Data communication

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Data communication Data communication Presentation Transcript

  • Data Communication Flow Control by Md.Javedul Ferdous East West University
  • Flow Control Flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node.
  • So why need it ?????
  • Prevent degradation and loss of efficiency due to overload Deadlock avoidance Fair allocation of resources among competing users Speed matching between the network and its attached users.
  • Type of ‘Flow Control’ • Stop-and-wait • Sliding Window
  • Stop-and-wait • Fundamental technique to provide reliable transfer under unreliable packet delivery system • simplest form of flow control • inefficiencies when sending longer transmissions
  • Stop-and-wait
  • Sliding Window • Technique for controlling transmitted data packets between two network computers where reliable and sequential delivery of data packets is required • • Best utilized when the buffer size is limited and pre-established. • Better Performance
  • Levels of Flow Control Hop Level Entry-to-Exit Level Network Access Level Transport Level
  • Hop Level Prevent store and forward buffer congestion and its consequences Maintain a smooth flow of traffic between two neighboring nodes In a computer network
  • Entry-to-Exit Level Implement as a protocol between the source and destination switch Protect the exit node from congestion
  • Network Access Level Throttle external inputs based on measurements of internal network congestion.
  • Transport Level Efficient and reliable transmission of messages within each user session and the efficient sharing of common network resources by several user sessions Events destination buffer congestion and overflow is known as transport level flow control
  • Problem of ‘Flow Control’ Can’t send too slow or too fast Too slow wastes time Too fast can lead to buffer overflow