What is computer networking?

Networked devices rely on communications protocols—rules that describe how to transmit or exchange data across a network—to share information over physical or wireless connections.

Before contemporary networking practices, engineers would have to physically move computers to share data between devices, which was an unpleasant task at a time when computers were large and unwieldy. To simplify the process (especially for government workers), the Department of Defense funded the creation of the first functioning computer network (eventually named ARPANET) in the late 1960s.

Since then, networking practices—and the computer systems that drive them—have evolved tremendously. Today’s computer networks facilitate large-scale inter-device communication for every business, entertainment and research purpose. The internet, online search, email, audio and video sharing, online commerce, live-streaming and social media all exist because of advancements in computer networking.

Before we delve into more complex networking topics, it’s important to understand fundamental networking components, including:

• IP address: An IP address is the unique number assigned to every network device in an Internet Protocol (IP) network; each IP address identifies the device’s host network and its location on the network. When one device sends data to another, the data includes a “header” that includes the IP addresses of both the sending and receiving devices.

• Nodes: A node is a network connection point that can receive, send, create or store data. It’s essentially any network device—computers, printers, modems, bridges or switches—that can recognize, process and transmit information to another network node. Each node requires some form of identification (such an IP or MAC address) to receive access to the network.

• Routers: A router is a physical or virtual device that sends data “packets” between networks. Routers analyze the data within packets to determine the best transmission path and use sophisticated routing algorithms to forward data packets until they reach their destination node.
  

• Switches: A switch is a device that connects network devices and manages node-to-node communication across a network, making sure that data packets reach their intended destination. Unlike routers, which send information between networks, switches send information between nodes within a network.

  Consequently, “switching” refers to how data is transferred between devices on a network. Networks rely on three main types of switching:

  • Circuit switching establishes a dedicated data communication path between nodes in a network, so no other traffic can traverse the same path. Circuit switching sees to it that full bandwidth is available during every transmission.

  • Message switching sends whole messages from the source node to the destination node, with the message traveling from switch to switch until it reaches the destination.

  • Packet switching involves breaking down data into independent components to make data transmission less demanding of network resources. With packet switching, packets—instead of entire data streams—travel through the network to their end destination.

     

• Ports: A port indicates a specific connection between network devices, with each port identified by a number. If an IP address is analogous to a hotel address, then ports are the suites and room numbers. Computers use port numbers to determine which application, service or process should receive which messages.

• Gateways: Gateways are hardware devices that facilitate communication between two different networks. Routers, firewalls and other gateway devices use rate converters, protocol translators and other technologies to make inter-network communication possible between otherwise incompatible devices.
  

Typically, computer networks are defined by geographical area. A local area network (LAN) connects computers in a defined physical space, while a wide area network (WAN) can connect computers across continents. However, networks are also defined by the protocols they use to communicate, the physical arrangement of their components, how they manage network traffic and the purpose they serve in their respective environments.

Here, we’ll discuss the most common and widely used computer network types in three broad categories.

The network types in this category are distinguished by the geographical area the network covers.

Network nodes can send and receive messages using either wired or wireless links (connections).

Computing networks can transmit data using a range of transmission dynamics, including: 

Computer network architecture establishes the theoretical framework of a computer network, including design principles and communications protocols.

• Peer-to-peer (P2P) architectures: In a P2P architecture, two or more computers are connected as “peers,” meaning they have equal power and privileges on the network. A P2P network doesn’t require a central server for coordination. Instead, each computer on the network acts as both a client (a computer that needs to access a service) and a server (a computer that provides services to clients). Every peer on the network makes some of its resources available to other network devices, sharing storage, memory, bandwidth and processing power across the network.

• Client-server architectures: In a client-server network, a central server (or group of servers) manages resources and delivers services to client devices on the network; clients in this architecture don’t share their resources and only interact through the server. Client-server architectures are often called tiered architectures because of their multiple layers.

• Hybrid architectures: Hybrid architectures incorporate elements of both the P2P and client-server models.

Whereas architecture represents the theoretical framework of a network, topology is the practical implementation of the architectural framework. Network topology describes the physical and logical arrangement of nodes and links on a network, including all hardware (routers, switches, cables), software (apps and operating systems) and transmission media (wired or wireless connections).

Common network topologies include bus, ring, star and mesh.

In a bus network topology, every network node is directly connected to a main cable. In a ring topology, nodes are connected in a loop, so each device has exactly two neighbors. Adjacent pairs are connected directly and nonadjacent pairs are connected indirectly through intermediary nodes. Star network topologies feature a single, central hub through which all nodes are indirectly connected.

