C5

• Software


  Programs that control data transmission in a network

  
• Protocol


  A set of rules that defines how two devices communicate each other over a network
• Protocols


  • Define how data is transmitted, received, and processed between devices or systems in a network
  • Have 3 key elements: syntax, semantics, timing
• Standard


  A set of specifications and guidelines that define how a particular technology or system should operate
• Standards provide a framework for ensuring interoperability, compatibility, and consistent implementation across different devices and vendors
• Standards are developed by organizations such as the Institute of Electrical and Electronics Engineers (IEEE), International Organization for Standardization (ISO) and Internet Engineering Task Force (IETF)
• OSI Model


  A layered framework for the design of network systems that allows communication between all types of computer systems

  
• The OSI model was first introduced in the late 1970s
• The International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards
• OSI Model


  • Consists of seven separate but related layers, each of which defines a part of the process of moving information across a network
  • The Application Layer (Layer 7) is considered to be the top; the Physical Layer (Layer 1) is the bottom
  • The Transport Layer (Layer 4) is responsible for isolating the function of the lower layers from the higher layers

  
• OSI Model Layers


  • The upper layers deal with application issues and are generally implemented only in software
  • The lower layers handle data transport issues and are implemented in hardware and software, except for physical layer in hardware only

  
• Physical Layer (Layer 1)


  1. Responsible for transmission of bits

  2. Describes the physical properties of the various communications media
• Data Link Layer (Layer 2)

  1. Responsible for ensuring error-free, reliable transmission of data

  2. Determines if errors occurred during transmission and can request retransmission or correction
• Network Layer (Layer 3)


  1. Responsible for setting up the appropriate routing of messages throughout the network

  2. Concerned with types of switching networks used for routing data between networks

  
• Transport Layer (Layer 4)


  1. Responsible to identify the address of receiving computer, monitor the quality of the communication channel and select the most efficient communication service

  2. Defines if and how retransmissions will be used to ensure data delivery

  3. Sets priorities of messages and error recovery procedures
• Session Layer (Layer 5)


  1. Establishes and maintains the connection between two communicating computers

  2. Establishes, maintains and synchronizes the interaction among communicating systems
• Presentation Layer (Layer 6)


  1. Describes the syntax and semantics of the information exchanged between two systems

  2. Provides translation format and code conversion services

  3. Performs encryption and data compression
• Application Layer (Layer 7)


  1. Enables the end user, whether human or software, to access the network

  2. Provides user interfaces and support for services such as electronic mail, remote file access and transfer, shared database management, and other types of distributed information services