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TOPIC 1.3: INTERPRET REFERENCE MODEL OF OSI AND TCP/IP, The webserver…

- - - - Transmitter
        
        Transmission Medium
        
        Receiver
        
        Message Destination
  - - - SENDER - It is the device which sends the data messages. It can be a computer, workstation, telephone handset etc.
        
        RECEIVER - It is the device which receives the data messages. It can be a computer, workstation, telephone handset etc.
        
        TRANSMISSION MEDIUM - It is the physical path by which a message travels from sender to receiver. Some examples include twisted-pair wire, coaxial cable, radio waves and etc.
        
        PROTOCOL - It is a set rule that governs the data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating.
  - - - An identified sender and receiver
        
        Common language and grammar
        
        Speed and timing of delivery
        
        Confirmation or acknowledgment requirements
    - - Message encoding
        
        Message delivery options
        
        Message Formatting and Encapsulation
        
        Message timing
        
        Message size
        
        Long messsages must also be broken into smaller pieces to travel across a network.
        
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        Humans break long messages into smaller parts or sentences.
        
        ACCESS METHOD - Hosts on a network need to know when to begin sending messages and how to respond when collisions occur.
        
        FLOW CONTROL - Source and desntinastion hosts use flow control to negotiate correct timing to avoid overwhelming the destination and ensure information is received.
        
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        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.
        
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        Unicast Message ( One-to-one delivery )
        
        Multicast Message ( One-to many delivery )
        
        Broadcast Message ( One-to-all delivery )
        
        Encoding between hosts must be in appropriate format
        
        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.
  - - - DESTINATION (RECEIVER) - The destination receives the message and interprets it.
        
        CHANNEL (MEDIA) - Provides the pathway over which the message can travel from source to destination.
- - - - Agreed-upon medium or channel (face-to-face, telephone, letter, photograph)
        
        Appropriate communication mode (spoken, written, illustrated, interactive or one-way)
        
        Common language
        
        Grammar and sentence structure
        
        Speed and timing of delivery
  - - - Some common networking protocols are Hypertext Transfer Protocol (HTTP), Transmission Control Protocol (TCP), and Internet Protocol (IP).
    - - 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
  - - - 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
  - - - The TCP/IP protocol suite is an open standard, the protocols are freely available, and any vendor is able to implement these protocols on their hardware or on their software.
    - - Application Layer
        
        Transport Layer
        
        Internet Layer
        
        Network Access Layer
      - TCP/IP COMMUNICATION PROCESS
        
        When sending data from a web server to a client the encapsulation procedure would be as follows:
        
        When receiving the data link frames from 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
- - - - Fostering competition because products from different vendors can work together.
        
        Preventing technology changes in one layer from affecting others layer.
        
        Providing a common language to describe networking functions and capabilities.
  - - - PRESENTATION - provides for common representation of the data.
        
        SESSION - provides services to he 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 individuals 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.
  - - - Open Standard.
        
        Also called The TCP/IP Model or the Internet Model.
    - - TRANSPORT - supports communication between diverse devices across diverse networks.
        
        INTERNET - determines the best path through the network.
        
        NETWORK ACCESS - controls the hardware devices and media that make up the network.
  - - - share similar architecture.
        
        share a common application layer.
        
        both models have a 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 network access layer.
        
        a simpler model.