07: Transport layer - UDP header (User Datagram Protocol) part 8

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This  lesson comes after a thorough, well-thought-out explanation of the TCP header which I highly recommend for everyone to go through on the grounds of the detailed and valuable networking concepts it contains. The TCP header is a connection-oriented protocol ; otherwise, UDP is a connectionless protocol, which is our point of interest in this lesson.  The header of the UDP lacks nearly all the good characteristics of the TCP header. Notwithstanding differences, there are still things that these two protocols have in common.

Having less fields than TCP header does not mean that UDP is useless. UDP has also a very important role in data transmission, it is much faster than TCP. UDP is usually used in the transmission of data that needs to be transfered too fast. The following is the UDP header along with its fields.

As you see, UDP header contains only few fields compared to TCP. Speed in data transmission if the aim of UDP header.  There is no need to explain those fields again because they are already dissected in the previous lesson (see the Transport layer’ parts). However, it would be much helpful to compare and contrast UDP and TCP header.

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TCP (Transmission Control Protocol)	UDP (User Datagram Protocol)
Connction-oriented protocol	Connectionless protocol
It assures reliable delivery of data to the DST	Data delivery is not guaranteed
The speed is slower	faster because there is error checking for data
The size of the header is 20 Bytes	The header’s size is 8 Bytes
It rearranges data segments when it arrive in a disorderly way	It does not rearrange data. It is received as it is sent
Source port, Destination port, Checksum	Source port, Destination port, Checksum
It establishes a connection before data transmission, it also closes the connection after data transmision	It is not connection based, that is, an application can send a load of data to another application program without opening,(no three-way handshake) maintaining, or closing a connection
It is suitable for applications that require high reliability, and transmission time is relatively less critical	It is suitable for applications that need fast, efficient transmission, such as games.
It is heavy-weight	It is light-weight
Flow control is supported	There is no flow control

The above contrast and comparison of UDP and TCP gives the reader all what he/she needs to know about these two protocols. So, UDP is to be equated with speed in transmission, whereas TCP is to be identified with reliablity in data transmission.
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