Mesh topologies are a bit more complex, defined by overlapping connections between nodes. There are two types of mesh networks—full mesh and partial mesh. In a full mesh topology, every network node connects to every other network node, providing the highest level of network resilience. In a partial mesh topology, only some network nodes connect, typically those that exchange data most frequently.

Full mesh topologies can be expensive and time-consuming to run, which is why they’re often reserved for networks that require high redundancy. Partial mesh, on the other hand, provides less redundancy but is more cost-effective and simpler to run.

Regardless of subtype, mesh networks have self-configuration and self-organization capabilities; they automate the routing process, so the network always finds the fastest, most reliable data path.

Whether it’s the internet protocol (IP) suite, Ethernet, wireless LAN (WLAN) or cellular communication standards, all computer networks follow communication protocols—sets of rules that every node on the network must follow in order to share and receive data. Protocols also rely on gateways to enable incompatible devices to communicate (a Windows computer attempting to access Linux servers, for instance)

Many modern networks run on TCP/IP models, which include four network layers.

• Network access layer. Also called the data link layer or the physical layer, the network access layer of a TCP/IP network includes the network infrastructure (hardware and software components) necessary for interfacing with the network medium. It handles physical data transmission—using Ethernet and protocols such as the address resolution protocol (ARP)—between devices on the same network.

• Internet layer. The internet layer is responsible for logical addressing, routing and packet forwarding. It primarily relies on the IP protocol and the Internet Control Message Protocol (ICMP), which manages addressing and routing of packets across different networks.

• Transport layer. The TCP/IP transport layer enables data transfer between upper and lower layers of the network. Using TCP and UDP protocols, it also provides mechanisms for error checking and flow control.
  
  TCP is a connection-based protocol that is generally slower but more reliable than UDP. UDP is a connectionless protocol that is faster than TCP but does not provide guaranteed transfer. UDP protocols facilitate packet transmission for time-sensitive apps (such as video streaming and gaming platforms) and DNS lookups.

• Application layer. TCP/IP’s application layer uses HTTP, FTP, Post Office Protocol 3 (POP3), SMTP, domain name system (DNS) and SSH protocols to provide network services directly to applications. It also manages all the protocols that support user applications.

Though TCP/IP is more directly applicable to networking, the Open Systems Interconnection (OSI) model—sometimes called the OSI reference model—has also had a substantial impact on computer networking and computer science, writ broadly.

OSI is a conceptual model that divides network communication into seven abstract layers (instead of four), providing a theoretical underpinning that helps engineers and developers understand the intricacies of network communication. The OSI model's primary value lies in its educational utility and its role as a conceptual framework for designing new protocols, making sure that they can interoperate with existing systems and technologies.

However, the TCP/IP model's practical focus and real-world applicability have made it the backbone of modern networking. Its robust, scalable design and horizontal layering approach has driven the explosive growth of the internet, accommodating billions of devices and massive amounts of data traffic.

Using email as an example, let’s walk through an example of how data moves through a network.

If a user wants to send an email, they first write the email and then press the “send” button. When the user presses “send,” an SMTP or POP3 protocol uses the sender’s wifi to direct the message from the sender node and through the network switches, where it’s compressed and broken down into smaller and smaller segments (and ultimately into bits, or strings of 1s and 0s).

Network gateways direct the bit stream to the recipient’s network, converting data and communication protocols as needed. When the bit stream reaches the recipient’s computer, the same protocols direct the email data through the network switches on the receiver’s network. In the process, the network reconstructs the original message until the email arrives, in human-readable form, in the recipient’s inbox (the receiver node).

Computer networks are inescapable, present in many aspects of modern life. In business, relying on computer networks isn’t an option—they are fundamental to the operation of modern enterprises.

Computer networks provide numerous benefits, including:

Networking enables every form of digital communication, including email, messaging, file sharing, video calls and streaming. Networking connects all the servers, interfaces and transmission media that make business communication possible.

Without networking, organizations would have to store data in individual data repositories, which is unsustainable in the age of big data. Computer networks help teams keep centralized data stores that serve the entire network, freeing up valuable storage capacity for other tasks.

Users, network administrators and developers alike stand to benefit from how networking simplifies resource and knowledge sharing. Networked data is easier to request and fetch, so users and clients get faster responses from network devices. And for those on the business side, networked data makes it easier for teams to collaborate and share information as technologies and enterprises evolve.

Not only are well-built networking solutions more resilient, but they also offer businesses more options for cybersecurity and network security. Most network providers offer built-in encryption protocols and access controls (such as multifactor authentication) to protect sensitive data and keep bad actors off the network.