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CHAPTER 1 EXPLORE THE NETWORK, CHAPTER 1.1 Explain LANs,WANs and The…

- - - - Local Area Network (LAN)
      - Wide Area Network (WAN
      - Other types of networks include:
        
        1)Metropolitan Area Network (MAN)
        
        2)Wireless LAN (WLAN)
        
        3)Storage Area Network (SAN
        
        4)Personal Area Network (PAN)
  - - - Extranet: shared content accessed by groups through cross
        enterprise boundaries
      - Intranet: shared content accessed by members within a single organization
  - - - Scalability: Thousands
        of new users and service providers connect to the Internet each week. In order for the Internet to support this rapid amount of growth, it must be scalable. A scalable network can expand quickly to support new users
        and applications and applications without affecting the performance of the service being delivered to existing users.
        
        Quality of Service: Quality
        of service is also an ever increasing requirement of networks today. New applications available to users over internetworks, such as voice and live video transmissions.
        
        Security: Security
        Securing a network infrastructure includes physically securing devices that provide network connectivity, and preventing unauthorized access to the management software that resides on those devices
- - - - it include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received
        
        Networking Protocols
        
        HTTP (Hypertext Transfer Protocol)
        
        application protocol that governs the way a web server and a web client interact
        
        TCP (Transmission Control Protocol)
        
        transport protocols that manages the individual conversation
        
        IP (Internet Protocol)
        
        encapsulates the TCP segments into packets, assigns addresses and delivers to destination host
        
        ETHERNET
        
        allows communication over a data link and the physical transmission of data in the network media
      - TCI/IP
        
        (PROTOCOL SUITE)
        
        open standards, protocols are freely available and any vendor is able to implement these protocols on their hardware/software
        
        (COMMUNICATION PROCESS)
        
        HTTP application layer send data to the transport layer
        
        next, IP source and destination addresses are added which create an IP packet
        
        ethernet information is added creating data link frame
        
        frame is delivered to the nearest router along the path towards the client
        
        COMMUNICATION PROCESS (CONT.)
        The clients processes and removes each protocol header in the opposite order it was added
    - - OSI (Open System Interconnection)
        
        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
        
        6.PRESENTATION -provides for common representation of
        the data
        
        7. APPLICATION-provides services to the presentation layer to
        organize its dialogue and to manage data exchange
        
        PHYSICAL - describe the mechanical, electrical, functional and procedural means to transmit bits across physical connections
      - Benefits of Using a Layered Model
        
        assisting in protocol design since protocols at each layer have defined function
        
        fostering competition because products from different vendors can work together
        
        preventing technology changes in one layer from affecting other layers
        
        providing a common language to describe networking function and capabilities
      - COMPARISION BETWEEN OSI AND TCP/IP
        
        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
        
        difference
        
        protocol standards
        
        combines the presentation and session layer issues into its application layer
        
        combines the OSI data link and physical layers into the network access layer
        
        simpler
      - TCP/IP (Transmission Control Protocol/Internet Protocol)
        
        TRANSPORT - supports communication between diverse devices across diverse networks
        
        INTERNET - determines the best path through the network
        
        APPLICATION - represents data to the user, encoding and dialog control
        
        NETWORK ACCESS - controls the hardware device and media that make up the network
- - - - THE RULES
        
        Message Encoding
        
        Encoding between hosts must be in appropriate format for the medium.
        
        Messages are first converted into bits by the sending host.
        
        Each bit is encoded into a pattern of sounds, light waves or electrical impulses depending on the network media
        
        The destination host receives and decodes the signals in order to interpret the message
        
        message source :arrow_right: encoder :arrow_right: transmitter :arrow_right: transmission medium (the channel) :arrow_right: receiver :arrow_right: decoder :arrow_right: message destination
        
        Message Formatting and Encapsulation
        
        There is an agreed format for letters and addressing letters which is required for proper delivery.
        
