CIS Chapter 6
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Date Created: 09/28/16
Chapter 6. What is a computer network? A computer network is a system that connects computer and other devices (printers) via communications media, so that data and info can be transmitted among them. Bandwidth- the transmission capacity of a network (bit/sec) Broadband- the transmission capacity of a communication medium faster than 25Mbps for downloading and 4 Mbps for upload. Ex. DSL, cable Local area network LAN- connects two or more devices in a limited geographical region, usually within the same building, so every device can communicate with every other device. Every device in the LAN has a network interface card (NIC) – allows the device to physically connect to the LAN’s communication medium. Many LANs have a file server or network server, which contains various software and data for the network. Wild area of networks WAN- a network that covers a large geographical area connect multiple LANs, provided by telephone companies. Ex. AT&T, Internet Router- a communications processor that routes messages from a LAN to the internet, across several LANs, or across a wide area network. Enterprise Networks Enterprise network- connection of all LANs and WANs in organizations. Backbone networks – high-speed central networks to which multiple smaller networks connect. LANs connected to the backbone WAN – embedded LANs. Software- defined networks (SDN) – an emerging technology that is becoming increasingly important to help organizations manage their data flows across their enterprise networks. Corporate backbone network- high-speed central networks to which multiple smaller networks connect. Network fundamentals Computer network communicate via digital signals, discrete pulses that are representing a series of bits (0 and 1), allow to convey information in a binary form. Public telephone system was originally designed to carry voice signals or sounds in an analog wave format. Information should be converted by a dial- up modem. Cable modems – modems that operate over coaxial cable (cable TV), it offers broadband access to the internet or corporate intranets. DSL modems operate on the same lines as voice telephones and dial-up modems. It always maintains connection. Communications media and channels. Communication channel – a pathway to connect data from one location to another. Composed of: cable (twisted- pair, wire, coaxial cable) and broadcast (microwave, radio). Wireline or cable media use physical wires or cables to transmit data and information. The alternative- broadcast media or wireless media- data transmissions over electronic media. Twisted-pair wire-the most prevalent form of communication wiring and is used for almost all business telephone wiring. (Strands of copper wire twisted in pair) + inexpensive - Slow +widely available - Subject to interference +easy to work with - Can be easily tapped by unintended receivers Coaxial cable- consist of insulated copper wire. + less susceptible - More expensive + carry more data - Difficult to work with +high-speed data traffic - Inflexible Fiber optics- consists of thousands of very thin filaments of glass fibers that transit info via light pulses generated by lasers: + Smaller and lighter + transmit more data + Greater security. Network Protocol Nodes- devices that are connected to the network to transmit and receive data. Protocol- a common sets of rules and procedures to work of nodes together, that enable them to communicate. Ethernet – a common LAN protocol. Transmission control protocol/ internet protocol (TCP/IP) - is the protocol of the internet uses a suite of protocols. The TCP protocol: - Manages the movement of data packets between computers; - Sequences the transfer of packets; - Acknowledges the packets that have been transmitted. IP (Internet protocol) - responsible for dissembling, delivering, and reassembling the data during transmission. Packets – small, fixed bundles of data. Packet switching – transmission technology that breaks up blocks of text into packets. Packet-switching network are reliable and fault tolerant, can be rerouted around the path if network is busy. TCP/IP functions in: 1) Application layer – enable clients application programs to access the other layers (HTTP) 2) Transport layer- provides the application layer with communication and packet services. (TCP) 3) Internet layer- responsible for addressing, routing and packaging data packets. (IP) 4) Interface layer- places packets on, and receives them from the network medium. TCP/IP is very popular with business organization because of its reliability and the ease with which is can support intranets and related functions. Types of network processing. Distributed processing divides processing work among two or more computers, enables computer in different locations to communicate. Client/ Server computing- links two or more computers in an arrangement in which some machines, called servers provide computing services for PCs user, clients. It leads to the idea of “Fat clients” – have large storage and processing power, can rein local programs. “Thin clients” – have no local storage and only limited processing power. Peer- to-peer processing(p2p processing)- type of clients/server distributed processing where each computer acts as both a client and a server. 1) Unused CDU power among network computers SETI@home- from open-source project, can be downloaded at no cost. 2) Real-time , Person-to-person Share points workspace- use buddy lists to establish a common and allow real-time collaboration. 