Communication and Networking
Networking
Networking is actually the connection between two or more terminal for the purpose of receive, sent, share data of information.
Networking can be also defined as “group of computers or any electronic devices and associated devices that are connected by different type of communications facilities.”
History
In September 1940 George Stibitz used a teletype machine to send instructions for a problem set from his Model K at Dartmouth College in New Hampshire to his Complex Number Calculator in New York and received results back by the same means. Linking output systems like teletypes to computers was an interest at the Advanced Research Projects Agency (ARPA) when, in 1962, J.C.R. Licklider was hired and developed a working group he called the “Intergalactic Network”, a precursor to the ARPANet.
In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at MIT, a research group supported by General Electric and Bell Labs used a computer (DEC’s PDP-8) to route and manage telephone connections.
Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently conceptualized and developed network systems which used datagrams or packets that could be used in a packet switched network between computer systems.
1965 Thomas Merrill and Lawrence G. Roberts created the first wide area network(WAN).
The first widely used PSTN switch that used true computer control was the Western Electric 1ESS switch, introduced in 1965.
In 1969 the University of California at Los Angeles, SRI (in Stanford), University of California at Santa Barbara, and the University of Utah were connected as the beginning of the ARPANet network using 50 kbit/s circuits. Commercial services using X.25, an alternative architecture to the TCP/IP suite, were deployed in 1972.
Computer networks, and the technologies needed to connect and communicate through and between them, continue to drive computer hardware, software, and peripherals industries. This expansion is mirrored by growth in the numbers and types of users of networks from the researcher to the home user.
Today, computer networks are the core of modern communication. For example, all modern aspects of the Public Switched Telephone Network (PSTN) are computer-controlled, and telephony increasingly runs over the Internet Protocol, although not necessarily the public Internet. The scope of communication has increased significantly in the past decade and this boom in communications would not have been possible without the progressively advancing computer network.
Merits and Demerits of Computer Networks
Merits of Computer Networks
Network is important because by using a network we can—-
CommunicateA network supports communication among users in ways that other media cannot. E-mail, the most popular form of network communication, provides low-cost, printable correspondence with the capability for forwarding, acknowledgment, storage, retrieval, and attachments.
ShareSharing involves not only information (database records, e-mail, graphics, etc.), but also resources (applications, printers, modems, disk space, scanners, etc.) Through its ability to share, a network promotes collaboration. This is the main attraction of p opular software called “groupware” that is designed to allow multiple users to hold electronic meetings and work concurrently on projects.
Play Multiplayer Games: By using LAN or Internet it id possible to play different games by different users from different locations.
Reduced Hardware Cost: Through its ability to share it is possible to use same resources (applications, printers, modems, disk space, scanners, etc.) for multiple numbers of computers. So networking reduces hardware cost.
Centralized Data Management: Centralized data management refers an organization’s electronically stored data. Data warehouses are designed to facilitate reporting and analysis.. However, the means to retrieve and analyze data, to extract, transform and load data, and to manage the data dictionary are also considered essential components of a Centralized data management.
Demerits of Computer Networks
There are some demerits also—-
Security Concerns
Lack of Privacy Information security is important both to companies and consumers that participate in online busin ess. Many consumers are hesitant to purchase items over the Internet because they do not trust that their personal information will remain private. Encryption is the primary method for implementing privacy policies.
Cheating in E-business: Another major security concern that consumers have with e-commerce merchants is whether or not they will receive exactly what they purchase. Online merchants have attempted to address this concern by investing in and building strong consumer brands (Amazon.com, eBay, Overstock.com), and by leveraging merchant/feedback rating systems and e-commerce bonding solutions.
Virus Threats Most personal computers are now connected to the Internet and to local area networks, facilitating the spread of malicious code. Today’s viruses may also take advantage of network services such as the World Wide Web, e-mail, Instant Messaging and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating mal ware.
Others:
Loss of Productivity: Some time people people spent a lot of time in internet or other type of computer network. As a result the productivity of a organization can be lost.
Applications of Networking
E mail Through internet it is possible to send and receive afrom anywhere and anytime. Electronic mail, often abbreviated to e-mail, email, or originally email, is a store-and-forward method of writing, sending, receiving and saving messages over electronic communication systems. The term “e-mail” (as a noun or verb) applies to the Internet e-mail system based on the Simple Mail Transfer Protocol, to network systems based on other protocols and to various mainframe, minicomputer, or internet by a particular systems vendor, or on the same protocols used on public networks.
