M01 Intro to Data Communication

• •Data communications ◦The movement of computer information from one point to another by means of electrical or optical transmission systems
• •Telecommunications ◦A broader term that includes the transmission of voice and video (images and graphics) as well as data; usually implies longer distances
• •Data communications networks ◦Facilitate more efficient use of computers and improve the day-to-day control of a business by providing faster information flow◦Provide message transfer services to allow computer users to talk to one another via email, chat, and video streaming•Data communications and networking technologies operate globally.
• •Client: the input-output hardware device at the user’s end of a communication circuit•e.g., desktops, laptops, tablets, cell phones, etc.
• Server: a device that stores and transmits data to a client•e.g., Web server, mail server, file server
• •Circuit: a pathway or connection between client and server through which messages travel•e.g., copper wire, fiber optic cable, wireless•Connections created by switches, cables, router (router connects two or more networks)
• •Peer-to-peer networks: networks designed to connect a set of similar computers that share their data and software with each other
• Components of a Typical LAN 

  
• •Local area networks (LANs)◦Covers a small, clearly defined area◦Might contain a single floor or work area or single building◦When LANs use wireless circuits, they are called Wireless Local Area Networks (WLAN)
• •Backbone networks (BNs)◦High-speed networks connecting other networks together◦May span hundreds of feet to several miles
• •Wide area networks (WANs)◦Largest geographic scope◦Often composed of leased circuitsMay spans hundreds or thousands of miles
• Types of Networks

  
• •Intranet◦A network (often a LAN) that uses the Internet technologies to share information within an organization◦Open only those inside the organization◦e.g., employees accessing budgets, calendars, and payroll information available through the organization’s intranet
• •Extranet ◦A network that uses the Internet technologies to share information between organizations◦Accessible through the Internet◦Open only those invited users outside the organization◦e.g., suppliers and customers accessing the inventory information of a company over an extranet
• •Network models divide communication functions into layers.•The two most known models◦Open Systems Interconnection Reference Model (OSI model)◦Seven layers◦A more conceptual, reference model to illustrate the entire communication pathway◦Internet Model (TCP/IP model)◦Five layers◦A simplified implementation of the OSI model widely used in practice
• Network Models – The OSI and Network Models Compared

  
• •Protocols: define the language of transmission◦Specify the rules, functionality, and messages for communication at the layer
• •Protocol data unit (PDU): contains layer-specific information necessary for a message to be transmitted through a network◦Each layer adds a PDU.◦PDUs act like nested envelopes.◦Encapsulation occurs when a higher level PDU is placed inside of a lower level PDU.
• OSI: Mapping to PDUs (Data Units) and Protocols

  
• Internet Model: Mapping of PDUs and Protocols

  
• •Standards are necessary to:•Ensure that hardware and software produced by different vendors can work together and “speak the same language”•Develop networks that can link to each other and easily share information•Allow customers to have access to more than one vendor•Promote competition, discourage monopolies, and keep a hold on pricing
• •De jure standards


  ◦Formalized by an industry or government body◦e.g., HTTP, IEEE 802.3, 802.11n
• •De facto standards


  ◦Widely accepted, but not formalized◦e.g., Microsoft Windows◦Often become de jure standards eventually
• •De jure standardization process

  
• •As aligned to the Internet Model

  
• •Standards-setting organizations• International Organization for Standardization (ISO)

  •International Telecommunications Union – Telecommunications Group (ITU-T)• American National Standards Institute (ANSI)• Institute of Electrical and Electronics Engineers (IEEE)
• •Standards-setting organizations: Internet Engineering Task Force (IETF) 


  – publishes Internet protocol RFCs•Standards often operate simultaneously, and therefore, translations between standards must also take place.
• Implications for cyber security

  •Ease of access to networks and devices across the world pose great risks.◦ Device security◦ Information privacy◦ Data integrity and transfer◦ Secure storage and server space
• Implications for Cyber Security

  •Ease of access to networks and devices across the world pose great risks.◦Device security◦ Information privacy◦ Data integrity and transfer◦ Secure storage and server spaceTo learn more about risks to networks, read (optional) this article on the