What is TCP, UDP, IP, IP Address and Subnet Mask

Transmission Control Protocol (TCP)

Transmission Control Protocol (often shortened to TCP) is set of rules which pair up with other sets of rules when sending data between computers locally or over the internet. It is one of the most common protocols used when using the internet alongsideIP, and is used by web browsers when they connect to the internet.


When data (such as an HTML internet page for example) is sent between computers, TCP divides it up into individual units, called data grams or packets – this ensures they arrive efficiently and are tracked safely from one computer to another. TCP is responsible for breaking the data being sent down into these packets, and then reassembling them in the correct order at the other end so they make sense again. The actual delivery of the data is handled by another set of protocols.

TCP is also responsible for checking packets for errors, and if it detects them, lets the user on the receiving end that mistakes may be present in the presentation of their data. TCP relies on a steady and continuous connection to work properly, which must be present during the entire process of breaking down, checking, and reassembling the data packets to be sent.

  • User Datagram Protocol (UDP)

User Data gram Protocol (often shorted to UDP) is another set of rules used when sending data between computers locally or over the internet. It is used as an alternative to TCP and often in conjunction with IP. This protocol, like TCP, is responsible for ensuring data that is being received is the same as the data that was sent, however it does not break data down into packets in order to do so. This means that UDP is not responsible for the data arriving in the correct order when sent, instead this must be handled by a separate application in the receiving computer.

UDP is therefore very efficient and fast, but not necessarily always reliable as it cannot guarantee that the data which arrives is presented correctly, and cannot inform users that mistakes may be present. UDP may be preferred by users who have only tiny amounts of data to send and wish for it to arrive quickly and efficiently, however for larger amounts of data, TCP is generally preferred. UDP is a much simpler set of rules, and works well for some purposes since it does not create delays.

  • Internet Protocol (IP)

Internet Protocol (often shortened to IP) is the foremost set of rules for communicating over the Internet, which essentially establishes how the internet is able to function. It is usually combined with a number of other protocols in order to communicate data and connect two hosts (computers) together so they are able to share data between them, either privately or publically.

IP is responsible for the actual delivery of data, which is sent from one computer to another via a series of stopping points called gateways. These gateways recognize the data and send it on to a subsequent gateway, and so on until the data arrives at its final intended destination. Data can get mixed up and sent in the wrong order, but IP does not deal with this.


Instead TCP or an application is responsible for checking this and setting it right again. IP does not rely on a direct communication between two computers, rather the gateways treat each piece of data as a unique unit to be processed as its own entity. All IP is responsible for is getting the data from A to B in one piece, which it can do very reliably.

  • IP Address

An IP Address is a unique number assigned to each and every device which is participating in a network. A device could be a computer, a printer, or anything else which connects to either a local network or the internet. All computers connected to the internet use IP Addresses when communicating with each other.

IP Addresses are made up of Binary Code, but are displayed in numbers so humans are able to read it. These are usually groups of numbers separated by dots, for example 216.27.41.187. There are several types of IP Address, such as IPv4 and IPv6, the latter of which is newer and becoming more popular as it is able to create more unique addresses, allowing more people than ever before to use the internet. IP Addresses can be static, meaning they are created by the user themselves, or dynamic, meaning they are assigned automatically by the network – dynamic is by far the most common.

Your IP address gives information about your device’s geographical location, and the location of the server you are closest to and use most often. This is most often used by law enforcement to track users who are breaking the law online.

  • Subnet Mask

A subnet splits up the traffic on a network into smaller, more manageable, logical groups. This can allow for improvement in the network’s performance and security. A subnet mask is a binary code which is formatted similarly to an IP Address, eg. 227.87.34.972. An IP address generally gives information about the network overall and the specific device being used, however when a Subnet Mask is used alongside it the information provided by the IP Address is further extended to also provide information about the subnet being used.

This can be useful to very large networks, for example a large multinational company’s internal network, as it can help avoid delays and confusion when transferring data. The Subnet Mask provides clear information to the gateways within the network so they know exactly where to send each piece of data that is transmitted without any delays or hesitations.

They can also be used to provide additional security by obscuring network information in publically view able IP Addresses.  Subnets can be used to limit user’s access to certain parts of the network in desirable ways, or filter incoming traffic efficiently between different subnets to reduce overall stress on the network.

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