Web Browsing Users can interact with text, images, videos, music and other information typically located on a Web page at a website on the World Wide Web or a local area network. Text and images on a Web page can contain hyperlinks to other Web pages at the same or different website.
Digital Libraries A digital library is a library in which collections are stored in digital formats (as opposed to print, microform, or other media) and accessible by computers.[1] The digital content may be stored locally, or accessed remotely via computer networks. A digital library is a type of information retrieval system.
Video Conference A videoconference (also known as a video teleconference) is a set of interactive telecommunication technologies which allow two or more locations to interact via two-way video and audio transmissions simultaneously. It has also been called visual collaboration and is a type of groupware. It differs from videophone in that it is designed to serve a conference rather than individuals.
Pager A pager (sometimes called a beeper) is a simple personal telecommunications device for short messages. A one-way numeric pager can only receive a message consisting of a few digits; typically a phone number that the user is then expected to call. Alphanumeric pagers are available, as well as two-way pagers that have the ability to send and receive email, numeric pages, and SMS messages.
E Commerce Electronic commerce, commonly known as e-commerce or eCommerce, consists of the buying and selling of products or services over electronic systems such as the Internet and other computer networks. The amount of trade conducted electronically has grown extraordinarily since the spread of the Internet. A wide variety of commerce is conducted in this way, spurring and drawing on innovations in electronic funds transfer, supply chain management, Internet marketing, online transaction processing, electronic data interchange (EDI), inventory management systems, and automated data collection systems. Modern electronic commerce typically uses the World Wide Web at least at some point in the transaction’s lifecycle, although it can encompass a wider range of technologies such as e-mail as well.
File Transfer A protocol for file transfer or file transfer protocol is a convention or standard that controls or enables the transfer of files between two computing endpoints. Unlike with a general-purpose communication protocol, file transfer protocols are not designed to send arbitrary data or facilitate asynchronous communication such as Telnet sessions. They are meant solely to send the stream of bits stored as a single unit in a file system, plus any relevant metadata such as the filename, file size, and timestamp
Mobile Telephones Mobile phones send and receive radio signals with any number of cell site base stations fitted with microwave antennas. These sites are usually mounted on a tower, pole or building, located throughout populated areas, then connected to a cabled communication network and switching system. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, normally not more than 8 to 13 km (approximately 5 to 8 miles) away.
Cable Televisions Cable television is a system of providing television to consumers via radio frequency signals transmitted to televisions through fixed optical fibers or coaxial cables as opposed to the over-the-air method used in traditional television broadcasting (via radio waves) in which a television antenna is required. FM radio programming, high-speed Internet, telephony and similar non television services may also be provided.
Components of a Network
Server: A server is a computer dedicated to providing one or more services over a computer network, typically through a request-response routine. These services are furnished by specialized server applications, which are computer programs designed to handle multiple concurrent requests. Examples of server applications include mail servers, file servers, web servers, and proxy servers.
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. 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.
Networking Hardware and Software
Networking hardware typically refers to equipment facilitating the use of a computer network. Typically, this includes routers, switches, hubs, gateways, access points, network interface cards, network bridges, modems, ISDN adapters, firewalls and other related hardware.
The most common kind of networking hardware today is copper-based Ethernet adapters, helped largely by its standard inclusion on most modern computer systems. Wireless networking has become increasingly popular, however, especially for portable and handheld devices.
Other hardware prevalent within computer networking is datacenter equipment (such as file servers, database servers and storage areas), network services (such as DNS, DHCP, email etc) as well as other specific network devices such as content delivery.
.Network software is used to efficiently share information among computers. It involves operating system, utilities etc. It encloses the information to be sent in a “package” that contains a “header” and a “trailer”. The header and trailer contain information for the receiving computer, such as the address of that computer and how the information package is coded. Information is transferred between computers as either electrical signals in electric wires, as light signals in fiber-optic cables, or as electromagnetic waves through space.
Resources: Networking resources include applications, printers, modems, disk space, scanners, etc.
Media: Networking media refers the way to connect computers on a network. Network communication media can be dividing into two parts: 1.Physical Media 2.Wireless or Cordless Media
Data Data refers to a collection of organized information, usually the result of experience, observation or experiment, other information within a computer system, or a set of premises. This may consist of numbers, words, or images, particularly as measurements or observations of a set of variables.
Networking Hardware and Software
Router
A specialized network device that determines the next network point to which to forward a data packet toward its destination. Unlike a gateway, it cannot interface different protocols.
