Communications And The Internet What is Communications? Communication is the process of conveying information from a sender to a receiver with the use of a medium in which the communicated information is understood by both sender and receiver. It is a process that allows organisms to exchange information by several methods. Why do Organizations Communicate? Share information and Data Resources Monitor Activities Process Sales and Orders Share the use of Applications and Processes Communicate with its Staff and Partners Communicate with its Customers Perform Transactions with its Vendors Computers make it possible for organizations to Communicate from point A to B in-house as well as over a wide geography A Medium B This is made possible via a set of Hardware Devices and Communication Software Organizations Communicate using Computers to Various Departments Accounting Sales Production Computers that communicate within an organization form a NETWORK A computer network, also referred to as just a network, consists of two or more computers, and typically other devices as well (such as printers, external hard drives, modems and routers), that are linked together so that they can communicate with each other and thereby exchange commands and share data, hardware and other resources. The devices on a network are referred to as nodes. They are analogous to the knots in nets that have traditionally been used by fishermen and others. Nodes can be connected using any of various types of media, including twisted pair copper wire cable, optical fiber cable, coaxial cable and radio waves. What is a Network Topology? In communication networks, a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines (media). There are two ways of defining network geometry: the physical topology and the logical (or signal) topology. Types of Topologies Ring Bus Star Mesh Tree The Ring Topology In the ring network topology, the workstations are connected in a closed loop configuration. Adjacent (Neighbouring) pairs of workstations are directly connected. Other pairs of workstations are indirectly connected, passing data through one or more intermediate nodes. The Bus Topology In the bus network topology, every workstation is connected to a main cable called the bus. Therefore, in effect, each workstation is directly connected to every other workstation in the network. The Star Topology In the star network topology, there is a central computer or server to which all the workstations are directly connected. Every workstation is indirectly connected to every other through the central computer. The Mesh Topology The mesh network topology employs either of two schemes, called full mesh and partial mesh. In the full mesh topology, each workstation is connected directly to each of the others. In the partial mesh topology, some workstations are connected to all the others, and some are connected only to those other nodes with which they exchange the most data. The Tree Topology The tree network topology uses two or more star networks connected together. The central computers of the star networks are connected to a main bus. Thus, a tree network is a bus network of star networks. N.B. Logical (or signal) topology refers to the nature of the paths the signals follow from node to node. In many instances, the logical topology is the same as the physical topology. But this is not always the case. For example, some networks are physically laid out in a star configuration, but they operate logically as bus or ring networks. Types of Networks TAN – Tiny Area Network LAN – Local Area Network WAN – Wide Area Network MAN – Metropolitan Area Network Tiny Area Network A Connection of four(4) or less Computers Local Area Network A Network that connects computers within the same building or Area such as a Home or small office. Wide Area Network A Network that spans a wide Geography, such as City to City or Country to Country. The Internet is currently the world’s largest Wide Area Network. Metropolitan Area Network A metropolitan area network (MAN) is designed to serve a town or city, and a campus area network is designed to serve a university or other educational institution. Communications Media Data can be communicated from one terminal to the central computer to other terminals through different media. These media are known as data communication channels there are cable, WiFi, microwave, satellite and fiber optics. Cable is the most popular and widely used medium to transmit data from one location to another. Telephone Line Twisted Wire Pair Coaxial Cable Picture of Telephone Line Picture of the Twisted Wire Pair Picture of Coaxial Cable WiFi Wi-Fi (short for "wireless fidelity") is a term for certain types of wireless local area network (WLAN) that use specifications in the 802.11 family. 802.11 is a set of rules That govern the use of these WiFi Frequencies. Wi-Fi has gained acceptance in many businesses, agencies, schools, and homes as an alternative to a wired LAN. Many airports, hotels, and fast-food facilities offer public access to Wi-Fi networks. These locations are known as hot spots. Diagram of a WiFi Configuration Microwaves The term microwave refers to electromagnetic energy having a frequency higher than 1 gigahertz (billions of cycles per second), corresponding to wavelength shorter than 30 centimeters. Microwave signals propagate in straight lines and are affected very little by the troposphere. Satellites In general, a satellite is anything that orbits something else, as, for example, the moon orbits the earth. In a communications context, a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth. There are hundreds of satellites currently in operation. They are used for such diverse purposes as weather forecasting, television broadcast, amateur radio communications, Internet communications, and the Global Positioning System, (GPS). Fiber Optics Fiber optic (or "optical fiber") refers to the medium and the technology associated with the transmission of information as light impulses along a glass or plastic wire or fiber. Fiber optic wire carries much more information than conventional copper wire and is far less subject to electromagnetic interference. Most telephone company long-distance lines are now fiber optic. Picture of Fiber Optic Wires Rules that Govern the Communication of Computers Computers uses network protocols as a means of communicating: A network protocol is a formal set of rules, conventions and data structure that governs how computers and other network devices exchange information over a network. In other words, protocol is a standard procedure and format that two data communication devices must understand, accept and use to be able to talk to each other What is the Internet? The Internet is the worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked Web pages and other documents of the World Wide Web. A little history The Internet started in the 1960s as a way for government researchers to share information. Computers in the '60s were large and immobile and in order to make use of information stored in any one computer, one had to either travel to the site of the computer or have magnetic computer tapes sent through the conventional postal system. Another catalyst in the formation of the Internet was the heating up of the Cold War. The Soviet Union's launch of the Sputnik satellite spurred the U.S. Defense Department to consider ways information could still be disseminated even after a nuclear attack. This eventually led to the formation of the ARPANET (Advanced Research Projects Agency Network), the network that ultimately evolved into what we now know as the Internet. ARPANET was a great success but membership was limited to certain academic and research organizations who had contracts with the Defense Department. In response to this, other networks were created to provide information sharing. The Internet Today The Internet today is a large-scale network of millions of computers that allows continuous communication across the globe. The various applications of the Internet are: •The World-Wide Web (the web or WWW) •Electronic Mail (E-Mail) •File Transfer Protocol (FTP) •Internet Relay chat (IRC) •USENET (a news service) The World Wide Web The www is the reason the Internet has become as popular as it has. This is the part of the Internet that the majority of users see — the websites and the pages that make them up. The web is the most widely used service of the Internet, accessed through a web browser like Internet Explorer or Mozilla Firefox. These pieces of software are gradually integrating other parts of the Internet into them (most notably email and ftp), so that eventually we will have one interface to the entire array of services the Internet offers. Electronic Mail (E-Mail) Electronic Mail works in much the same way as traditional mail (now charmingly labeled 'snail-mail') does. Anyone is allowed to sign up for an email address and then people can send you messages, or attach files from their computer and send them too. The main benefit of email is the close to instantaneous delivery of messages that occurs. You can send an email to the other side of the world and it will arrive in less than a minute. You can also sign up to weekly newsletters and have information you want delivered right to your computer. E.g. Of an email address is : [email protected] N.B.