Node (networking)

In the world of networking, a node is a vital point of connection. A node can be a redistribution point where data is sent to new paths. It can also be a communication endpoint where information stops. Nodes are the building blocks of telecommunication and computer networks. They allow information to flow through a communication channel. Without these points, a network would have no way to direct or receive data.

Physical network nodes are electronic devices attached to a network. These devices can create, receive, or transmit information. We can divide these physical nodes into two main categories. The first category is data communication equipment, or DCE. This includes tools like a modem, a hub, a bridge, or a switch. The second category is data terminal equipment, or DTE. These are devices that use the data, such as a digital telephone handset, a printer, or a host computer. Note that a passive distribution point, like a patch panel, is not considered a node.

In computer networks, nodes function based on different layers of communication. For a local area network (LAN) or a wide area network (WAN), specific rules apply. Every node participating on the data link layer must have a network address. This is usually one address for each network interface controller the device has. Examples of these nodes include computers and wireless access points. Some equipment, like an Ethernet hub, operates below the data link layer. Because of this, it does not require a network address.

When we look at the Internet or an intranet, the term "Internet node" is used. Many physical network nodes in these systems are host computers. These hosts are identified by a unique IP address. While all hosts are physical network nodes, not all physical nodes are hosts. For instance, some switches and bridges do not have an IP host address. These devices are considered LAN nodes or physical network nodes, but not Internet nodes. This distinction depends on whether the device has a specific host identity on the larger network.

Different industries use the term "node" in unique ways. In fixed telephone networks, a node might be a private or public telephone exchange. It could also be a remote concentrator or a computer providing intelligent network services. Cellular communication uses different types of nodes. These include the base station controller and the home location register. Other examples are the gateway GPRS support node (GGSN) and the serving GPRS support node (SGSN). Interestingly, cellular base stations are not considered nodes in this specific context.

In cable television (CATV) systems, the term has a much broader meaning. It is often associated with a fiber optic node. This node serves a specific geographic area. It connects a group of homes or businesses to a common fiber optic receiver. Engineers often describe these nodes by the number of homes passed by the specific fiber node. In distributed systems, nodes take on roles like clients, servers, or peers. In a peer-to-peer network, some nodes are called supernodes. These supernodes actively route data for themselves and other devices.

Finally, we must consider the edge of the network, known as the periphery. Individual computers on this edge are called end nodes. These devices often connect to clouds only for a short time. In cloud computing, a user's computer is a common end node. Because the cloud host does not manage these computers, they can present risks. This challenge is known as the end node problem. To solve this, the system must find ways to instill trust in the end node computer.