• A network is any collection of independent computers that communicate with one another over a shared network medium. A computer network is a collection of two or more connected computers.
  • Every network includes:
    1. At least two computers Server or Client workstation.
    2. Networking Interface Card's (NIC)
    3. A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.
    4. Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, Unix and Linux
  • Types of Networks:
    1. LANs (Local Area Networks): A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus.
    2. WANs (Wide Area Networks): Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services.
    3. MANs (Metropolitan Area Networks): It is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN).
    4. Internet: The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups.
    5. Intranet: With the advancements made in browser-based software for the Internet, many private organizations are implementing intranets. An intranet is a private network utilizing Internet-type tools, but available only within that organization.
    6. VPN (Virtual Private Network): VPN uses a technique known as tunneling to transfer data securely on the Internet to a remote access server on your workplace network. Using a VPN helps you save money by using the public Internet instead of making long–distance phone calls to connect securely with your private network.
  • Categories of Internet: Network can be divided in to two main categories:
    • Peer-to-peer: In peer-to-peer networking there are no dedicated servers or hierarchy among the computers. All of the computers are equal and therefore known as peers.
    • Server – based: The term Client/server refers to the concept of sharing the work involved in processing data between the client computer and the most powerful server computer.
  • The OSI Model: Open System Interconnection (OSI) reference model has become an International standard and serves as a guide for networking. This model is the best known and most widely used guide to describe networking environments.
    There are seven layers to get familiar with and these are the
    • Physical layer
    • Data link layer
    • Network layer
    • Transport layer
    • Session layer
    • Presentation layer
    • Application layer
  • A network topology is the geometric arrangement of nodes and cable links in a LAN, There are three topology's to think about when you get into networks. Various Topologies are as follows:
    1. Star: In a star topology each node has a dedicated set of wires connecting it to a central network hub. Since all traffic passes through the hub, the hub becomes a central point for isolating network problems and gathering network statistics.
    2. Ring: In a ring topology features a logically closed loop. Data packets travel in a single direction around the ring from one network device to the next. Each network device acts as a repeater, meaning it regenerates the signal.
    3. Bus: The bus topology, each node (computer, server, peripheral etc.) attaches directly to a common cable. This topology most often serves as the backbone for a network.

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