What is TCP/IP and how does it work?

Remember sending letters? If you wanted to use the postal service, you had to write down a name and address on an envelope, according to the rules. You had to use a certain number of stamps and drop the letter into a letter box. Then there were even more regulations governing how the postal workers handled your mail.

The internet doesn’t require stamps, but it does have rules. The TCP/IP model is a comprehensive set of protocols that define how the internet as we know today functions.

TCP/IP is a network protocol suite that defines the requirements for safe and efficient data transfer online. TCP is short for Transmission Control Protocol, which is responsible for data delivery from one device to the other. IP stands for Internet Protocol. This protocol is tasked with finding the destination IP address.

TCP/IP works according to the client-server communication model, where the client device receives services from a server device. The main function of TCP/IP is to accurately transmit messages between devices over a network.

For maximum accuracy, messages are broken down into data packets (small bits of information with headers attached to steer them through the network). If any individual packets are corrupted en route, there’s no need to resend the whole message — the system simply sends the requisite packet again.

The TCP/IP model is responsible for transferring data between two devices. Why only two? Well, unlike radio, internet data isn’t just broadcast to whoever is listening. Even when hundreds of computers are sharing data at the same time, only two devices participate in any given data exchange.

TCP/IP protocols operate on four layers. This system is how the TCP/IP model ensures that different devices and apps can “communicate” and transfer data efficiently.

Application layer

The top layer includes the application layer protocols. It’s the easiest layer for users to interact with since these protocols are built into their apps (hence the name). Mail programs have SMTP, or Simple Mail Transfer Protocol, Internet browsers use HTTP, or Hypertext Transfer Protocol, and so on. Other common application layer protocols include FTP (File Transfer Protocol), DHCP (Dynamic host Configuration Protocol), and SNMP (Simple Network Management Protocol).

Transport layer

As you might’ve guessed, the transport layer takes care of transport. It includes TCP as well as UDP (User Datagram Protocol). UDP is simpler than TCP and is commonly used by real-time applications that don’t need to be as secure as other kinds of data.

TCP establishes the connection between the two networks and chops up the data into smaller pieces (packets) for efficiency. TCP also adds the assembly rules to each packet so the data can be put back together in the correct order after the transfer is complete.

Internet layer

Internet layer protocols include IP as well as ARP (Address Resolution Protocol), IGMP (Internet Group Management Protocol), and ICMP (Internet Control Message Protocol). The Internet layer manages the movement of data packets between the networks.

Datalink layer

The Datalink layer is the deepest layer of data transfer and can also be called the network interface layer. The job of this layer is to make sure that data not only arrives at the intended IP address (i.e., the router) but also the correct device within that network (i.e., your phone, which is connected to said router). This involves identifying the MAC address of the intended device and managing data transfer through the Ethernet cables and Wi-Fi.

There are various different types of IP addresses. An IP address can be public or private, and static or dynamic. So does TCP/IP work with all types of IP address? Yes! Whatever internet protocol your machine happens to use, it will still work as part of the TCP/IP data transfer process.

By far the easiest way to find your TCP/IP address is to google “What’s my IP address?” However, it won’t work if you are trying to find the IP address of a specific device within your network.

To find the IP of a device, like a network printer, try going to your network settings and looking for IPv4. Unfortunately, these are not universal instructions because every operating system has its own layout.

While both play important roles in data communications over the internet, TCP/IP and IP are different in that the former is a protocol stack (a collection of protocols for a specific purpose) while the latter is a low-level individual protocol. In fact, TCP/IP even makes use of IP for transporting data packets — but in addition, it connects devices and servers together.

By itself, IP is limited to data packets between 20 and 24 bytes long — larger pieces must be sent in multiple packets and assembled on delivery. This is not always efficient, because a separate data request is required for each packet. In contrast, TCP/IP sends all of the data at once, running checks both before and after delivery to make sure everything’s in one piece. TCP/IP also observes the network for congestion when routing data.

The difference between TCP/IP and OSI is the difference between practice and theory — TCP/IP is a practical protocol suite, while OSI is a protocol-independent conceptual model. In other words, TCP/IP uses standardized protocols to address everyday communications challenges, while OSI provides an overarching framework for multiple communication methods.

Both the TCP/IP and OSI models use layers to categorize operations, with considerable overlap in functionality — for example, the network layer and the transport layer serve an identical role in both models. However, while the TCP/IP model is composed of only four layers, the OSI model has seven. TCP/IP headers are also 20 bytes in size, while OSI headers use only 5 bytes.

However, TCP/IP and OSI have fewer differences than similarities. Both are logical models that use layered systems to define how data packets travel through networks.

TCP/IP is popular for a reason — it offers numerous advantages when it comes to communications, such as:

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  It works between different manufacturers’ devices and software. Because TCP/IP is a suite of standardized protocols, it allows different machines to seamlessly communicate with each other. The specifications of TCP/IP model protocols are available publicly, so it is fairly simple to implement compatible solutions.
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  It is globally accepted. TCP/IP is popular because it is useful — and at the same time, it is useful because it is popular. TCP/IP forms the foundation of the Internet, and its global prevalence allows devices everywhere to communicate with each other.
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  It is highly scalable. The ability to easily add new services and devices to existing infrastructure is key to expanding networks — including the biggest one of all, the internet.
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  It is flexible. The TCP/IP model is not tied to any specific type of physical network — in fact, it can easily adapt to various types of network technologies (like Ethernet and Wi-Fi).

While popular, the TCP/IP model is by no means perfect — here are some disadvantages that you should be aware of:

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  It is complicated to set up. The TCP/IP model is flexible and scalable — provided you know what you’re doing. The layered architecture can make it difficult to troubleshoot issues.
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  It consumes more bandwidth than many other models. TCP/IP adds extra headers and acknowledgments to each data packet to ensure stable communications, waits for confirmation of receipt, and retransmits lost or corrupted packets. While these measures make TCP/IP reliable, they also increase latency and bandwidth consumption.
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  It is not optimized for small networks. TCP/IP was originally designed for wide area networks (WAN). As a result, it is not suitable for local area networks (LAN) and personal area networks (PAN).
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  It is not forward facing. TCP/IP is a robust model, but it is also resistant to change. Because it does not clearly separate the concepts of services, interfaces, and protocols, TCP/IP struggles when it comes to describing new technologies in new networks.

One important thing to note is that TCP/IP is never private. Companies can collect, identify, and track IP addresses that go through their servers. And remember, every time you go online, your internet service provider (ISP) can see what you’re doing and can sell your private browsing history to third-party advertisers.

One way to avoid that is by using a VPN. While TCP/IP protocols do their thing, NordVPN will encrypt and reroute your traffic through a VPN server. So while you continue to browse safely, your ISP won’t be able to log your data and see your IP address.

NordVPN also has the Threat Protection feature. It helps you identify malware-ridden files, stops you from landing on malicious websites, and blocks trackers and intrusive ads on the spot.