Common network terms

Node

In communication networks, a node (Latin nodus, ‘knot’) is a connection point, either a redistribution point or a communication endpoint (some terminal equipment). The definition of a node depends on the network and protocol layer referred to. A physical network node is anactive electronic device that is attached to a network, and is capable of sending, receiving, or forwarding information over a communications channel.A passive distribution point such as a distribution frame is consequently not a node.In network theory or graph theory, the term node refers to a point in a network topology at which lines intersect or branchIn data communication, a physical network node may either be a data circuit-terminating equipment (DCE) such as a modem, hub, bridge or switch; or a data terminal equipment (DTE) such as a digital telephone handset, a printer or a host computer, for example a router, a workstation or a server.If the network in question is a LAN or WAN, every LAN or WAN node (that are at least data link layer devices) must have a MAC address. Examples are computers, packet switches and ADSL modem (with Ethernet interface). Note that a hub constitutes a physical network node, but not a LAN node in this sense, since a hubbed network logically is a bus network. Analogusly, a repeater or PSTN modem (with serial interface) are physical network nodes but not LAN nodes in this sense.If the network in question is the Internet, 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, datalink layer devices such as switches, bridges and WLAN access points do not have an IP host address (except sometimes for administrative purposes), and are not considered as Internet nodes, but as physical network nodes or LAN nodes.If the network in question is a distributed system, the nodes are clients, servers or peers. In a peer-to-peer or overlay network, nodes that actively route data for the other networked devices as well as themselves are called supernodesIn 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 as 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.

Client

A client is an application or system that accesses a remote service on another computer system, known as a server, by way of a network.^[1] The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer.The client-server model is still used today on the Internet, where a user may connect to a service operating on a remote system through the Internet protocol suite. Web browsers are clients that connect to web servers and retrieve web pages for display. Most people use e-mail clients to retrieve their e-mail from their internet service provider's mail storage servers. Online chat uses a variety of clients, which vary depending on the chat protocol being used. Game Clients usually refer to the software that is the game in only multiplayer online games for the computer. Increasingly, existing large client applications are being switched to websites, making the browser a sort of universal client. This avoids the hassle of downloading a large piece of software onto any computer you want to use the application on. An example of this is the rise of webmail.In personal computers and computer workstations, the difference between client and server operating system is often just a matter of marketing - the server version may contain more operating system components, allow more simultaneous logins, and may be more expensive, while the client version may contain more end-user software. There are three types as in thin,fat and hybrid.

Server

In information technology, a server is a computer program that provides services to other computer programs (and their users) in the same or other computers.The computer that a server program runs in is also frequently referred to as a server (though it may be used for other purposes as well).In the client/server programming model, a server is a program that awaits and fulfills requests from client programs in the same or other computers. A given application in a computer may function as a client with requests for services from other programs and also as a server of requests from other programs.Specific to the Web, a Web server is the computer program (housed in a computer) that serves requested HTML pages or files. A Web client is the requesting program associated with the user. The Web browser in your computer is a client that requests HTML files from Web serversAny computer or device serving out applications or services can technically be called a server. In an office or enterprise environment, the network server is easy to identify. A DSL/Cable modem router qualifies as a server because it provides a computer with application services like IP address assignment (via DHCP), NAT, and a firewall that helps protect a computer from external threats. iTunes software implements a music server to stream music between computers. Many home users create shared folders and printers. Another example are the many servers that are used for hosting online games such as Everquest, World of Warcraft, Counter-Strike and Eve Online.

