Group B Ppt

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

Group B Ppt

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Group B Ppt