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Analyzing the effect of timer timeout and packet length on the performance of error control protocols

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International Journal of Emerging Trends & Technology in Computer Science (IJETTCS) is an online Journal in English published bimonthly for scientists, Engineers and Research Scholars involved in computer science, Information Technology and its applications to publish high quality and refereed papers. Papers reporting original research and innovative applications from all parts of the world are welcome. Papers for publication in the IJETTCS are selected through rigid peer review to ensure originality, timeliness, relevance and readability. The aim of IJETTCS is to publish peer reviewed research and review articles in rapidly developing field of computer science engineering and technology. This journal is an online journal having full access to the research and review paper. The journal also seeks clearly written survey and review articles from experts in the field, to promote intuitive understanding of the state-of-the-art and application trends. The journal aims to cover the latest outstanding developments in the field of Computer Science and engineering Technology.

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									    International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
       Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 1, Issue 2, July – August 2012                                          ISSN 2278-6856




       Analyzing the effect of timer timeout and
       packet length on the performance of error
                   control protocols
                                            Shashi Kumar D1, Nagamani A2
                                            1
                                            Christ University, Faculty of Engineering,
                                                 Kaniminike, Bangalore-56, India
                                        2
                                          Dept. of Electronics and Communication Engineering,
                                                     Bhaskar Engineering College,
                                                         Hyderabad, India

Abstract: In the present day computer networks quality of         consider the Stop-And-Wait protocol because it is known
service is a major issue, which invariably depends on the         to perform poorly [1].
network performance under various network constraints such        In both cases, an error is detected at the sender by either a
as flow control, error control, bandwidth, data traffic, buffer   timer interrupt or a NACK from the receiver. At this
handling etc. In this paper we are Analyzing the Effect of        point, if the sender backs up to the first packet in error,
Timer timeout and Packet length on the performance of error
                                                                  i.e., the first packet that is not yet ACKed, and restarts
control protocols and conclusions are drawn
                                                                  the transmission, the strategy is referred to as Go-Back-N
Keywords: Quality of Service, Go-Back-N ARQ, Selective
                                                                  [2].
Repeat ARQ, Timer Timeout, Packet Length, Throughput

1. INTRODUCTION
In computer networks, mostly we come across three types
of errors.

     Lost frames
     Lost Acknowledgements
     Delayed Acknowledgements

Most Error Control techniques are based on either Error
Detection Scheme (e.g., Parity checks, CRC), or
Retransmission Scheme. Error control schemes that                      Figure 1: Go-Back-N ARQ with lost frame [2]
involve error detection and retransmission of lost or
corrupted frames are referred to as Automatic Repeat              If, on the other hand, the sender retransmits only those
Request (ARQ) error control.                                      packets which are in error, the strategy is called selective-
Error control protocols, as the name implies, these               repeat. Fig. 1, Fig. 2.and Fig. 3 shows the flow diagrams
protocols are used to recover from errors. When some              of       Go-Back-N         and       Selective        Repeat
user submits a message to the network to be transmitted           ARQ’s.
to another user, the message is usually split into packets
which are transmitted over the network and reassembled
at the other end.
A packet in transit encounters one or more channels,
(e.g., satellite, copper wire or optical fiber), and nodes (or
routers), which route the packet to the destination. These
intermediate elements can induce errors in the packet in
that either the packet could get garbled, or dropped
altogether. The former is usually due to random electrical
noise in the channels while the latter is due to buffer
overruns at the nodes and is caused by contention for
resources, a phenomenon often referred to as congestion.
Two error control protocols that we are primarily
interested in analysis are the Go-Back-N and the
Selective Repeat protocols. We shall however not
                                                                   Figure 2 Go-Back-N ARQ with lost Acknowledgement
                                                                                         [2]
Volume 1, Issue 2 July-August 2012                                                                                  Page 190
   International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
       Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 1, Issue 2, July – August 2012                                          ISSN 2278-6856


                                                                      (Timer Timeout vs. Throughput)


                                                                          Tout
                                                              SL/No                     Ps           X
                                                                          (ms)
                                                                           0                         0
                                                                1                        0
                                                                          1250                   0.0367
                                                                2                       11
                                                                          1500                   0.3267
                                                                3                       98
                                                                          1750                   0.5367
                                                                4                       161
Figure 3: Selective Repeat ARQ with lost frame [2]
                                                                          2000                   0.6733
                                                                5                       202
2. SIMULATIONS AND RESULTS
                                                                          2250                   0.6767
                                                                6                       203
The analysis on the performance of error control                          2500                      0.68
protocols, such as Go-Back-N ARQ and Selective Repeat           7                       204
ARQ is done by conducting experiments using                               2750                      0.68
BENCHMARK LAN TRAINER KIT and the simulation                    8                       204
software.                                                                 3000                   0.6867
                                                                9                       206
  2.1 Setting the configuration menu

In both, the sender and receiver machines the following
values needed to be entered in the configuration windows.
After calculating the timer timeout values for various data
rates experiments are conducted for constant
experimental duration. Then the values of successful
transmission are noted for different timer timeout values
and packet lengths.

