Transport Protocols
Traffic that traverses a network always has a source and destination address. This communication
is based on the seven layers of the OSI reference model. Layers 5 through 7 (the upper
layers) handle the application data, and Layers 1 through 4 (lower layers) are responsible for
moving the data from the source to the destination. The data is created at the application
layer (Layer 7) on the source machine. Transport information is added to the upper-layer
data, and then network information is added, followed by data-link information. At this
point, the information is transmitted across the physical medium as electronic signals.
The upper-layer data combined with the transport information is called a segment. As soon
as the network information is added to the segment, it is called a packet. The packet is
encapsulated at the data link layer (Layer 2) with the addition of the source and destination