What is TCP/IP, and how does it work?
5 min read
The TCP/IP model is a set of protocols that define how the internet as we know it today functions. It’s a collection of rules that defines the data transmission process, from breaking data into packets to addressing, transmitting, and routing it until the data reaches its destination. Read the article to find out how TCP/IP makes sure data smoothly travels over the internet.
Table of Contents
Table of Contents
What is TCP/IP?
Transmission Control Protocol/Internet Protocol (TCP/IP) is a network protocol suite that defines the requirements for safe and efficient data transfer online. This protocol is tasked with finding the destination IP address.
The TCP/IP interconnects network devices by breaking data into smaller packets, assigning each packet an IP address, and routing them through different networks to their destination. In this process, TCP is responsible for breaking down packets, sending them, and reassembling them at the destination, while IP makes sure the data is sent to the correct device.
Main differences between TCP and IP
TCP and IP are two core protocols that carry messages over the internet. IP assigns addresses to data packets and sends them to the correct destination, but it doesn’t guarantee delivery. In short, IP handles the “where” part. TCP, on the other hand, is responsible for the “how” part — it makes sure data packets get delivered safely and in the correct order.
Let’s compare the TCP and IP protocols:
| Feature | TCP | IP |
|---|---|---|
| Role | Reliable and ordered data transfer. | Correct data addressing. |
| Connection type | Establishes a connection before sending data. | Sends data packets without prior setup. |
| Reliability | Highly reliable (finds and resends lost data and makes sure all data packets arrive). | Less reliable (doesn’t guarantee the data will arrive). |
| Error handling | Detects errors and resends lost data. | Doesn’t handle errors and focuses on data routing only. |
| Data handling | Splits data into segments and reassembles them at the destination. | Divides data into packets and assigns addresses. |
| Use case | Used in applications that need reliable data transfer, for example web browsing and email. | Used in any internet communication. |
How does TCP/IP work?
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.
Four layers of TCP/IP
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.
Four layers of TCP/IP include:
- Application layer
- Transport layer
- Internet layer
- Datalink layer
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), Dynamic Host Configuration Protocol (DHCP), and Simple Network Management Protocol (SNMP).
Transport layer
As you might’ve guessed, the transport layer takes care of transporting data. It includes TCP as well as User Datagram Protocol (UDP). 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 Address Resolution Protocol (ARP), Internet Group Management Protocol (IGMP), and Internet Control Message Protocol (ICMP). 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 (the router) but also the correct device within that network (your phone connected to that router). This involves identifying the MAC address of the intended device and managing data transfer through the Ethernet cables and Wi-Fi.
TCP/IP vs. the OSI model
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 comprehensive, protocol-independent conceptual model. In other words, TCP/IP uses standardized protocols to address everyday communication 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 and transport layers serve identical roles 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.
To better understand the main differences between TCP/IP and the OSI model, take a look at this brief breakdown:
| Criteria | TCP/IP model | OSI model |
|---|---|---|
| Number of layers | Four layers. | Seven layers. |
| Layer names | Application, transport, internet, and datalink. | Application, presentation, session, transport, network, datalink, and physical. |
| Function | Transmits data over the internet. | Theoretical framework for data communication. |
| Standardization | Industry standard for internet communication. | A reference model for understanding network architecture. |
| Communication | Uses packet switching and routing for communication. | Emphasizes a strict top-down communication model. |
| Development model | Developed by the Department of Defense. | Developed by the International Standards Organization (ISO). |
| Use cases | Internet communication and networking. | A conceptual framework for teaching and designing networks. |
Advantages of the TCP/IP model
TCP/IP is popular for a reason — it offers numerous advantages when it comes to communications, such as:
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.- 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.
- 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.
- 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).
Disadvantages of the TCP/IP model
While popular, the TCP/IP model is by no means perfect — here are some disadvantages that you should be aware of:
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.- 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.
- 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).
- 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.
Is TCP/IP secure?
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 Pro™ feature. It helps you identify malware-ridden files, stops you from landing on malicious websites, and blocks trackers and intrusive ads on the spot.