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Input and output

Magnetic ink character-recognition


In computing, a technique that enables special characters printed in magnetic ink to be read and input rapidly to a computer. MICR is used extensively in banking because magnetic-ink characters can be machine-read with much greater accuracy than human reading or other optical character recognition (OCR) systems, and are therefore ideal for marking and identifying the account and sort code numbers on cheques.MICR encodes two very important numbers on the bottom of a check: the American Banker's Association (ABA) routing number and an account number. The ABA routing number, sometimes called an ABA number or just a routing number, uses a combination of codes to indicate the institution where the check was issued. The code, which always totals nine digits, expresses a unique identifier composed of a four-digit Federal Reserve routing symbol, a four-digit ABA institution number and a single check digit. The second set of numbers printed on the bottom of the check represents the bank account number of the associated checking account.


Optical-character recognition


optical character recognition refers to the branch of computer science that involves reading text from paper and translating the images into a form that the computer can manipulate (for example, into ASCII codes).An OCR system enables you to take a book or a magazine article, feed it directly into an electronic computer file, and then edit the file using a word processor.
All OCR systems include an optical scanner for reading text, and sophisticated software for analyzing images. Most OCR systems use a combination of hardware (specialized circuit boards) and software to recognize character, although some inexpensive systems do it entirely through software. Advanced OCR systems can read text in large variety of fonts, but they still have difficulty with handwritten text.
The potential of OCR systems is enormous because they enable users to harness the power of computers to access printed documents. OCR is already being used widely in the legal profession, where searches that once required hours or days can now be accomplished in a few seconds.


Dot matrix printer

A dot matrix printer or impact matrix printer is a type of computer print with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter or daisy whell printers, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. Because the printing involves mechanical pressure, these printers can create carbon copies and carbonless copies.Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which is driven forward by the power of a tiny electromagnet or solenoid, either directly or through small levers (pawls). Facing the ribbon and the paper is a small guide plate (often made of an artificial jewel such as sapphire or ruby) pierced with holes to serve as guides for the pins. The moving portion of the printer is called the print head, and when running the printer as a generic text device generally prints one line of text at a time. Most dot matrix printers have a single vertical line of dot-making equipment on their print heads; others have a few interleaved rows in order to improve dot density.These machines can be highly durable. When they do wear out, it is generally due to ink invading the guide plate of the print head, causing grit to adhere to it; this grit slowly causes the channels in the guide plate to wear from circles into ovals or slots, providing less and less accurate guidance to the printing wires. Eventually, even with tungsten blocks and titanium pawls, the printing becomes too unclear to read.Although nearly all inkjet,thermal, and laser printers print closely-spaced dots rather than continuous lines or characters, it is not customary to call them dot matrix printers.

Platters

One of the disks in a hard disk drive. Each platter provides a top and bottom recording surface. There may be only one or several platters in a drive with each platter having its own pair of read/write heads. When the computers is turned in,these platters will begun to rotate at so many rotations per minute(RPM)This rate varies depending upon the model of hard drive you have; an example of how fast a hard drive may spin is 7200 RPM. As the disk platters are rotating, the read/write head accesses information on one of the platters. To help store and retrieve the data from the platter, data is stored in tracks,sectors and cylinder on each platter.Above is a graphic example of what the inside of a hard disk drive looks like and examples of a hard disk drive platter. As can be seen in the desktop computer hard disk drive this drive has three different platters.

Photo printers


A photo printer is a printer(usually an inkjet printer) that is specifically designed to print high quality digital photos on photo paper. These printers usually have a very high number of nozzles and are capable of printing droplets as small as 1 picoliter.Wireless photo printers use WiFi signals to communicate with your wireless home network. This lets you print to them from any computer connected to the network.It also let you roam around your house with a laptop and still be able to print your photos.Some cameras can communicate to wireless printers directly, so that you don’t need to load the pictures on your computer before you can print them.


