On a all of the computers and devices (nodes) on the network connect to a central device

A computer network is a system of computers and computing devices that are connected via communication links. These links allow the computers and other devices to send information over the network.

Network protocols define how information is sent and received. Networks can be defined by their geographic location, the protocols they use, the physical arrangement of the network components and their purpose.

Computer networks can be physical or logical. A physical computer network is a real network comprised of the cable and devices that send data back and forth. Logical networks are software representations of a physical network. They are built on top of a physical network.

Computer networks aim to share information and resources among multiple digital devices. The internet is an example of a computer network. It is made up of many smaller computer networks. Computer networks make things like video streaming, social networks and cloud networks possible.

A network node is a connection point in a communications network. Each node is an endpoint for data transmissions or redistribution. Nodes have either a programmed or engineered capability to recognize, process and forward transmissions to other network nodes.

The concept of network nodes came into being with the use of distributed networks and packet switching. Depending on the application, network nodes perform a variety of functions.

What does a network node do?

A network node sits at a point in the network where it sends, receives, stores or creates information. It transmits data to communicate with other nodes in the network.

In a computer network, nodes can be physical networked devices, such as modems, PCs and printers. These devices recognize transmissions from other nodes and forward them to other nodes. A node checks for identification, such as an IP address, to grant access to the node.

Nodes connect over a link or communication channel. In a computer network these may be cable, fiber optic or wireless connections.

What are the types of network nodes?

There are several ways to categorize nodes. One way is by network type; another is by network topology.

Network type

• Data communications. In data communications, physical network nodes include data communications equipment or devices that sit between data terminal equipment (DTE) and data transmission circuits. These include switches, bridges, modems or hubs that perform signal conversion, coding and line clocking. These nodes also include DTE, such as digital telephone handsets, printers, routers, servers and workstations.
• Internet network. On the internet and with intranets, most physical network nodes are host computers identified by an IP address. However, some data link devices, such as wireless local area network (LAN) access points, do not have IP host addresses. They are considered physical network or LAN nodes rather than internet nodes or hosts.
• LANs and wide area networks. These nodes are devices that perform a specific function. Each one must have a Media Access Control address for each network interface card. Examples include modems with Ethernet interfaces, wireless LAN access points and computers.
• Telecommunications network. In fixed telephone networks, nodes may be public or private telephone exchanges or a computer providing an intelligent network service. In cellular communications, nodes include base station controllers that control one or more base stations. Cellular network base stations are not considered nodes.
• Cable system. In cable systems, nodes use fiber optic cable to connect to businesses and homes served by a common fiber optic receiver within a geographic location. A fiber optic node describes the number of homes or businesses that a specific fiber node can serve.

Network topologies

Another way to categorize nodes is by how they are arranged in a physical computer network. This is known as the network topology approach. Some common network topologies include these four:

1. Bus topology connects individual nodes directly to a main cable.
2. Ring topology has nodes connected in a loop or ring; each node has a neighbor on each side.
3. Star topology connects all nodes to a central hub.
4. Mesh topology has every node connected to every other node.

What are examples and applications of network nodes?

Examples of how network nodes are used include the following:

Print request. An employee sends a print request from a computer to a printer located in another part of the office. The employee's computer is a node on the network. The request travels over the network and through a series of other nodes -- a router, for example -- on the company LAN. The request reaches the printer, also a node; it processes the request and completes the printing job.

Base station controller. This is a node on a cellular network that provides intelligent network services to devices. The base station controller sits between the cell sites and mobile switching center, which are also nodes on the cell network. Base station controllers determine how cell signals should be routed through the network.

Peer-to-peer mesh network. A peer-to-peer mesh network lets mobile devices communicate information without Wi-Fi or cellular service. In a mesh network topology, every node connects to every other node. Cellphones act as nodes and extend their signals to other cellphones in the network that may be experiencing a service outage. IBM's The Weather Company is using this approach to transmit critical information when other networks may be down.

Internet of things. IoT networks connect devices of all types -- not just computers -- to the internet. Each device is a node on the IoT network. Edge nodes create data from IoT devices. Fog nodes add another layer of physical servers that bring real-time analytical processing to IoT networks.

Find out how fog nodes are simplifying edge computing.

A star network is a local area network (LAN) topology in which all nodes -- personal computers (PCs), workstations or other devices -- are directly connected to a common central computer that is often referred to as a hub. Therefore, a star network is often referred to as a hub-and-spoke network topology.

Every workstation connected to the hub is indirectly connected to each workstation using the hub as an intermediary device. Star networks are typically deployed at the access layer of enterprise networks. The access layer uses a centralized network switch to connect all endpoints to the rest of the LAN.

This graphic shows a star network consisting of a central hub. Each workstation is shown as a PC or laptop with the central hub interconnecting all devices. The lines that interconnect endpoint PCs and laptops are the spokes of the star topology. In the real world, a star network can consist of either wired or wireless connections. In this specific case, each spoke is connected to a hub by a wired connection.

How does a star network work?

Because a star network uses a centralized hub, that hub is responsible for controlling communications between devices. However, there are different ways that a central hub can manage these communications. For example, an Ethernet hub is a network device that simply listens to a communication destined for a device on a different spoke and then retransmits -- or broadcasts -- the message out to all spokes. This is the simplest form of a network hub, as it only must repeat the message to all other connected spokes. But this method can become inefficient quickly, as each communication is sent out to all spokes, as opposed to only the spoke the message was intended for.

If too many devices begin communicating on a network hub, the amount of broadcast traffic can quickly reduce network throughput. It also places the Ethernet hub where it physically looks like a star network topology but operates like a traditional bus network topology.

An Ethernet switch, on the other hand, may look like an Ethernet hub from a physical cabling perspective, but it is far more sophisticated when it comes to how the centralized device handles the transmission of communications to the intended spoke device. Ethernet switches eliminate the need to broadcast communications out to all spokes on the star network. Instead, the Ethernet switch maintains a media access control (MAC) address table. This table statically or dynamically maps the physical MAC address to the port or spoke where the spoke endpoint resides. Therefore, if an Ethernet switch knows the MAC address and specific spoke that the MAC address lives on, it can use this information to send a communication directly out to a single spoke, as opposed to broadcasting the communication to all spokes -- unnecessarily using network bandwidth. Ultimately, an Ethernet switch accomplishes the same goal as an Ethernet hub with the added benefit of better network transport efficiency.

Comparing star network topologies with other topologies

The star network topology works well when workstations are deployed randomly throughout a building or facility. With the hub-and-spoke design, it is easy to add or remove workstations, as all cabling is pulled and connected to a central hub.

From a cabling perspective, if the workstations are reasonably close to the vertices of a convex polygon and the system requirements are modest, the ring network topology may serve the intended purpose at a lower cost than the star network topology. If the workstations lie nearly along a straight line, the bus network topology may be best.

In a star network, a cable failure on a single spoke will only affect the spoke endpoint that it links to the central computer. All the other workstations will continue to function normally with the exception that they will not be able to communicate with the device that resides on the failed spoke. In other words, a star network is powerful from this perspective, as a failure on one spoke does not affect communications of other spokes that are in a functioning state. However, the caveat is that, if the central hub were to fail, all spokes on the star network also fail. If any workstation goes down, none of the other workstations will be affected. Therefore, if network redundancy is required, a mesh network topology may be a preferable option.