TCP (Transmission Control Protocol) is
the most commonly used protocol on the Internet. The reason for this
is because TCP offers error correction. When the TCP protocol is used
there is a "guaranteed delivery." This is due largely in
part to a method called "flow control." Flow control
determines when data needs to be re-sent, and stops the flow of data
until previous packets are successfully transferred. This works
because if a packet of data is sent, a collision may occur. When this
happens, the client re-requests the packet from the server until the
whole packet is complete and is identical to its original.
UDP (User Datagram Protocol) is anther
commonly used protocol on the Internet. However, UDP is never used to
send important data such as webpages, database information, etc; UDP
is commonly used for streaming audio and video. Streaming media such
as Windows Media audio files (.WMA) , Real Player (.RM), and others
use UDP because it offers speed! The reason UDP is faster than TCP is
because there is no form of flow control or error correction. The
data sent over the Internet is affected by collisions, and errors
will be present. Remember that UDP is only concerned
with speed. This is the main reason why streaming media is not high
quality.
Frame Structure
As data moves along a network, various
attributes are added to the file to create a frame. This
process is called encapsulation. There are different methods
of encapsulation depending on which protocol and topology
are being used. As a result, the frame structure of these
packets differ as well. The images below show both the TCP and UDP
frame structures.
TCP FRAME STRUCTURE
UDP FRAME STRUCTURE
The payload field contains the
actually data. Notice that TCP has a more complex frame structure.
This is largely due to the fact the TCP is a connection-oriented
protocol. The extra fields are need to ensure the "guaranteed
delivery" offered by TCP.
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