What Is the Network Layer? Definition and Practical Applications

Key takeaways

• The network layer is an intermediary between layers that fosters internet communication and helps ensure data packets travel successfully and efficiently across interconnected networks.

• The network layer in the OSI model serves as a bridge between the data link layer and the transport layer.

• Physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer constitute the seven layers of the OSI model.

The network layer prioritizes certain types of traffic to ensure the timely delivery of critical data. Read this article to learn what network layers are, what they do, why they matter, the careers that use them, and how to get a role in networking.

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What is the network layer?

The network layer is one of seven layers that make up the larger communication process across the internet. It ensures the efficient and reliable transmission of data packets across interconnected networks, supports dynamic routing, establishes secure communication, and enables global connectivity. Its processes are critical for the proper functioning and performance of modern computer networks.

It serves as an intermediary between the data link layer (Layer 2) and the transport layer (Layer 4) in the open systems interconnection (OSI) model. Its primary purpose is to provide logical addressing, routing, and forwarding of data packets across networks.

At its core, the network layer establishes and maintains end-to-end communication between devices that connect to disparate networks. It accomplishes this by assigning unique addresses to each device, known as logical addresses. One widely used logical addressing scheme on the internet is internet protocol (IP) addressing.

The network layer encapsulates the data received from the transport layer into smaller units called packets. In addition to the data they carry, these packets include information such as the source and destination IP addresses, packet sequencing information, and error-checking codes.

Is Layer 3 the network layer?

Yes, Layer 3 is also called the network layer. IP, internet control message protocol (ICMP), address resolution protocol (ARP), and border gateway protocol (BGP) are among the key protocols associated with the network layer.

OSI model

The OSI model contains seven layers, each with a distinct set of duties for the communication system. Each layer interacts with the various layers above and below to facilitate smooth communication and data transmission. The OSI is the overall framework that outlines these responsibilities and functions. The seven layers of the model are as follows:

1. Physical layer

2. Data link layer

3. Network layer

4. Transport layer

5. Session layer

6. Presentation layer

7. Application layer

Overall, these seven layers work together to facilitate effective data transfer from device to device.

Network layer vs. internet layer

It is sometimes easy to confuse the network layer and internet layer and use the terms interchangeably, but they differ depending on which communication model is in context. The network layer refers to the third layer of the OSI model, which handles logical addressing and routing. It focuses on delivering data packets from the source to the destination across multiple networks.

The internet layer, meanwhile, specifically refers to the network layer in the TCP/IP protocol suite (another reference model of how the internet works). It is responsible for accepting and routing IP packets. Like the network layer, the internet layer in TCP/IP also plays a fundamental role in enabling global internetworking by connecting diverse networks into a unified inter-network, such as the internet.

Both of these layers serve the same purpose for the most part, but the network layer is present in the OSI model, while the internet layer is part of the TCP/IP model.

What does the network layer do?

The network layer performs several essential functions in a networking system, including addressing, routing, fragmentation and reassembly, quality of service, and error handling. Take a look at each in more detail:

• Addressing: The network layer assigns unique addresses to devices on a network, such as IP addresses. These addresses help identify the source and destination of data packets.

• Routing: It determines the optimal path for data packets to reach their destination across multiple networks. This involves analyzing routing tables, considering network conditions, and making forwarding decisions.

• Fragmentation and reassembly: When data packets are too large to fit into the maximum transmission unit (MTU) of a network, the network layer fragments them into smaller units at the source and reassembles them at the destination.

• Quality of service (QoS): The network layer can prioritize certain types of traffic, ensuring that critical data, such as real-time traffic, receives preferential treatment in terms of bandwidth and latency.

• Error handling: It can detect and correct errors in data packets using error detection and correction mechanisms.

What is a packet?

A packet is a unit of data that’s transmitted across a network. The packet consists of a header, a payload, and a trailer. The header contains control information, such as source and destination addresses, identifying value, and error-checking codes. Inside the payload is the real data being transmitted. The trailer contains information to inform the recipient device when it reaches the end of the packet.

Why is the network layer in the OSI model important?

The network layer plays a crucial role in the overall functioning of a computer network. A few reasons why it is important include:

• Addressing and routing: The network layer enables logical addressing, which allows devices to be uniquely identified on a network. It also determines the most efficient route for data packets to reach their destination, considering factors such as network congestion, reliability, and performance.

• Interconnectivity: The network layer facilitates the interconnection of different networks, enabling seamless communication and data transfer between devices and networks that may employ different underlying technologies.

• End-to-end delivery: The network layer ensures reliable end-to-end delivery of data packets across multiple networks. It handles packet fragmentation and reassembly, error detection and correction, and congestion control mechanisms to optimize data transmission.

• Network security: The network layer contributes to network security by implementing features such as virtual private networks (VPNs). These measures help protect data confidentiality, integrity, and availability during transmission.

Careers that use network layers and how to get started

Various careers in computer networking, systems engineering, and cybersecurity use and reference the network layer and the broader OSI model when working with the internet and determining the requirements for connecting multiple systems. These careers involve handling how computers and various systems communicate with each other. Popular jobs in computer networking that involve the network layer and the OSI model include:

• Computer technician

• Computer engineer

• Network administrator

• Network analyst

• Database administrator

• Network engineer

• Network security analyst

• Computer systems analyst

Read more: What Are Computer Information Systems? Definition, Degree, and Careers

How to enter a networking career

To prepare for one of these roles in computer networking, ensure you have the proper education. Typically, professionals in these careers have at least a bachelor’s degree in a related discipline, such as IT or network operations and security. Completing a degree in one of these fields exposes you to important topics related to these jobs, such as networks and security, programming, cybersecurity, and various fundamentals of information technology.

If your goal is to pursue more advanced or senior roles within the field of computer networking, a master’s degree in a related subject is an option for you as well. You can also prepare for your career outside of formal education by earning relevant certifications. These credentials show potential employers that you have the skills needed to perform in a computer networking role effectively. They also allow you to build experience with the necessary tools and systems professionals use. Some certifications to consider include:

• CompTIA Network+: This certification verifies that you have a solid background in various networking concepts and network security.

• CCNA Certification: This credential from Cisco validates your knowledge of networking fundamentals, network security, and IP protocols.

• ITIL 4 Foundation: While preparing for this certification from Axelos, you can familiarize yourself with key IT and digital service delivery concepts.

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