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Stop and Wait arq Stop and Wait arq Presentation Transcript

  • GROUP B
  • TEAM MEMBERS
    • GROUP 14: INDIGO
    • AMULYA GURURAJ 1MS07IS006
    • BHARGAVI C S 1MS07IS013
    • MEGHANA N 1MS07IS050
    • TANUSHREE A G 1MS07IS139
    • GROUP 21: DYNAMIC NETWORKS
    • AMEET GONDALI 1MS07IS003
    • BHUJANG R 1MS07IS016
    • KAUSHIK N 1MS07IS037
    • PRAMOD M 1MS07IS070
  • CONTENTS
    • Introduction
    • Stop And Wait ARQ
    • Sender Algorithm.
    • Receiver Algorithm
    • Efficiency
    • Advantages & Disadvantages
    • Applications
    • Demo
  • INTRODUCTION
    • Data Communication channels are divided into two major types :-
    • (a)Noisy Channels.
    • (b)Noiseless Channels.
    • Noiseless Channels :- An ideal case channel put forth by Niquest.
    • Noisy Channel :- Practical case channels , put forth by Shannon.
  • Continued
    • Noiseless Channels :-
    • (1) Simplest
    • (2) Stop and Wait
    • Noisy Channels
    • (1) Stop and wait ARQ
    • (2) Go Back N ARQ
    • (3)Selective Repeat ARQ
  • STOP AND WAIT ARQ
    • Design
    • Implementation .
  • SENDER ALGORITHM
    • Sn =0
    • cansend = true;
    • While(true)
    • {
    • WaitForEvent();
    • If(event(RequesTtoSend) AND cansend)
    • {
    • Getdata();
    • MakeFrame(Sn);
    • StoreFrame(Sn);
    • SendFrame(Sn);
    • StartTimer();
    • Sn =Sn+1;
    • Cansend =false;
    • }
  • SENDER ALGORITHM (CONT..)
    • WaitForEvent();
    • if( event ( Arrival notification))
    • {
    • ReceiveFrame(ackno);
    • If(not corrupted AND ackno == Sn)
    • {
    • Stop Timer();
    • PurgeFrame(Sn-1)
    • cansend =true;
    • }
    • }
    • If(event(Timeout))
    • { StartTimer();
    • ResendFrame(Sn-1);
    • }
    • }
  • RECEIVER SIDE ALGORITHM
    • Rn =0;
    • While(true)
    • { WaitForEvent();
    • If(event(ArrivalNotification))
    • {
    • ReceiveFrame();
    • If( corrupted ( Frame));
    • Sleep();
    • If ( seqNo ==Rn)
    • {
    • Extract data();
    • Deliver data();
    • Rn =Rn+1;
    • }
    • SendFrame(Rn);
    • }
    • }
  • EFFICIENCY
    • Performance Analysis of Stop and Wait ARQ
    • Parameters:
    • TRANSF : Frame transmission time at sender side
    • TRANSA : ACK transmission time at receiver side
    • PROP : propagation delay
    • PROC : Frame processing time
    • p : Probability of frame error at sender side
    • q : Probability of frame error at receiver side
    • TIMEOUT : Sender time out
  • Calculations
    • Case 1 : Efficiency in transmitting an error free packet
    • Time taken to transmit an error free packet is:
    • Ts = TRANSF + TRANSA + 2(PROC+PROP)
    • In this case efficiency is:
    • E = TRANSF/Ts
    • This occurs with the probability (1-p)*(1-q)
  • Case 2: Efficiency in transmitting an error packet The delivery of an error packet takes place with the probability: r = p + (1-p)*q The average packet delay in ARQ scheme is D = TS + TIMEOUT(p/(1-p)) In this case efficiency is: E = TRANSF/D
  • ADVANTAGES
    • Simple to implement.
    • Frames numbering is modulo-2 i.e, only 1 bit is required.
    • Can be used for noisy channels.
    • Has both error and flow control mechanism.
    • Has timer implementation.
  • DISADVANTAGES
    • When propagation delay is long, it is extremely inefficient.
    • Only one frame is sent at a time.
    • Timer should be set for each individual frame.
    • No pipelining.
    • Sender window size is 1( disadvantage over Go back n ARQ).
    • Receiver window size is 1( disadvantage over selective repeat ARQ).
  • APPLICATIONS
    • IBM Binary Synchronous Communications protocol (Bisync): character-oriented protocol
    • XModem : modem file transfer protocol
    • Trivial File Transfer Protocol : simple protocol for file transfer over UDP
    • THANK YOU