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UDP - User Datagram Protocol
The second
protocol used at the Transport layer is
UDP. Application developers
can use UDP
in place of TCP.
UDP is the scaled-down
economy model and is considered a thin protocol.
Like a thin person in a car, a thin protocol doesn't
take up a lot of room - or in this case, much bandwidth
on a network.
UDP as mentioned dosen't
offer all the bells and whistles of TCP, but it does a
fabulous job of transporting information that doesn't
require reliable delivery and it does so using far fewer
network resources.
Unreliable Transport
UDP is considered to be an
unreliable transport protocol. When
UDP sends segments over a
network, it just sends them and forgets about them. It
doesn't follow through, check on them, or even allow for
an acknowledgment of safe arrival, in other words ....
complete abandonment! This does not mean that
UDP is ineffective, only
that it doesn't handle issues of reliability.
The picture
below shows us the UDP
header within a data packet. This is to show you the
different fields a UDP
header contains:
Connection-less Oriented
For those
who read about TCP, you
would know it is a connection oriented protocol, but
UDP
isn't. This is because UDP
doesn't create a virtual circuit (establish a connection
before data transfer), nor does it contact the
destination before delivering information to it. No
3-way handshake or anything like that here!
Since
UDP assumes that the
application will use its own reliability method, it
doesn't use any, which obviously makes things transfer
faster.
Less Overhead
The very
low overhead, compared to TCP,
is a result of the lack of windowing or acknowledgments.
This certainly speeds things up but you get an
unreliable (in comparison to
TCP) service. There
really isn't much more to write about
UDP so I'll finish here.
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