Function of Router
Routers are like intersections whereas switches are like streetsIn non-technical terms, a router acts as a junction between two networks to transfer data packets among them. A router is essentially different from a switch that connects devices to form a Local Area Network (LAN). One easy illustration for the different functions of routers and switches is to think of switches as neighborhood streets, and the router as the intersections with the street signs. Each house on the street has an address within a range on the block. In the same way, a switch connects various devices each with their own IP address(es) on a LAN. However, the switch knows nothing about IP addresses except its own management address. Routers connect networks together the way that onramps or major intersections connect streets to both highways and freeways, etc. The street signs at the intersection (routing table) show which way the packets need to flow.
Repeaters
A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation. The term “repeater” originated with telegraphy and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications.
Bridge
A network bridge connects multiple network segments (network domains) along the data link layer. It may be a physical device, such as a network switc h, or it may be a virtual device using bridging. Traffic from one network is forwarded through it to another network. No routing is involved whatsoever. The bridge simply does what its name entails, by connecting two sides from adjacent networks. An example would be an office LAN using a bridge to connect down to an ISP office.
Switch
A device that allocates traffic from one network segment to certain lines {intended destination(s)} which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network.
Ethernet Hub
A connects multiple Ethernet segments together making them act as a single segment. When using a hub, every attached device shares the same broadcast domain and the same collision domain. Therefore, only one computer connected to the hub is able to transmit at a time. Depending on the network topology, the hub provides a basic level 1 OSI (Open Systems Interconnection Reference Model) model connection among the network objects (workstations, servers, etc). It provides bandwidth which is shared among all the objects, compared to switches, which provide a dedicated connection between individual nodes.
Multiplexer
A multiplexer combines more than one input into a single output. In electronics, the multiplexer or mux combines several electrical signals into a single signal. There are different types of multiplexers for analog and digital circuits.
In digital signal processing, the multiplexer takes several separate digital data streams and combines them together into one data stream of a higher data rate. This allows multiple data streams to be carried from one place to another over one physical link, which saves cost.
Network Card
A network card (also called network adapter, network interface card, NIC, etc.) is a piece of computer hardware designed to provide for computer communication over a computer network. Whereas network cards used to be expansion cards to plug into a computer bus, most newer computers have a network interface built into the motherboard, so a separate network card is not required unless multiple interfaces are needed or some other type of network is used.
Firewall
Definition: A network firewall protects a computer network from unauthorized access. Network firewalls may be hardware devices, software programs, or a combination of the two. Network firewalls guard an internal computer network (home, school, business intranet) against malicious access from the outside. Network firewalls may also be configured to limit access to the outside from internal users.
Modem
A modem is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data.
The most familiar example of a modem turns the digital ‘1s and 0s’ of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone System (POTS), and once received on the other side, converts those sounds back into 1s and 0s.
Far more exotic modems are used by internet users every day. In telecommunications, “radio modems” transmit repeating frames of data at very high data rates over microwave radio links. Some microwave modems transmit m ore than a hundred million bits per second.
Optical modems transmit data over optic fibers. Most intercontinental data links now use optic modems transmitting over undersea optical fibers. Optic modems usually use interferometer filters called etalons to separate different colors of light, and then individually turn the pulses of each color of light into electronic digital data streams. Optical modems routinely have data rates in excess of a billion (1×10^9) bits per second. Their bandwidths are currently limited by the thermal expansion of the etalons. Heat changes an etalon’s size and thus its frequency.
Modems can be used over any means of transmitting analog signals, from driven diodes to radio.
These are the most commonly used hardware for network.
Media of Networking
Network communication media can be dividing into two parts:
1. Physical Media
2. Wireless or Cordless Media
1. Physical Media
Coaxial Cable
Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, and usually surrounded by a final insulating layer. This cable is designed to carry a high-frequency or broadband signal, as a high-frequency transmission line. Sometimes DC power (called bias) is added to the signal to supply the equipment at the other end, as in direct broadcast satellite receivers. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields.Coaxial cables may be rigid or flexible. Rigid types have a solid sheath, while flexible types have a braided sheath, both usually of thin copper wire. The inner insulator, also called the dielectric, has a significant effect on the cable’s properties.
Twisted Pair Cable: Twisted pair c abling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In balanced pair operation, the two wires typically carry equal and opposite signals (differential mode) which are combined by addition at the destination. The common-mode noise from the two wires (mostly) cancel each other in this addition because the two wires have similar amounts of EMI that are 180 degrees out of phase. This results in the same effect as subtraction. Differential mode also reduces electromagnetic radiation from the cable, along with the attenuation that it causes.
