What Is the Network Layer? Definition and Practical Applications

Key takeaways

The network layer is one of seven layers that make up the larger communication process across the internet.

• The network layer enables end-to-end communication by assigning logical addresses and routing data packets across interconnected networks.

• The essential functions of the network layer include addressing, routing, fragmentation and reassembly, quality of service (QoS), and error handling.

• You can strengthen your networking career by building core information technology (IT) knowledge and pursuing credentialing programs to validate your skills and improve job readiness. 

Explore what network layers are, what they do, and why they are important, as well as careers that use network layers and how you can obtain a role in networking. Then, if you’re ready for a career as an IT support specialist, consider enrolling in the IBM IT Support Professional Certificate program. In as little as three months, you can master the most up-to-date practical skills and tools used by IT support professionals.

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 the dynamic routing of networks, establishes secure communications, and enables global connectivity. Its processes are critical for the proper functioning and performance of modern computer networks.

The network layer is a critical component of the networking architecture that operates at the third layer of the Open Systems Interconnection (OSI) model. It serves as an intermediary between the data link layer (Layer 2) and the transport layer (Layer 4) in the 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.

OSI model

The OSI or Open Systems Interconnection 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 act together to facilitate data transfer from device to device effectively.

Is layer 3 the network layer?

Yes, network 3, the internet protocol, is also called the network layer.

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 identify and amend errors in data packets through 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 computer networks 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 utilize and reference the network layer and the broader OSI model when dealing with the internet and determining the requirements to connect multiple systems. These careers all relate to network communications and computer networking and 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. Most 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 you’ll need 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 helps you build knowledge in networking fundamentals, network security, and IP protocols.

• ITIL 4 Foundation: With this certification from Axelos, get an introduction to key IT and digital service delivery concepts.

Stay current on IT trends 

Eager to grow your expertise? Keep up with the latest trends and in-demand skills in your industry by subscribing to our LinkedIn newsletter, Career Chat To continue exploring IT and networking careers, concepts, and courses, check out these free resources:

• Access online glossaries: Information Technology (IT) Terms: A to Z Glossary

• Hear from a pro: Meet the IT Support Tech Advancing Toward a Cybersecurity Career

• Watch on YouTube: How to Get an IT Job (No Experience Needed)

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