        Putting the letter into the addressed envelope is called encapsulation
        
        Each computer message is encapsulated in a specific format called a frame before it is sent over the network.
        
        A frame acts like an envelope providing destination address and source address.
        
        Message Size
        
        Humans break long messages into smaller parts or sentences
        
        Long messages must also be broken into smaller pieces to travel across a network
        
        each piece is sent in a separate frame
        
        each frame has its own addressing information
        
        a receiving host will reconstruct multiple frames into the original message
        
        Message Timing
        
        Access Method
        
        hosts on a network need to know when to beginsending messages and how to respond when collisions occur
        
        Flow control
        
        source and destination hosts use flow control to negotiate correct timing to avoid overwhelming the destination and ensure information is received.
        
        Response timeout
        
        hosts on the network have rules that specify how long to wait for responses ad what action to take if a responses timeout occurs
        
        Message Delivery Options
        
        Unicast Message
        
        one-to-one delivery
        
        -Multicast Message
        
        one-to-many delivery
        
        -Broadcast Message
        
        one-to-all delivery
- - - - 2)
        
        Hardware and Software Management and Administration Costs
        
        3)
        
        Undesirable Sharing
        
        4)
        
        Illegal // Undeirable Behaviour
        
        5)
        
        Data Security Concerns
- - - - 2) SERVER
        
        A computer on the network that manages shared resources
        
        Servers usually have more
        :silhouettes:processing power
        :silhouettes:memory
        :silhouettes:hard disk space
        than clients
        
        1)CLIENT
        
        A computer on the network that requests resources // services from anothe computer on a netwrok
        
        a client could also act as a server
        
        The term client may also refer to the human user of a client workstation // to client software installed on the workstation
    - - 5)NETWORK OPERATING SYSTEM (NOS)
        
        The software that runs on a server & enables the server to manage;
        :star:data
        :star:users
        :star:groups
        :star:security
        :star:applications
        :star:other networking functions
        
        Ex : -Microsoft Windwows Server 2008 R2
        -Mac OS X Server
        -Unix & Linux OS
        
        4)NETWORK INTERFACE CARD (NIC)
        
        The device inside a computer that connects a computer to the network media
        
        Allowing it to communicate with other computers
    - - 8)CONNECTIVITY DEVICE
        
        A specialized device that allows multiple networks // multiple parts of one network to connect and exchange data
        
        9)BACKBONE
        
        The part of a network to which segments & significant share devices such as;
        :star:routers
        :star:switches
        :star:servers
        connect.
        
        A backbone is sometimes referred to as "network of networks" because of its role in interconnecting smaller parts of a LAN or WAN
    - - 11)TOPOLOGY
        
        The physical layout of a computer network. Topologies vary according to the needs of the organization and available hardware & expertise
        
        Networks can be arranged in a;
        :pencil2:ring
        :pencil2:bus
        :pencil2:star formation [most common]
        
        Hybrid combinations of these patterns are also possible
        
        12)PROTOCOL
        
        A format for communication between networked devices
        
        For examples ; some protocols ensure that data are transferred in sequence & without error from one node on the network to another
        
        13)TRANSMISSION MEDIA
        
        The means through which data are transmitted and received
        
        Transmission media may be physical such as
        :check:wire // cable
        :check:atmospheric [wireless]
        :check:radio waves
  - - - :check:ADVANTAGES
        
        Easy to set up
        
        Less complexity
        
        Lower cost since network devices & dedicated servers may not be required
        
        :green_cross:DISADVANTAGES
        
        No centralized administration
        
        Not as secure
        
        Not scalable
        
        All devices may act as both clients & servers which can slow their performance
    - - Another way of designing a network is;
        to use a central computer [server]
        ( to facilitate communication & resource sharing between other computers on the network [clients] )
        
        A network that uses a server to enable clients to share;
        :silhouettes:data
        :silhouettes:data storage space
        :silhouettes:devices [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 & processing
        
        Client//Server Networks