Node (networking)

In telecommunications networks, a node (Latin nodus, ‘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 active electronic device that is attached to a network, and is capable of creating, receiving, or transmitting information over a communications channel.[1] A passive distribution point such as a distribution frame or patch panel is consequently not a node.

Computer networks

In data communication, a physical network node may either be data communication equipment (DCE) such as a modem, hub, bridge or switch; or data terminal equipment (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 are at least data link layer devices, must have a network address, typically one for each network interface controller it possesses. Examples are computers, packet switches, xDSL modems (with Ethernet interface) and wireless LAN access points. Equipment, such as a hub, repeater or PSTN modem with serial interface, that operate only below the data link layer does not require a network address.

If the network in question is the Internet 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 as 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 or a computer providing some intelligent network service. In cellular communication, switching points and databases such as the Base station controller, Home Location Register, Gateway GPRS Support Node (GGSN) and Serving GPRS Support Node (SGSN) are examples of nodes. Cellular network base stations are not considered to be nodes in this context.

In cable television systems (CATV), this term has assumed a broader context and is generally associated with a fiber optic 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, the nodes are clients, servers or peers. A peer may sometimes serve as client, sometimes server. In a peer-to-peer or overlay network, 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, as it is the case in Amazon's Dynamo.[2]

Cloud computing

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 / 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.[3] There are several means to remedy this problem but all require instilling trust in the end node computer.[4]

See also

References

  1. ^ "Node". Encarta. Microsoft. Archived from the original on 2009-11-01.
  2. ^ "Dynamo: Amazon's Highly Available Key-value Store: 4.2 Partitioning Algorithm" (PDF). http://www.allthingsdistributed.com/: All things distributed. Retrieved 2011-03-17. the basic algorithm is oblivious to the heterogeneity in the performance of nodes. To address these issues, Dynamo uses a variant of consistent hashing: instead of mapping a node to a single point in the circle, each node gets assigned to multiple points in the ring. To this end, Dynamo uses the concept of “virtual nodes”. A virtual node looks like a single node in the system, but each node can be responsible for more than one virtual node. Effectively, when a new node is added to the system, it is assigned multiple positions (henceforth, “tokens”) in the ring.
  3. ^ David D. Clark (April 2009), Architecture from the top down, retrieved 2017-05-14
  4. ^ "LPS-Public".
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 group in group communication systems.A communication endpoint is a discoverable node of communication whose scope may be varied to narrow or broaden the discovery zone. Endpoints facilitate a standard programmable layer of abstraction whereby heterogeneous software systems and/or subsystems may communicate with each other and that the means of communication are decoupled from the communicating subsystems.

Computer terminal

A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying or printing data from, a computer or a computing system. The teletype was an example of an early day hardcopy terminal, and predated the use of a computer screen by decades.The acronym CRT (cathode-ray tube), which once referred to a computer terminal, has come to refer to a type of screen of a personal computer.Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input, but as the technology improved and video displays were introduced, terminals pushed these older forms of interaction from the industry. A related development was timesharing systems, which evolved in parallel and made up for any inefficiencies of the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal.

The function of a terminal is confined to display and input of data; a device with significant local programmable data processing capability may be called a "smart terminal" or fat client. A terminal that depends on the host computer for its processing power is called a "dumb terminal" or a thin client. A personal computer can run terminal emulator software that replicates the function of a terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system.

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). The DTE/DCE classification was introduced by IBM.

V.35 is a high-speed serial interface designed to support both higher data rates and connectivity between DTEs (data-terminal equipment) or DCEs (data-communication equipment) over digital lines.

Two different types of devices are assumed on each end of the interconnecting cable for a case of simply adding DTE to the topology (e.g. to a hub, DCE), which also brings a less trivial case of interconnection of devices of the same type: DTE-DTE or DCE-DCE. Such cases need crossover cables, such as for the Ethernet or null modem for RS-232.A DTE is the functional unit of a data station that serves as a data source or a data sink and provides for the data communication control function to be performed in accordance with the link protocol.

The data terminal equipment may be a single piece of equipment or an interconnected subsystem of multiple pieces of equipment that perform all the required functions necessary to permit users to communicate. A user interacts with the DTE (e.g. through a human-machine interface), or the DTE may be the user.

Usually, the DTE device is the terminal (or a computer emulating a terminal), and the DCE is a modem or another carrier-owned device.

A general rule is that DCE devices provide the clock signal (internal clocking) and the DTE device synchronizes on the provided clock (external clocking). D-sub connectors follow another rule for pin assignment.

25 pin DTE devices transmit on pin 2 and receive on pin 3.

25 pin DCE devices transmit on pin 3 and receive on pin 2.

9 pin DTE devices transmit on pin 3 and receive on pin 2.

9 pin DCE devices transmit on pin 2 and receive on pin 3.This term is also generally used in the Telco and Cisco equipment context to designate a network device, such as terminals, personal computers but also routers and bridges, that's unable or configured not to generate clock signals.

Hence a direct PC to PC Ethernet connection can also be called a DTE to DTE communication. This communication is done via an Ethernet crossover cable as opposed to a PC to DCE (hub, switch, or bridge) communication which is done via an Ethernet straight cable.

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 computers on the periphery of networks/clouds are called end nodes.) End nodes often are not managed to the trusted network‘s high computer security standards. End nodes often have weak/outdated software, weak security tools, excessive permissions, mis-configurations, questionable content and apps, and covert exploitations. Cross contamination and unauthorized release of data from within a computer system becomes the problem.