Optical Fiber: An optical fiber (also spelled fiber) is a transparent thin fiber, usually made of glass or plastic, for transmitting light. Fiber optics is the branch of science and engineering concerned with such optical fibers. Optical fiber is a cylindrical structure that transmits light along its axis. The fiber consists of a core surrounded by a cladding layer. Like other glasses, the glass used in optical fiber has a refractive index of about 1.5. For the fiber to guide the optical signal the refractive index of the core must be slightly higher than that of the cladding, though typically the difference is less than one per cent.
ISDN Line: Integrated Services Digital Network or Isolated Subscriber Digital Network (ISDN), is a telephone system network. Prior to the ISDN, the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to the ISDN defined: Basic Rate Interface (BRI), Primary Rate Interface (PRI) and Broadband-ISDN (B-ISDN). ISDN is a circuit-switched telephone network system that also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires resulting in better voice quality than an analog phone.
2. Wireless or Cordless Media
Microwave System
Microwaves are electromagnetic waves with wavelengths longer than those of infrared light, but shorter than those of radio waves. Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz). However, the boundaries between far infrared light, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
Infrared
Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. The name means “below red” (from the Latin infra, “below”), red being the color of visible light of longest wavelength. Infrared radiation spans three orders of magnitude and has wavelengths between 700 nm and 1 mm.
Satellite System
Satellite System (GNSS) is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. A GNSS allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line of sight by radio from satellites. Receivers on the ground with a fixed position can also be used to calculate the precise time as a reference for scientific experiments
Types of Computer Network
Networks can be categorized in several different ways. One approach defines the type of network according to the geographic area it spans.
According to the geographic area the network spans, the network can be categorized as four types –
Personal Area Network (PAN)
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Local area Network (LAN)
A local area network is a network that spans a relatively small space and provides services to a small number of people. The first LAN was invented by a Law Doctor in 1978. Depending on the number of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: Single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet Cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections. Historically, LANs have featured much higher speeds than WANs. This is not necessarily the case when the WAN technology appears as Metro Ethernet, implemented over optical transmission systems.
Wide area Network (WAN)
A wide area network is a network where a wide variety of resources are deployed across a large domestic area or internationally. An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is a network comprised of many smaller networks. The Internet is considered the largest network in the world.[7]. The PSTN (Public Switched Telephone Network) also is an extremely large network that is converging to use Internet technologies, although not necessarily through the public Internet.
A Wide Area Network involves communication through the use of a wide range of different technologies. These technologies include Point-to-Point WANs such as Point-to-Point Protocol (PPP) and High-Level Data Link Control (HDLC), Frame Relay, ATM (Asynchronous Transfer Mode) and Sonet (Synchronous Optical Network). The difference between the WAN technologies is based on the switching capabilities they perform and the speed at which sending and receiving bits of information (data) occur.
Metropolitan Area Network (MAN)
A metropolitan network is a network that is too large for even the largest of LAN’s but is not on the scale of a WAN. It also integrates two or more LAN networks over a specific geographical area (usually a city) so as to increase the network and the flow of communications. The LAN’s in question would usually be connected via “backbone” lines.
Wireless Networks (WLAN, WWAN)
A wireless network is basically the same as a LAN or a WAN but there are no wires between hosts and servers. The data is transferred over sets of radio transceivers. These types of networks are beneficial when it is too costly or inconvenient to run the necessary cables. For more information, see Wireless LAN and Wireless wide area network. The media access protocols for LANs come from the IEEE.
The most common IEEE 802.11 WLANs cover, depending on antennas, ranges from hundreds of meters to a few kilometers. For larger areas, either communications satellites of various types, cellular radio, or wireless local loop (IEEE 802.16) all have advantages and disadvantages. Depending on the type of mobility needed, the relevant standards may come from the IETF or the ITU.
Network Topology
Topology is the geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line.
This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle, but it would be highly unlikely to find an actual ring topology there.
Network topologies are categorized into the following basic types:
Bus Topology
Ring Topology
Star Topology
Tree Topology
Mesh Topology
Bus Topology
us networks use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium, those devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message. Ethernet bus topologies are relatively easy to install and don’t require much cabling compared to the alternatives. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.
Ring Topology
In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (effectively either “clockwise” or “counterclockwise”). A failure in any cable or device breaks the loop and can take down the entire network..
Star Topology
Many home networks use the star topology. A star network features a central connection point called a “hub” that may be an actual hub or a switch. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.
Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer’s network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)
Tree Topology
Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the “root” of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub ports) alone.
Mesh Topology
Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, like the Internet, employ mesh routing.
More complex networks can be built as hybrids of two or more of the above basic topologies.