• 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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