Within the vast cyber-ecosystem, these end nodes often attach transiently to one or more clouds/networks, some trustworthy and others not. A few examples: a corporate desktop browsing the Internet, a corporate laptop checking company webmail via a coffee shop's open Wi-Fi access point, a personal computer used to telecommute during the day and gaming at night, or app within a smartphone/tablet (or any of the previous use/device combinations). Even if fully updated and tightly locked down, these nodes may ferry malware from one network (e.g. a corrupted webpage or an infected email message) into another, sensitive network. Likewise, the end nodes may exfiltrate sensitive data (e.g. log keystrokes or screen-capture). Assuming the device is fully trustworthy, the end node must provide the means to properly authenticate the user. Other nodes may impersonate trusted computers, thus requiring device authentication. The device and user may be trusted but within an untrustworthy environment (as determined by inboard sensors' feedback). Collectively, these risks are called the end node problem. There are several remedies but all require instilling trust in the end node and conveying that trust to the network/cloud.

End system

In networking jargon, the computers that are connected to a computer network are sometimes referred to as end systems or end stations. They are labeled end systems because they sit at the edge of the network. The end user always interacts with the end systems. End systems are the devices that provide information or services.End systems that are connected to the Internet are also referred to as Internet hosts; this is because they host (run) Internet applications such as a web browser or an email retrieval program. The Internet’s end systems include some computers with which the end user does not interact. These include mail servers and web servers. With the emergence of the Internet of things, household items (such as toasters and refrigerators) as well as portable, handheld computers and digital cameras are all being connected to the Internet as end systems.

End systems are usually connected to each other using switching devices known as routers rather than using single communication link. The path that transmitted information takes from the sending end system, through a series of communications links and routers, to the receiving end system is known as a route or path through the network.

Mirai (malware)

Mirai (Japanese: 未来, lit. 'future') is a malware that turns networked devices running Linux into remotely controlled "bots" that can be used as part of a botnet in large-scale network attacks. It primarily targets online consumer devices such as IP cameras and home routers. The Mirai botnet was first found in August 2016 by MalwareMustDie, a whitehat malware research group, and has been used in some of the largest and most disruptive distributed denial of service (DDoS) attacks, including an attack on 20 September 2016 on computer security journalist Brian Krebs' web site, an attack on French web host OVH, and the October 2016 Dyn cyberattack. According to a chat log between Anna-senpai and Robert Coelho, Mirai was named after the 2011 TV anime series Mirai Nikki.The source code for Mirai was published on Hack Forums as open-source. Since the source code was published, the techniques have been adapted in other malware projects.

Networking hardware

Networking hardware, also known as network equipment or computer networking devices, are physical devices which are required for communication and interaction between devices on a computer network. Specifically, they mediate data in a computer network. Units which are the last receiver or generate data are called hosts or data terminal equipment.

Node

In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex).

SOAP

SOAP (abbreviation for Simple Object Access Protocol) is a messaging protocol specification for exchanging structured information in the implementation of web services in computer networks. Its purpose is to provide extensibility, neutrality and independence. It uses XML Information Set for its message format, and relies on application layer protocols, most often Hypertext Transfer Protocol (HTTP) or Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission.

SOAP allows processes running on disparate operating systems (such as Windows and Linux) to communicate using Extensible Markup Language (XML). Since Web protocols like HTTP are installed and running on all operating systems, SOAP allows clients to invoke web services and receive responses independent of language and platforms.

Secure end node

A Secure End Node is a trusted, individual computer that temporarily becomes part of a trusted, sensitive, well-managed network and later connects to many other (un)trusted networks/clouds. SEN's cannot communicate good or evil data between the various networks (e.g. exfiltrate sensitive information, ingest malware, etc.). SENs often connect through an untrusted medium (e.g. the Internet) and thus require a secure connection and strong authentication (of the device, software, user, environment, etc.). The amount of trust required (and thus operational, physical, personnel, network, and system security applied) is commensurate with the risk of piracy, tampering, and reverse engineering (within a given threat environment). An essential characteristic of SENs is they cannot persist information as they change between networks (or domains).

The remote, private, and secure network might be organization's in-house network or a cloud service. A Secure End Node typically involves authentication of (i.e. establishing trust in) the remote computer's hardware, firmware, software, and/or user. In the future, the device-user's environment (location, activity, other people, etc.) as communicated by means of its (or the network's) trusted sensors (camera, microphone, GPS, radio, etc.) could provide another factor of authentication.

A Secure End Node solves/mitigates end node problem.

The common, but expensive, technique to deploy SENs is for the network owner to issue known, trusted, unchangeable hardware to users. For example, and assuming apriori access, a laptop's TPM chip can authenticate the hardware (likewise a user's smartcard authenticates the user). A different example is the DoD Software Protection Initiative's Cross Fabric Internet Browsing System that provides browser-only, immutable, anti-tamper thin clients to users Internet browsing. Another example is a non-persistent, remote client that boots over the network.A less secure but very low cost approach is to trust any hardware (corporate, government, personal, or public) but restrict user and network access to a known kernel (computing) and higher software. An implementation of this is a Linux Live CD that creates a stateless, non-persistent client, for example Lightweight Portable Security. A similar system could boot a computer from a flashdrive or be an immutable operating system within a smartphone or tablet.

Terminal (telecommunication)

In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters and/or leaves a network. Examples of equipment containing network terminations are telephones, fax machines, computer terminals and network devices, printers and workstations.

History
Pioneers
Transmission
media
Network topology
and switching
Multiplexing
Networks

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.