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Chapter 1: Explore The Network, The Internet, Communication methods, a.…

- - - - Application - contains protocols used for process-to-process communications.
        Presentation - provides for common representation of the data.
        Session - provides services to the presentation layer to organize its dialogue and to manage data exchange.
        Transport - defines services to segment, transfer, and reassemble the data.
        Network - provides services to exchange the individual pieces of data over the network between identified end devices.
        Data Link - provides methods for exchanging data frames
        between devices over a common media.
        Physical - describes the mechanical, electrical, functional, and procedural means to transmit bits across physical connections.
    - - The TCP/IP Protocol
        Model:
        ◦ Created in the early
        1970s for internetwork communications.
        ◦ Open Standard.
        ◦ Also called The TCP/IP Model or the
        Internet Model.
    - - In the OSI model, the network access layer and the application layer of the TCP/IP model are further divided to describe discrete functions that must occur at these layers.
        
        :
        
        Similarities:
        
        Share similar architecture.
        
        Share a common application layer
        
        Both models have comparable transport and network layers.
        
        Knowledge of both models is required by networking professionals.
        
        Differences:
        
        Protocol standard
        
        combines the presentation and session layer issues into its application layer
        
        combines the OSI data link and physical layers into the network access layer
        
        A simpler model
- - - - When sending data from a web server to a client the encapsulation procedure would be as follows:
        ◦ The webserver prepares the Hypertext Markup Language (HTML) page. The HTTP application layer protocol sends the data to the transport layer.
        ◦The transport layer breaks the data into segments and identifies each.
        ◦ Next the IP source and destination addresses are added, creating an IP Packet.
        ◦ The Ethernet information is then added creating the Ethernet Frame, or data link frame.
        
        • This frame is delivered to the nearest router along the path towards the web client. Each router adds new data link information before forwarding the packet.
      - When receiving the data link frames from the web server, the client processes and removes each protocol header in the opposite order it was added:
        ◦ First the Ethernet header is removed
        ◦ Then the IP header
        ◦ Then the Transport layer header
        ◦ Finally the HTTP information is processed and sent to the client’s web browser
  - - - Network Protocols
        
        The role of protocols
        How the message is formatted or structured
        The process by which networking devices share information about pathways with other networks
        How and when error and system messages are passed between devices
        The setup and termination of data transfer sessions
      - Protocol Interaction
        Communication between a web server and web client is an example of an interaction between several protocols:
        ◦ HTTP - an application protocol that governs the way a web server and a web client interact.
        ◦ TCP - transport protocol that manages the individual conversations.
        ◦ IP – encapsulates the TCP segments into packets, assigns addresses, and
        delivers to the destination host.
        ◦ Ethernet - allows communication over
        a data link and the physical transmission of data on the network
        media.
- - - - Advantage of Coumputer Network
        
        Networks enable multiple users to share resources (devices and
        data)
        
        Saves money.
        
        Saves time
        
        Network allow you to manage, or administer, resources on
        multiple computers from a central location.
      - Disadvantage of Computer Networks
        
        Network Hardware, Software and Setup Costs
        
        Hardware and Software Management and Administration Costs
        
        Undesirable Sharing
        
        Illegal or Undesirable Behaviour
  - - - A computer on the network that requests resources or services
        from another computer on a network.
      - In some cases, a client could also act as a server. The term client may also refer to the human user of a client workstation or to client software installed on the workstation.
    - - A computer on the network that manages shared resources.
      - Servers usually have more processing power, memory, and hard disk space
        than clients.
      - Server run network operating software that can manage not only data, but
        also users, groups, security, and applications on the network.
    - - A personal computer (such as a desktop or laptop), which may
        or may not be connected to a network; most clients are
        workstation computers.
    - - The device inside a computer that connects a computer to the
        network media
      - Thus allowing it to communicate with other computers
    - - The software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions.
      - Example: Microsoft Windows Server 2008 R2, Mac OS X Server, Unix and Linux OS.
    - - A computer that enables resource sharing by other computers
        on the same network.
    - - A client, server, or other device that can communicate over a network and that is identified by a unique number, known as its network address.
    - - A specialized device that allows multiple networks or multiple
        parts of one network to connect and exchange data.
    - - The part of a network to which segments and significant shared
        devices (such as routers, switches, and servers) connect.
      - A backbone is sometimes referred to as “a network of networks” because of its role in interconnecting smaller parts of a LAN or WAN.
    - - A part of a network. Usually, a segment is composed of a group of nodes that use the same communications channel for all their traffic
    - - The physical layout of a computer network. Topologies vary according to the needs of the organization and available hardware and expertise.
        
        Networks can be arranged in a ring, bus, or star formation, and the star formation is the most common.
        
        Hybrid combinations of these
        patterns are also possible.
    - - A format for communication between networked devices.
      - For example, some protocols ensure that data are transferred in sequence and
        without error from one node on the network to another.
    - - The means through which data are transmitted
        and received.
      - Transmission media may be physical, such as wire or cable,
        or atmospheric (wireless), such as radio waves.
    - - Client/Server
        Networks
        
        Another way of designing a network is to use a central computer, known as a server; to facilitate communication and resource sharing between other computers on the network, which are known as clients.
        
        A network that uses a server to enable clients to share data, data
        storage space, and devices is known as a client/server network.
        
        A client/server architecture is sometimes used to refer to the design of a network in which clients rely on servers for resource sharing and processing.
      - Peer-to
        -Peer Networks (P2P)
        
        Advantages
        
        Easy to set up
        
        Less complexity
        
        Lower cost since network devices and dedicated servers may not be required
        
        Can be used for simple task such as transferring fles and sharing printers
        
        Disadvantages
        
        No centralized administration
        
        Not scalable
        
        All devices may act as both clients and servers which can slow their performance
        
        Not as secure
- - - - a. Extranet
        shared content accessed by groups through cross-enterprise boundaries
        
        b. Intranet
        shared content accessed by members within a single organization