telecommunications network A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, mes ...

s, a node (, ‘knot’) is either a redistribution point or a

communication endpoint A communication endpoint is a type of communication network node. It is an interface exposed by a communicating party or by a communication channel. An example of the latter type of a communication endpoint is a publish-subscribe topic or a grou ...

. The definition of a node depends on the network and protocol layer referred to. A physical network node is an electronic device that is attached to a network, and is capable of creating, receiving, or transmitting information over a

communication channel A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for informa ...

. A

passive Passive may refer to: * Passive voice, a grammatical voice common in many languages, see also Pseudopassive * Passive language, a language from which an interpreter works * Passivity (behavior), the condition of submitting to the influence of o ...

distribution point such as a

distribution frame Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

patch panel A patch panel is a device or unit featuring a number of jacks, usually of the same or similar type, for the use of connecting and routing circuits for monitoring, interconnecting, and testing circuits in a convenient, flexible manner. Patch ...

is consequently not a node.

Computer networks

In data communication, a physical network node may either be

data communication equipment A data circuit-terminating equipment (DCE) is a device that sits between the data terminal equipment (DTE) and a data transmission circuit. It is also called data communication(s) equipment and data carrier equipment. Usually, the DTE device i ...

(DCE) such as a

modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more c ...

, hub,

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...

switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...

; or

data terminal equipment Data terminal equipment (DTE) is an end instrument that converts user information into signals or reconverts received signals. These can also be called tail circuits. A DTE device communicates with the data circuit-terminating equipment (DCE) ...

(DTE) such as a digital telephone handset, a printer or a

host computer A network host is a computer or other device connected to a computer network. A host may work as a server offering information resources, services, and applications to users or other hosts on the network. Hosts are assigned at least one network ...

. If the network in question is a

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a large ...

(LAN) or

wide area network A wide area network (WAN) is a telecommunications network that extends over a large geographic area. Wide area networks are often established with leased telecommunication circuits. Businesses, as well as schools and government entities, u ...

(WAN), every LAN or WAN node that participates on the

data link layer The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between nodes on a network segment across the physical layer. The data link layer p ...

must have a

network address A network address is an identifier for a node or host on a telecommunications network. Network addresses are designed to be unique identifiers across the network, although some networks allow for local, private addresses, or locally admini ...

, typically one for each

network interface controller A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network. Ear ...

it possesses. Examples are computers, a DSL modem with Ethernet interface and

wireless access point In computer networking, a wireless access point (WAP), or more generally just access point (AP), is a networking hardware device that allows other Wi-Fi devices to connect to a wired network. As a standalone device, the AP may have a wired ...

. Equipment, such as an

Ethernet hub An Ethernet hub, active hub, network hub, repeater hub, multiport repeater, or simply hub is a network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/out ...

or modem with

serial interface In computing, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in paralle ...

, that operates only below the data link layer does not require a network address. If the network in question is the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...

or an

intranet An intranet is a computer network for sharing information, easier communication, collaboration tools, operational systems, and other computing services within an organization, usually to the exclusion of access by outsiders. The term is used in c ...

, many physical network nodes are host computers, also known as ''Internet nodes'', identified by an

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

, and all hosts are physical network nodes. However, some data-link-layer devices such as switches, bridges and wireless access points do not have an IP host address (except sometimes for administrative purposes), and are not considered to be Internet nodes or hosts, but are considered physical network nodes and LAN nodes.

Telecommunications

In the fixed telephone network, a node may be a public or private

telephone exchange telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

, a

remote concentrator In modern telephony a remote concentrator, remote concentrator unit (RCU), or remote line concentrator (RLC) is a concentrator at the lowest level in the telephone switch hierarchy. Subscribers' analogue telephone/PSTN lines are terminated on co ...

or a computer providing some intelligent network service. In cellular communication, switching points and databases such as the

base station controller The base station subsystem (BSS) is the section of a traditional cellular telephone network which is responsible for handling traffic and signaling between a mobile phone and the network switching subsystem. The BSS carries out transcoding of s ...

home location register Network switching subsystem (NSS) (or GSM core network) is the component of a GSM system that carries out call out and mobility management functions for mobile phones roaming on the network of base stations. It is owned and deployed by mobi ...

, gateway GPRS Support Node (GGSN) and serving GPRS support node (SGSN) are examples of nodes. Cellular network

base station Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service." The term is used in the context of mobile telephony, wireless c ...

s are not considered to be nodes in this context. In

cable television Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with bro ...

systems (CATV), this term has assumed a broader context and is generally associated with a

fiber optic An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means t ...

node. This can be defined as those homes or businesses within a specific geographic area that are served from a common fiber optic receiver. A fiber optic node is generally described in terms of the number of "homes passed" that are served by that specific fiber node.

Distributed systems

If the network in question is a

distributed system A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sci ...

, the nodes are clients, servers or peers. A peer may sometimes serve as client, sometimes server. In a

peer-to-peer Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network. They are said to form a peer-to-peer ...

overlay network An overlay network is a computer network that is layered on top of another network. Structure Nodes in the overlay network can be thought of as being connected by virtual or logical links, each of which corresponds to a path, perhaps through ...

, nodes that actively route data for the other networked devices as well as themselves are called supernodes. Distributed systems may sometimes use ''virtual nodes'' so that the system is not oblivious to the heterogeneity of the nodes. This issue is addressed with special algorithms, like

consistent hashing In computer science, consistent hashing is a special kind of hashing technique such that when a hash table is resized, only n/m keys need to be remapped on average where n is the number of keys and m is the number of slots. In contrast, in most tr ...

, as it is the case in Amazon's Dynamo. Within a vast computer network, the individual computers on the periphery of the network, those that do not also connect other networks, and those that often connect transiently to one or more

clouds In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid drop (liquid), droplets, ice crystals, frozen crystals, or other particulates, particles suspended in the atmosphere of a planetary body or similar space. ...

are called end nodes. Typically, within the cloud computing construct, the individual user or customer computer that connects into one well-managed cloud is called an end node. Since these computers are a part of the network yet unmanaged by the cloud's host, they present significant risks to the entire cloud. This is called the

end node problem The end node problem arises when individual computers are used for sensitive work and/or temporarily become part of a trusted, well-managed network/cloud and then are used for more risky activities and/or join untrusted networks. (Individual comp ...

. There are several means to remedy this problem but all require instilling trust in the end node computer.

References

{{DEFAULTSORT:Node (Networking) Computer networking Routing

Computer networks

Telecommunications

Distributed systems

See also

References