Computer Networks

What is a Network?

Network: A connected system of objects or people

Computer network: A collection of computers and other hardware devices connected together so that users can share hardware, software, and data, as well as electronically communicate with each other.

Internet: Largest computer network in the world

Types of networks:
    Business networks,
    Phone networks,
    Home
    Multimedia networks

Common Uses for Computer Networks
  1. Sharing a printer or an Internet Connection among several users.
  2. Sharing application software with a network license, which can be purchased less expensively and which  needs to be installed and updated on only one computer.
  3. Working collaboratively, such as sharing a company database or using a collaboration tools to create or   review documents.
  4. Exchanging files among network users and over the internet
  5. Connecting the home computers and the entertainment devices, (such as TVs, gaming consoles, and stereo systems) located within a home.

Networking and Communications Applications:

1. Global positioning system (GPS): Uses satellites and a receiver to the exact geographic location of the receiver
  a. Commonly found in cars today
  b. Available as handheld units
  c. Used by the military, hikers, travelers, and others who need to know their precise

2. Videoconferencing: Use of communications technology for real-time, face-to-face meetings between individuals located in different places
  a. Technology continues to improve and mimic reallife environments
  b. Telepresence videoconferenceing
  c. Online conferencing ( via the Internet)
  d. Video phone calls

Types of Network Topology: How the devices in the network (called nodes) are arranged
  1. Star networks: All devices connect to a central device or hub)
      - All computers/devices connect to a central device called hub or switch.
      - Each device requires a single cable
      - Point-to-point connection between the device and hub.
      - Most widely implemented
      - Hub is the single point of failure

  2. Bus networks: All devices connect to a central cable
      - Uses a trunk or backbone to which all of the computers on the network connect.
      - Systems connect to this backbone using T connectors or taps.
      - Coaxial cablings ( 10Base-2, 10Base5) were popular options years ago.

  3. Ring networks: Devices connect to one another in a ring
      a. Logical ring
          -Meaning that data travels in circular fashion from one computer to another on the network.
      - Ring networks are most commonly wired in a star configuration
      - Token Ring has multi-station access unit (MSAU),equivalent to hub or switch. MSAU performs the     token circulation internally.

  4. Mesh networks: Multiple connections between devices
      - Each computer connects to every other.
      - High level of redundancy.
      - Rarely used.
      - Wiring is very complicated
      - Cabling cost is high
      - Troubleshooting a failed cable is tricky
      - A variation hybrid mesh
      - create point to point connection between specific network devices, often seen in WAN
         implementation.
  5. Some networks use a combination of topologies

Internet Terms to be Familiar with:
Browser - Contains the basic software you need in order to find, retrieve, view, and send information over the Internet.

Download - To copy data from a remote computer to a local computer.

Upload - To send data from a local computer to a remote computer.

E-mail - (electronic mail) is the exchange of computer-stored messages by telecommunication. E-mail can be distributed to lists of people as well as to individuals. However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams.

Home Page - The beginning "page" of any site.

HTML (HyperText Markup Language) - The coding language used to create documents for use on the World Wide Web. There are three-letter suffixes used in coding that help to identify the type location one is viewing

HTTP (HyperText Transport Protocol) - the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. Relative to the TCP/IP suite of protocols (which are the basis for information exchange on the Internet), HTTP is an application protocol.
¨Search Engine - A web server that collects data from other web servers and puts it into a database (much like an index), it provides links to pages that contain the object of your search.

TCP/IP - TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP program just as every other computer that you may send messages to or get information from also has a copy of TCP/IP.

URL (Uniform Resource Locator) - The Internet address. The prefix of a URL indicates which area of the Internet will be accessed. URLs look differently depending on the Internet resource you are seeking.

WWW (World Wide Web) - A technical definition of the World Wide Web is: all the resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP).

Internet
- An information system
- Communication tool
- A large network of computer systems world wide can be explored by using a Web Browser
- Services available through the Internet:
    - Email (Discussion groups,Chat Rooms, etc.)
    - Information search (including research)
    - Education (Online courses; virtual colleges)
    - Entertainment, News, and more…...

Evolution of the Internet
ARPANET: The predecessor of the Internet, named after the Advanced Research Projects Agency (ARPA), which sponsored its development
    - Initially connected four supercomputers
    - Eventually grew into today’s Internet

The World Wide Web: The collection of Web pages available through the Internet
    - Proposed by Tim Berners-Lee in 1989
    - Originally only text-based content
    - Release of the graphical Mosaic browser in 1993 led to graphical content
    - Wide variety of content available via Web pages today

Internet: Researches advanced Internet applications and technologies

Web Browsers
- You use this software to view different locations on the Web, which are known as Web pages. A group of Web pages is a Web site. The first page of a Web site is often called the home page.

- Software programs used to access the World Wide Web (WWW)
- Most popular web browsers:
      a. Google Chrome
      b. Microsoft Internet Explorer
      c. Mozilla Firefox
      d. Apple Safari

Search Engines
- A program that connects you to a database or Web address
- used to perform a thorough search
- Some Popular Search Engines
- Google search, Alta Vista, Excite, Hotbot, Lycos, InforSeek, etc.
- Random Browsing (takes too much time)
- Mark Favorite Sites (bookmark the sites)
- Use several Search Engines for a thorough search

Some Well Known Search Engines
- Yahoo! Search
www.yahoo.com

- Google Search
www.google.com

- Bing ”Live Search, Windows Live Search, and MSN Search”
www.bing.com

Email
- E-mail stands for Electronic Mail.
- It is one of the most widely used features of the Internet.
- Mails are regularly used today where with the help of postage stamp we can transfer mails anywhere in the    world.
- With electronic mail the service is similar but here data are transmitted through Internet and therefore within    minutes the message reaches the destination anywhere in the world.

Email Components
- You may have an e-mail account through a business network or you may create an e-mail account with a service that provides Internet access.
- An e-mail address consists of:
   a. A user name or login ID
   b. The “at” symbol (@)
   c. The name of the e-mail server

Understanding Email
- E-mail, or electronic mail, is an efficient way to exchange messages with others on a network.
- This network may be small and self-contained, such as within an office, or as large as the Internet.
- E-mail messages can go to only one recipient or to dozens of recipients at once.
- When you send a message, it travels through the network to an e-mail server.
- The e-mail server stores messages until the recipient(s) request them.

Web Address (URLs)
- Each computer on the Internet has an unique identification number, called an IP (Internet Protocol)               address.

- Each part of the address is a number ranging from 0 to 255, and each part is separated from the previous
  part by a period, for example: 106.29.242.17.

- Although each computer connected to the Internet has a unique IP address, most Web browsers use domain name addressing to locate Web sites and pages.