Introduction to Communication Network and Internet

  • Data communication deals with the transmission of signals in a reliable and efficient manner.
  • Data Communication Study Area:
    • Signal transmission
    • Transmission media
    • Signal encoding
    • Interfacing
    • Data link control
    • Multiplexing

Data Communication and Networking for Today’s Enterprise

  • There are three different forces that driven the architecture and evolution of data communication:
    • Traffic growth: seeking for maximizing transmission capacity and minimizing costs
    • Development of new services
    • Advances in technology: advanced in technology that should support growth of traffic an services
  • Technology Trends in Data Communication and Networking:
    • Faster and cheaper in computing and communication
    • Voice-Oriented telecommunications networks (such as PSTN and data networks) are more intelligent
      • The intelligence appears in two areas:
        • Offers of different QoS. As specifications for maximum delay, minimum throughput…
        • Supports variety of customization services in the areas of network management and security
    • Internet, web and associated applications have emerged as dominant features of business and personal world
    • Increasing mobility for librating workers. Which results in voice mail, remote data access …
  • Requirements for High-Speed LANs:
    • Centralized Server Farms: ability to centralize data for multiuser access
    • Power Workgroup: ability to send large amounts of data
    • High-Speed Backbone: ability for high transferring speed
  • Fundamental purpose of a communication system is the exchange of data between two parties

Simple Model of Communication

  • Key Tasks in Data Communication System:
    • Utilization of Transmission System:
      • Need for efficient utilization of transmission facilities shared among communication devices
      • Used Techniques:
        • Multiplexing:
          • Techniques
            used to allocate the total capacity of a transmission medium among several users
        • Congestion Control:
          • Techniques used to assure that the system is not overwhelmed by excessive demands for transmission services
    • Interface; point of connection between devices:
      • Mechanical Characteristics: Shape, # of pins …
      • Electrical Characteristics: values of volts …
      • Functional Characteristics: function (task) of the pin
      • Procedural Characteristics: the set and sequence of function to do a specific task (i.e. printing)
    • Signal Generation:
      • Responsible for generating signals. Here are signal characteristics:
        • Signal should be capable of being propagated through transmission system
        • Signals should be interpretable as data at the receiver
    • Synchronization:
      • Receiver must be able to determine the beginning and duration of each signal element
    • Exchange Management
      • If data are to be exchanged in both directions over a period of time, the two parties must cooperate
    • Error Detection and Correction:
      • Duo to non-perfect medium, a signal may be destroyed during transmission, So there must be a mechanism of detecting and correcting destroyed signals
    • Flow Control:
      • A receiver has limited resources (as buffers), so there must be some source control on the transmission so that the receiver buffers are not flooded
    • Addressing and Routing:
      • Using protocols. A protocol is grading rules to do a specific task
      • Each device must be assigned a unique identifier in the network to enable data transmission
    • Recovery:
      • The network must be able to recover from any failure duo to overload or other cases. No loss of data should occur
    • Message Formatting:
      • There should be a pre-specific format for messages that are transmitted over networks that’s defined by the communication protocol
      • Pre-specific pattern of signals must be exist between transmitter and receiver
    • Security:
      • Sender may wish to assure that only intended receiver received. A received wish to ensure that the received data has not been altered in transit
    • Network Management:
      • How to configure systems.
      • How to react to failure.
      • How to plan for future scalability.
  • The building block of any communications facility is the transmission line.
  • The common communication mediums are fiber optic and wireless transmission.
  • Wireless transmission provides two important concepts:
    • Universal personal telecommunication:
      • Ability of a person to identify himself easily and to use conveniently any communication system in a large area in terms of a single account.
    • Universal Access to Communications:
      • Capability of using the same terminal in multiple environments to connect to information services
  • Transmission services remain the most costly component of a communication budget
  • There are 2 common techniques used to increase the efficiency of transmission services:
    • Multiplexing: ability of a number of devices to share a transmission facility
    • Compression: ability to squeeze data down in order to get lower capacity, cheaper transmission facility
  • Most commonly used transmission media are twisted-pair lines, coaxial cable, fiber cable, and terrestrial and satellite microwave.
  • Error rate depends on signal and medium type to be used.
  • Multiplexing Techniques:
    • Frequency division
    • Synchronous time division
    • Statistical time division

Networks

  • Integration means that the customer equipment and networks can deal simultaneously with voice, data, image and even video
  • Network Types: WAN, LAN and Wireless
  • WAN Implementation Techniques:
    • Circuit Switching:
      • Here a dedicated communication path is established between two stations through network nodes
      • Example: telephone network
    • Packet Switching:
      • There’s no dedicated network path. Data are sent out in sequence of small chunks called packets
      • This technique is commonly used for terminal-to-computer and computer-to-computer communications
    • Frame Relay:
      • Reducing size of packets because the advance in the communication technologies that leads to low error rate
      • Packet switching was designed for users with 64 kbps whereas frame relay designed for up to 2 Mbps
    • Asynchronous Transfer Mode (ATM) – Cell Relay Mode:
      • Frame relay uses variable frame lengths whereas ATM used fixed frame length. This fixed frame called cell
      • This technique is designed to work in range 10s and 100s of Mbps and in Gbps range
  • Differences between WAN and LAN:
    • LAN scope is smaller than WAN scope
    • Usually LAN is owned by an organization. This leads to:
      • Care when choosing LAN because there may be substation investment for purchasing and maintenance.
      • Network management responsibility for a LAN falls solely on the user
    • Internet data rates of LAN are much greater than WAN
  • LAN Types:
    • Switched LAN:
      • Switched Ethernet: consists of a single switch with a number of attached devices or number of interconnected switched
    • Wireless LAN
    • ATM LAN
    • Fiber Channel

The Internet

  • Purpose of the internet is to interconnect end systems called hosts
  • IP datagrams (IP packets) beaked data from source that will be sent over network
  • Central Office
    the place where telephone companies terminate customer lines and locate switching equipment to interconnect those lines with other networks
  • Customer Premises Equipment (CPE): telecommunications equipment that is located on the customers physical location rather than on the providers physical location or in between
  • Internet Service Provider (ISP): company that provides other companies or individuals with access to the internet
  • Network Access Point (NAP): technique that is used to tie all ISPs together
  • Network Service Provider(NSP): company that provides backbone service to ISP
  • Point of Presences (POP): site that has a collection of telecommunication equipment usually refers to ISP or telephone company sites. An ISP POP is the edge of the ISP’s network; connections from users are accepted and authenticated here

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