. Layer 4 is where connection-based or connectionless communication is determined.
Buffers on destination equipment may be filled up and protocols such as the transmission control protocol (TCP) will signal the source computer to temporarily stop sending data. The TCP also retries the completion of data transfers when these are interrupted. In packet switching, the TCP makes sure that the packets are in the right order even if some are late in reaching the destination. The TCP, which is the connection-oriented communication, tracks data transfers, and controls pacing, error checking, and possible retransmission to make sure that data transfer is successful. The UDP is connectionless, on the same layer in the OSI model as the TCP, and used by applications that can make do without tedious managements.
Statistical multiplexing is a useful process of sharing high-speed data and balancing data transfer requirements on several input/output ports. In a geographically remote area, a statistical multiplexer may connect this area to the rest of the Internet. This statistical multiplexer makes it possible for single data communications hardware to and from that area to be shared by many users. It provides a separate virtual circuit, but is using only one physical circuit, which is the combined or aggregate link of the statistical multiplexer.