When working with networking, you'll quickly encounter the terms TCP & UDP, but what do these terms mean?
Both TCP and UDP are network protocols, used to transfer bits of data (so called packets) over the internet. The TCP and UDP protocols opperate on top of the regular internet protocol (i.e. in the transport layer/application layer in the IP-stack).
TCP
TCP stands for Transmission Control Protocol and is most commonly used; if you click a link on a website from your own computer for example, your browser sends TCP packets over the internet to the server which hosts the website in question, which in turn sends TCP packets back to your computer.
TCP assigns each packet a number, so the recipient receives the packets in the correct order. TCP also checks the data which is being transfered, so the receiving server also sends messages back to the sender to confirm that it has received the packets and that they contain no errors. Does the server send the wrong reply back to your computer? Then the packets are send again by your computer.
Besides webtraffic, TCP is for example also used for downloading files and the streaming (not live) of video
UDP
UDP stands for User Datagram Protocol, where a Datagram is the same as a packet. UDP works the same as TCP, but without the two way error checking which TCP performs. As a result, UDP is faster than TCP, but also less reliable in sending data.
Because of this, UDP is mostly used when speed is more important than a 100% error free connection. This is for example the case when sending data about server availability, live voice and video streaming and online gaming.
TCP traffic as such is two way traffic, where mainly the error free transfer of data is the most important aspect, where UDP is one way traffic, where speed is prioritized.
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