Connectionless
communication is a fast way to send information to a destination;
however, it is not reliable because there is no notification of
receipt to the source location. Connectionless protocols include IP
and IPX (layer 3) and UDP (layer 4).
Connection-oriented protocols include
TCP (layer 4) and SPX. Connection-oriented protocols, such
as TCP, typically use an acknowledgement (ACK) process between
source and destination. If a source does not receive an ACK from the
destination, TCP will retransmit the segment until an ACK is
received. The processes of segmentation,
handshaking/acknowledgement, flow control, and error checking are
used to provide reliable transport.

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