7.3 THE GLOBAL INTERNET

What is the internet?

• The internet has become the world most extensive, public communication system that now rivals the global telephone system in reach and range.

• It's also the largest implementation of client/server computing and internetworking, linking hundreds of thousand of individual networks and 1 billion people worldwide.

• This global network of networks began in the early 1970s as a U.S department of defense network to link scientists and university professors around the world.

• Individuals connect the internet in 2 ways : through local Internet service providers (ISPs) and through their business firm.

1. Digital Subcriber Line (DSL) technologies operate over existing telephone lines to carry voice, data and video at transmission rates ranging from 385Kbps all the way up to 40Mbps, depending on usage patterns and distance.
2. Cable Internet Connectons provided by cable vendors use digital cable coaxil lines to deliver high-speed internet access to homes and businesess.

7.3.1 Internet addressing And Architecture.

         The Domain Name System

1. The Internet is based on the TCP/IP networking protocol suite. ever computer is assigned a unique Internet Protocol (IP) address, which is currently four strings of numbers ranging from 0 to 255, as in the address 207.46.250.119.
2. The Domain Name system (DNS) is a system for converting IP addresses into names, such as google.com. DNS has hierarchical structure which specifies a root domain, top level domains, second-level domains, and host computers at the third level.

Figure 7.1 The Domain Name System

The common domain extension currently aviable and official approved are shown in the following list :

.com  commercial organisation/businessess
.edu   educational institutions
.gov   U.S goverment instituions

Internet Network Architecture and Governance

• Internet policies are established by several organizations and governmental bodies, including the internet Architecture Board (IAB)
• The Internet Corporation for Assinged Names and Numbers (ICANN)
• The Internet Network Information Center (InterNIC)
• the internet Engineering Task Force (IETF)
• The Internet Society (ISOC)
• The World Wide Web Consortium (W3C)

1. These agencies infleunce goverment agencies, major network owners and ISP.
2. Everyone who uses the internet pays some fee-hidden or otherwise to maintain the network. For example, each organization and business firm pays for its own nerworks and its own local Internet connnection services, a part of which is paid to the long-distance trunk line owners.
3. The Internet Engineering Task Force adopted a new internet Protocol Version 6 (IPv6), which uses a 128-bit addressing scheme which produces 3.4 x 1038 addresses.
4. The existing Internet has many shortcomings chief among which are poor security, no service level guarentees, no differential service, no differential pricing, and bandwidth limitions that would prevent the emergence of wide-scale Internet television or internet (NGI) are consortia 200 unversities, private businesses, and goverment agencies in the United States that are working on a new, robust, high-bandwidth version of the internet.

Figure 7.2 Internet Network Architecture

7.3.2 Internet Services And Communication

1. The Internet is based on client/server techonology. Client paltforms include PCs, cell phones, PDAs, handled devices, and information appliances. Users of the Internet control what services they access through client applications on thier computers such as web browsers. Internet services include e-mail, electronic discussion groups (Usenet groups and LISTSERV), chatting, and instant messaging, Telnet, File Transfer Protocol (FTP), and the World Wide Web.
2. Each Internet service is implemented by one or more software programs.

Example :

• E-mail enables messages to be exchanged from computer to computer, with capabilities for routing messages to multiple recipents, forwarding messages, an attaching text documents or multimedia messages.

• Internet telephony: Voice over IP (Voip) technology uses IP to deliver voice information in digital form using packet switching, avoiding the tolls charged by local and long-distance networks.

Figure 7.3 Client/Server Computing on The Internet

Figure 7.4 HOW IP TELEPHONY WORKS

7.3.3 The web

1. Web pages are formatted with graphics,text, and dyamic links using Hypertext Markup Language (HTML).
2. Web pages are requested by clients and delivered by web servers using the Hypertext Transfer Protocol (HTTP). HTTP is the first set of letters  at the start of every web addres, followed by the Domain name, the directory path to the requested documents, and the document name.
3. The address typed in to a browser to locate file, including the directory path and the document name together is called a Uniform Resource Locator (URL). A web server software for location and managing stored Web pages, the most common Web server today is Apache HTTP Server.

Figure 7.4 A Virtual Private Network Using the Internet.

This VPN is a private network of computers linked using a secure "tunnel" connction over the Internet. It protects data transmitted over the public Internet by encouding the data and "wrapping" them within the Internet Protocol (IP).  By adding a wrapper around a network message to hide its content, organizations can create a private coonnection that travels through the public Internet.

Search Engine

1. Users can find information on the internet using search engines. The first search engines were simple keyword indexes of all the pages visited. Contemporary search engines use more complex models for finding relevant information. Google ranks Search based on the relevance, or popularity, of each page. Web sites for locating information such as Yahoo!, Google, and MSN have become so popular and easy to use that they  also serve as major portals for the internet, as well as major shopping tools. In search engine marketing, search results display both listings to a query as well as major advertisments related to the search query. The paid, sponsered advertisement are the fastest-growing form of Internet advertising.

Figure 7.5 Major Web Search Engines

1. Internet networking technology is used by organization to create private networks called intranets and ectranets, intranets extended to authorized vendors and customers to facilate communication and business transactions. Intranets and extranets are protected from unauthorized visits by Firewalls-security system with specialized software system with specialzed software to prevent outsiders from entering private networks.

Web 2.0 refers to second-generation, interacive Internet-based services, such as :

• Mashups: Software services that enables users and system developers to mix and match content or software components to create something entirely new.
• Blgs : Informal yet structured Web site where subscribing individuals can publish stories, opinions, and links to other web sites of interest.
• RSS: RSS (Rich site Summary, or Really Simple Syndication) technology pulls specifed content from Web sites feeds its automatically to users' computers, where it can be stored for later viewing.
• Wikis: Collaborative Web Sites where visitors can add, delete, or modify content on the site, including the work of previous authors

Web 3.0: The future Web 

web 3.0 is the promise of a future Web where all this digital information, all these contacts, can be woven together into a single meaningful experience. 