Portable printer

Why do you need a portable printer?
If you want to print a variety of documents, your main choices are the all-purpose Hewlett-Packard Deskjet 450 models ($250 to $350) and the Canon Pixma IP90($249). Both print color graphics and text on standard 8.5-by-11-inch paper or images on photo paper.
If you just need to print snapshots, consider a portable photo printer such as HP's Photosmart models ($150 to $200). The Photosmart models are nicely compact, but they don't print anything but 4-by-6 snapshots.
Read "Print Anything, Anywhere You Go," for an overview of what's available.When you take a portable printer on a business trip, you can conveniently print such things as:
Photos of products or real-estate properties to give clients
Web pages to share with colleagues in meetings
PowerPoint presentations for backup purposes (this is particularly important if you revise your presentation on the road)
Driving directions from an online mapping site
Airplane boarding passes
Contracts
Among portable printers, there are differences to consider in functionality, price, size and weight, quality and speed, and accessories.


Multifunctional devices

An MFP (Multi Function Product/ Printer/ Peripheral), multifunctional, all-in-one (AIO), or Multifunction Device (MFD), is an office machine which incorporates the functionality of multiple devices in one, so as to have a smaller footprint in a home or small business setting (the SOHO market segment), or to provide centralized document management/distribution/production in a large-office setting. A typical MFP may act as a combination of some or all of the following devices:
1.Printer
2.Scanner
3.Photocopier
4.Fax
5.E-mail
Many MFP types, regardless of the category they fall in to, also come in a "printer only" variety, which is the same model without the scanner unit included. This is even the case with devices where the scanner unit physically appears to be highly integrated in to the product.


Fax machine


a device that can send or receive pictures and text over a telephone line. Fax machines work by digitizing an image -- dividing it into a grid of dots. Each dot is either on or off, depending on whether it is black or white. Electronically, each dot is represented by a bit that has a value of either 0 (off) or 1 (on). In this way, the fax machine translates a picture into a series of zeros and ones (called a bit map) that can be transmitted like normal computer data. On the receiving side, a fax machine reads the incoming data, translates the zeros and ones back into dots, and reprints the picture.A fax machine consists of an optical scanner for digitizing images on paper, a printer for printing incoming fax messages, and a telephone for making the connection. The optical scanner generally does not offer the same quality of resolution as stand-alone scanners. Some printers on fax machines are thermal, which means they require a special kind of paper.


Internet telephony


A category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls. For users who have free, or fixed-price Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. To date, however, Internet telephony does not offer the same quality of telephone service as direct telephone connections.
There are many Internet telephony applications available. Some, like CoolTalk and NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products. In order to use a wireless internet phone, you would need to have a broadband wireless system set up in your home or office. To do this, you would have one computer into which the broadband signal was sent. You would then set up a wireless router, which allowed the signal to be sent from the base computer to other computers in your home. Next, you’ll want to set up the phone system that you’ll be using. You can use a regular telephone, but if you want to go completely wireless there are companies that use a telephone keypad that is displayed right on your computer screen.
You’ll then need to subscribe to an Internet phone provider. There are some companies, such as Vonage, which allow you to make calls to mobile phones and regular landlines. You can also find services that just allow calls from computer to computer.

Telephony


Telephones were originally connected directly together in pairs. Each user had separate telephones wired to the various places he might wish to reach. This became inconvenient when people wanted to talk to many other telephones, so the telephone exchange was invented. Each telephone could then be connected to other local ones, thus inventing the local loop and the telephone call. Soon, nearby exchanges were connected by trunk lines, and eventually distant ones were as well.Digital telephony is the use of digital technology in the provision of telephone services and systems. Almost all telephone calls are provided this way, but sometimes the term is restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone. Telephony was digitized to cut the cost and improve the quality of voice services, but digital telephony was then found useful for new network services (ISDN) to transfer data speedily over telephone lines.
IP telephony is a modern form of telephony which uses the TCP/IP protocol popularized by the Internet to transmit digitized voice data. Contrast this with the operation of POTS (an acronym for "plain old telephone service").
Computer telephony integration (CTI) enables computers to know about ad control phone functions such as making and receiving voice, fax, and data calls with telephone directory services and caller identification. The integration of telephone software and computer systems is a major development in the evolution of the automated office.