3) Advanced search and file sharing- searches of millions of peer system. Used to discover other users. The internet and the World Wide Web. The internet (the net) – is a global WAN that connects approximately 1 million org. computer networks in more than 200 countries. Internet backbone- the primary network connections and telecommunications lines that link the nodes. Intranet- a network that uses internet protocol so that users can take advantage of familiar applications and work habits. In contrast, extranet- connects parts of the intranets of different organizations, enables to communicate securely with virtual private networks. (VPNs) Leading internet firms: - Qihoo 360- online security software; - JD.com – online retailer; - Jiayan.com- china’s dating site; - Netease – major news portal for China; - 58.com- China’s version of Craigslast. Accessing the internet Connection via an online service Internet service provider (ISP) - company that provides Internet connection for a free. Ex. Comcast, AT&T, Verizon. ISPs connect through network access points (NAPs), exchange points for Internet traffic, which determine how traffic is routed. Connecting via other means Internet kiosk, Accessing from smartphones and tables; fiber-to-the- home (FTTH) - connecting fiber-optic cable directly t homes. Address on the internet Internet protocol (IP) address- assigned address of each computer that distinguishes it from all other companies. Consists of sets of numbers, in four parts, separated by dots. IP addressing schemes: 1) IPv4 – most widely used, consists of 32 bits, 2 32 possibilities for IP addresses. 2) IPv6 consists of 128 bits, 2128 possibilities for distinct IP addresses. The Internet Corporation for assigned names (ICANN) - coordinates these unique addresses. Each computer also has a name which are derived form a system: domain name system (DNS). Domain names- consists of multiple parts, separated by dots, read from right to left. Business.auburn.edu- the rightmost part is its top-level domain (TLD). TDL- the domain at the highest level in the hierarchical Domain Name System. Internet Assigned Numbers Authority (IANA) in charge of maintaining the DNS root zone. Distinguishes: - Country-code top-level domains (ccTLD) –establishes for country. Ex. .it –Italy, ru – Russia. - International country code top-level domains (IDNccTLD) – in non-Latin character Ex. Arabic or Chinese. - Generic top-level domains (gTLD) Ex. Gov, com, coop,pro. The future of the internet Internet 2 develops and deploys advance education, online simulation, and virtual laboratories. The World Wide Web WWW – system of universally accepted standards for storing, retrieving, formatting, and displaying information via a client/ server architecture. Hypertext- the underlying concept defining the structure of the www. Hyperlink- references to other text that the reader can immediately access. It’s connecting from a hypertext file to another location or file. Web site- all the pages of a particular company or individual. Uniform resource locator (URL) – points to the address of a specific resource on the Web. Network Applications: Discovery Search engine - a computer program that searches for specific information by the keywords and then reports the results. WebCrawler- computer programs that browse the web and create a copy of all visited pages. Ex.: Google, Bing, Yahoo! Metasearch engines- search several engines at once and then the findings to answer user’s queries. Ex.: Metacrawler, Surfwax. Portals- a web- based, personalized gateway to information knowledge that provides relevant information from different IT systems. A commercial (public) portal- intended for broad and diverse audiences, and it offers routine content, some of t in real time (stock ticket) most popular type Ex.: Lycos, Microsoft Network An affinity portals offers a single points of entry to an entire community of affiliated interests (hobby group, political party). A corporate portal- offers a personalized, single points of access through a Web browser to critical business information located inside and outside of organizations. (Known as enterprise, information or enterprise information portals) Industry- wide portals, serves entire industries. Ex.: TruckNet Network Applications: Discovery Communication technologies – e-mail, call centers, chat rooms and voice. Electronic mail (e-mail) – largest –volume app running over the internet. Web-based call centers (customer care centers) - web-based customer support. Ex.: contact software vendor for tech-support Electronic chat rooms – an arrangement whereby participants exchange conversational messages in real time in a chat room: - Web-based- allow to send messages using a Web browser and visiting a Web chat site. - E-mail based- internet relay chat (IRC) - provide online experts for answer questions. Voice communication. Voice-over-internet protocol (VoIP) - your analog voice signals digitized, sectioned into packets, and sent over Internet. Ex.: skype, Vonage Unified communication (UC) – simplifies and integrates all forms of communications on common hardware and software platform. Presence services- enable users to know where their intended recipients are and if they are available, in real time. Telecommunicating- knowledge workers (“digital nomads”) - group of highly prized workers, able to work anywhere and anytime, have no permanent office at their companies. Network Applications: Collaboration Collaboration refers to effort by two or more entities who work together to accomplish certain tasks. Workgroup- two or more individuals who works to perform the task. Workflow- the movement of information that make up an organization’s work procedures. Virtual collaboration – the use of digital technologies that enable organization or individuals who are geographically dispersed to collaboratively plan, design, work. Synchronous – team members meet at the same time. Asynchronously – team members can’t meet together at the same time. Crowdsourcing – type I which an organization outsources a task to an undefined, generally large group in the form of an open call. Teleconferencing – the use of electronic communication technologies that enables two or more people at different locations to hold a conference. Videoconferencing- participants in one location can view participants, documents at other locations (telepresence). Network Applications: Educational E-learning- learning supported by the Web. Distance learning (DL) refers to any learning situation in which teachers and students don’t meet face-to-face. Massive Open Online sources (MOOCs) tool for democratizing higher education. Virtual Universities- online universities in which student take classes via the Internet either at home or in an-off-site location. Ex.: University of Phoenix, California Virtual Campus.
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