7.2 COMMUNICATION NETWORKS

COMMUNICATION NETWORKS

SIGNALS: DIGITAL VS ANALOG

• Analog  signal is  represented by a continiuous waveform that passes thought acommunication medium an has been used for voice communication.
• A digital signal is a discrete,binary waveform, rather than a continuos waveform.
• Digital signals communicate information as strings of two discrete states: one bit and zerobits, which are represented as on–off electrical pulses.
• Called a modem to translate digital signals into analog form.

FIGURE 7.1   Functions of the modem

• A modem is a device that translates digital signals from a computer into analog form so that they can be transmitted over analog telephone lines. The modem also translates analog signals back into digital form for the receiving computer.

Modem

Local area network (LAN)

Type of networks

LOCAL AREA NETWORK(LAN)

• Designed to connect personal computers and other digital devices within a halfmile or 500-metre radius.
•  Connect a few computers in a small office, all the computers in one building, or all the computers in several buildings in close proximity Windows, Linux, and Novell.
•  three major LAN topologies:

1. Star topology :all devices on the network connect to a single hub organized into a hierarchy.
2. Bus topology, one station transmits signals, which travel in both directions along a single transmission segment. All machines on the network receive the same signals, and software installed on the client’s enables each client to listen for messages addressed.
3. Ring topology connects network components in a closed loop.Messages pass from computer to computer in only one direction.

CAMPUS AREA NETWORK(CAN)

•  Up to 1,000 meters(a mile);a college campus or corporate facility.
• CAN is a network of multiple interconnected local area networks (LAN) in a limited geographical area. A CAN is smaller than a wide area network (WAN) or metropolitan area network (MAN).
• CAN benefits are as follows:

1. Cost-effective
2. Wireless, versus cable
3. Multidepartmental network access..
4. Single shared data transfer rate (DTR)

Metropolitan area network(MAN)

• Span broad geographical distances—entire regions, states, continents, or the entire glob.
• Computers connect  through public networks  such as the telephone system or private cable systems, or through leased lines or  satellites.

WIDE AREA NETWORK(MAN)

• A network that spans a metropolitan area,usually a city and its major suburbsIts geographic scope falls between a WAN and a LAN

      

     FIGURES 7.1 NETWORK TOPOLOGIES

• Wide range of speeds is possible for any given medium depending on the software and hardware configuration         

           

  TRASMISSION MEDIA AND TRANSMISSION SPEED

• Networks use different kinds of physical tranmission media:

Transmission media

• Twisted Wire  consists of strands of copper wire twisted in pairs and is an older type of transmission medium.
• The telephone systems in buildings had twisted wires installed for analog communication.
• Used LANs, such as CAT5

Coaxial Cable

• Coaxial cable, similar to that used for cable television, consists of thickly insulated copper wire.
• Transmit a larger volume of data than twisted wire.

Fibre Optics and Optical Networks 

• Fibre optic cable consists of bound strands of clearglass fibre, each the thickness of a human hair.
• Data are transformed into pulses of light,which are sent through the fibre optic cable by a laser device.

Wireless Transmission Media

• Wireless transmission is based on radio signals of various frequenciessed to handles the major traffic.
• Microwave systems ;follow a straight line and do not bend with the curvature of the earth.
• Such as Communication satellites are typically used for transmission in large.

Transmission Speed

• The total amount of digital information that can be transmitted through any telecommunications medium is measured in bits per second.
• Hertz  frequencies that can be accommodated on a particular telecommunications channel is called its bandwidth                                                                                                                   

7.1. TELECOMMUNICATIONS AND NETWORKING IN TODAY'S BUSINESS WORLD.

If we work in a business, we can't do without networks. We need to communicate rapidly with the customers, suppliers and employees. Until about 1990, business used the postal system or telephone system with voice or fax for communication. Today, however, we and employees for example, use computers, e-mail and messaging, the internet, cell phones, and mobile computers connected to wireless networks for this purpose.

      There are two fundamentally different types of networks , that is telephone networks and computer networks. Telephone networks historically handled voice communication, and computer networks handled data traffic.

       Networking and communication trends :-

1. Convergence : the telephone networks and computer networks converging into single digital network using internet standards.
2. Broadband : more than 68% U.S internet users have broadband access.
3. Broadband wireless : voice, data communication are increasingly taking place over broadband wireless platforms.

      

      If we had to connect the computers for two or more employees together in the same office, we would need a computer network.

           Computer Network :-

• Two or more connected computers
• Major components in simple network are :-
•  client and server computers   
•  network interfaces (NICs)   
•  connection medium       
•  network operating system  
•  Hubs, switches, routers  
• Software-defined networking (SDN)
• functions of switches and routers managed by central program

The diagram shows compenents of a simple computer network

Networks in large companies

       The network we have just described above might be suitable for a small business. But, how about for the large companies with many different locations and thousand of employees ? As a firm grows, and collects hundreds of small local area networks, these networks can be tied together into a corporate-wide networking infrastructure.

           Network in large companies are :-

• hundreds of local area networks ( LANs ) linked to firmwide corporate network
• various powerful servers -Web site ,  -Corporate intranet, extranet , -Backend systems
• mobile wireless LANs ( Wi-Fi networks )
• Videoconferencing system
• Telephone network
• Wireless cell phones

Today's corporate network infrastructure is a collection of many different networks from the public switched telephone network, to the internet.