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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. 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 ...
or
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, 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 somethi ...
or
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. If the network in question is a local area network (LAN) or wide area network (WAN), every LAN or WAN node that participates on the data link layer must have a network address, 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. 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, 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, pub ...
or an intranet, many physical network nodes are host computers, also known as ''Internet nodes'', identified by an IP address, 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, 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 The GPRS core network is the central part of the general packet radio service (GPRS) which allows 2G, 3G and WCDMA mobile networks to transmit IP packets to external networks such as the Internet. The GPRS system is an integrated part of the G ...
(SGSN) are examples of nodes. Cellular network base stations 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 or
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 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. There are several means to remedy this problem but all require instilling trust in the end node computer.


See also

* End system *
Middlebox A middlebox is a computer networking device that transforms, inspects, filters, and manipulates traffic for purposes other than packet forwarding. Examples of middleboxes include firewalls, network address translators (NATs), load balancers, and ...
*
Networking hardware Networking hardware, also known as network equipment or computer networking devices, are electronic devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data transmission in ...
* Terminal (telecommunication)


References

{{DEFAULTSORT:Node (Networking) Computer networking Routing