INTRODUCTION TO
INFORMATION SYSTEMS
Chapter4.
Tele Communication and network
computing(Cont..)
The International Standards Organization open systems interconnection protocol (ISO-OSI)
The ISO-OSI model defines how software on different system communicates at different layers. The model has seven layers, each having its own well-defined function.
Layer 1: physical layer: define the mechanism for
communicating with the transmission media and interface hardware.
Layer 2: data link layer: validates the integrity of the flow of data.
Layer 3. network layer: defines the protocols for data routing to ensure that information arrives at the correct destination
The International Standards Organization open systems interconnection protocol (ISO-OSI) cont…
Layer 4: transport layer: defines the protocols for structuring messages.
Layer 5: session layer : coordinates communications and maintains the session for as long as needed including security and log-on functions.
Layer 6: presentation layer; defines the way data is formatted, converted and encoded
Layer7: application layer. Defines the way that
applications programs such as e-mail interact with the network
TG
Network Topologies
• Topology refers to the way in which the network of computers is connected.
• Star, all network nodes connect to a single computer, typically the file server.
• Bus, all network nodes connect to the bus, which is a single communications channel, such as twisted pair, coaxial cable, or fiber optic cable.
• Ring, network nodes are connected to
adjacent nodes to form a closed loop.
Network Topologies
The Internet
• Internet (“the Net”) is a global WAN that connects approximately 1 million internal organizational
computer networks in more that 200 countries on all continents.
• ARPANET
– An experimental project started by the U.S.
Department of Defense (DoD) in 1969
– To share data, exchange messages, transfer files.
Internet Technologies
• Intranet is a network designed to serve the internal informational needs of a single
organization.
• Extranet connects part of the intranets of
different organizations and allows for secure communications among business partners over the Internet using virtual private
networks.
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Internet Technologies (Continued)
• Virtual private network (VPNs) are private communications networks that use the
internet for transmission.
Darknets
• Darknets are private networks that run on the Internet but are open only to users who
belong to the network.
• Three major uses:
– Freedom of speech where censorship exists;
– Corporate security to protect sensitive data;
– Copyright infringement - file-sharing software.
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Operations of the Internet
• Internet Protocol (IP) the set of rules used to send and receive packets from one machine to another over the Internet.
• Packet switching is a transmission technology
that breaks up blocks of text into small, fixed
bundles of data called packets.
Assessing the Internet
• Connecting via an Online Service by opening an account with an Internet Service Provider.
– Internet Service Provider (ISP) is a company that offers Internet connections for a fee. Examples are AOL, Comcast, Verizon.
– Network access points (NAPs) are an exchange point for Internet traffic. NAPs are key
components of the Internet backbone.
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Assessing the Internet (Continued)
• Connecting via Other Means by making assess to the Internet cheaper, faster and easier.
– Internet Kiosks are terminals located in public
places like libraries and airports for people who do not have computers.
– Internet assess from cell phones, pagers and even connecting via satellite.
Addresses on the Internet
• Each computer on the Internet has an assigned address, called an IP address.
(i.e. 135.62.128.91)
• Domain Name System (DNS) the naming system for IP addresses of companies.
• Domain names consist of multiple parts,
separated by dots, which are read from right to left. (i.e. www.internic.com)
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The Future of the Internet
• Internet2 develops and deploys advanced network applications such as remote medical diagnosis, digital libraries, distance education, onine simulation and virtual libraries www.Internet2.edu
• Next Generation Internet (NGI) government
sponsored initiative aimed at creating an Internet that is fast, always on, everywhere, natural,
intelligent, easy and trusted. www.ngi.gov
• vBNS is a high-speed network designed to support the academic Internet2 and the NGI initiatives.
5.3 The World Wide Web
• World Wide Web (the Web, WWW, W3) is a system of universally accepted standards for storing,
retrieving, formatting and displaying information via a client/server architecture and a graphical user
interface.
• Home page is a text and graphical screen display that welcomes the user and explains the organization that has established the page.
• Web site is all the pages of the organization.
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WWW (continued)
• Webmaster the person in charge of the organization’s Web site.
• Uniform resource locator (URL) points to an address of a specific resource on the Web.
• Hypertext transport protocol (HTTP) is the
communications standard used to transport
pages across the Web portion of the Internet.
WWW (Continued)
• Browsers provide a graphical front end that enable users to point-and-click their way
across the Web, a process called surfing.
– Provide a uniform interface regardless of operating system.
– Leading browsers are Microsoft’s Internet
Explorer, Mozilla’s Firefox, Netscape Navigator.
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