      TABLE 1: Configuration windows at sender and
                       receiver


                 PC 1                        PC 2
     Node Id             0        Node Id            0         Figure 4: Timer Timeout Vs. Throughput
     Protocol      CSMA/C        Protocol      CSMA/C
                       D                           D
     Baud rate     8Kbps (at     Baud Rate     8Kbps (at       TABLE 3: Results for Go-Back-N ARQ
                    both the                    both the          (Packet length Vs. Throughput)
                     config                      config
                   menu and                    menu and
                     NEU)                        NEU)                   Pl in
                                                              SL/No                Ps           X
     Duration         100s       Duration        100s                   Bytes
      Packet       1000 bytes     Packet       1000 bytes
      length                      Length                        1         0        0            0
       Inter            400 ms     Inter            400 ms
      Packet                      Packet                        2        500      314         0.5233
      Delay                       Delay
     Direction          Sender   Direction      Receiver        3        750      250         0.6250

A. Go-Back-N ARQ                                                4       1000      199         0.6633
           TABLE 2: Results for Go-Back-N ARQ                   5       1250       0            0

Volume 1, Issue 2 July-August 2012                                                                     Page 191
   International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
       Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 1, Issue 2, July – August 2012                                          ISSN 2278-6856




        Figure 5: Packet length Vs. Throughput

B. Selective Repeat ARQ
                                                              Figure 6: Timer Timeout Vs. Throughput
       TABLE 4: Results for Selective Repeat ARQ
           (Timer Timeout Vs. Throughput)                     TABLE 5: Results for Selective Repeat ARQ
                                                                 (Packet length Vs. Throughput)

     SL/No    Tout
              (ms)
                          Ps            X              SL/No          Pl in
                                                                                     Ps           X
                                                                      Bytes
       1        0          0                     0
                                                          1              0            0           0
       2      1250        88              0.2933
                                                          2            500          298        0.4967
       3      1500        128             0.4267
                                                          3            750          229        0.5725
       4      1750        187             0.6233

       5      2000        187             0.6233          4            1000         191        0.6367

       6      2250        204               0.68          5            1250           0           0

        7     2500        199             0.6732

       8      2750        195               0.65

       9      3000        193             0.6433




                                                              Figure 7: Packet length Vs. Throughput

                                                     C. Comparison of Go-Back-N ARQ & Selective Repeat
                                                     ARQ


Volume 1, Issue 2 July-August 2012                                                                Page 192
   International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
       Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 1, Issue 2, July – August 2012                                          ISSN 2278-6856


                                                               with Go-Back-N protocol for a given packet length. In the
                                                               other hand Go-Back-N ARQ will give better throughput
                                                               for lower values of Packet length than compared to the
                                                               Selective Repeat ARQ.

                                                               4. FORMULA USED

                                                               Formula used to calculate throughput is.




        Figure 8: Timer Timeout Vs. Throughput                 Where
                                                               X = Throughput
                                                               Ps =Successfully Transmitted packets
                                                               Pl= Packet Length in Bytes
                                                               De=Duration of Experiment in seconds
                                                               Dr=Data rate in Kbps
                                                               Tout= Timer Timeout value in seconds

                                                               5. CONCLUSION AND FUTURE WORK
                                                               In this paper we made an analysis of the effect of timer
                                                               timeout values and packet length on throughput of data
                                                               link layer error control protocols, conducting experiments
                                                               using BENCH MARK LAN TRAINER KIT and
                                                               simulation software without considering the bit errors.
                                                               Further enhancement can be made to analyze the effect of
                                                               timer timeout and packet length on the throughput of the
        Figure 9: Packet length Vs. Throughput
                                                               system considering bit errors. Also we can analyze the
                                                               effect of data rate on throughput.
3. RESULT ANALYSIS
The simulation results are obtained for Go-Back-N ARQ          References
and Selective Repeat ARQ by varying packet length and
Timer timeout values, using BENCHMARK LAN                      [1] Zwaenepoel, W., “Protocols for Large Data Transfers
TRAINER KIT and the simulation software.                           on Local Networks”, Proc. of the ACM Sigcomm, pp
Fig. 4 and Fig. 6 show the plots of Timer timeout Vs.              22-32, 1985
Throughput for Go-Back-N ARQ and Selective Repeat              [2] Tanenbaum, A.S., Computer Networks, Prentice-
ARQ. In this experiment, the value of packet length,               Hall Inc.,Englewood Cliffs, NJ 07632, 1981
1000Bytes and duration of the experiment, 300 seconds is       [3] S. Lin, D. J. Costello, Jr., and M. J. Miller,
taken for the simulation. From plots it is clear that as we        “Automatic-repeat-requesterror-control     scheme,”
increase the timer timeout, the throughput of the system           IEEE Commun., vol. 22, pp. 5-17, Dec. 1984
is increasing up to certain level and then it is almost same   [4] M. Moeneclaey, H. Bruneel, I. Bruyland, and D. Y.
for all other values. For the current scenario, the                Chung, “Throughput optimization for a generalized
throughput is increasing up to the timeout value of 2250;          stop-and-wait ARQ scheme, ”IEEE Trans.Commun.,
thereafter it is almost equal for all other values.                vol. COM-34, pp. 205-207, Feb. 1986
Fig. 5 and Fig. 7 show the plots of Packet length Vs.          [5] Anagnostou, M.E. and E.N. Protonotarios,
Throughput for Go-Back-N ARQ and Selective Repeat                  "Performance analysis of the selective repeat ARQ
ARQ. From plots it is very clear that the throughput of            protocol," IEEE Trans.Commun., vol. COM-34, pp.
the system will increase up to certain range of packet             127-135, Feb. 1986.
lengths then it returns back to zero and continuous to be      AUTHOR
in zero for further increase in the packet length.
                                                                               Shashi Kumar D received the B.E degree
Fig. 8 and Fig.9 gives us the comparison results of Go-
                                                                               from SJC Institute of Technology in 2007 and
Back-N ARQ and Selective Repeat ARQ protocols for                              MTech degree in Electrical Engineering from
Timer timeout Vs. Throughput and Packet length Vs.                             Indian Institute of Technology Madras in
Throughput respectively. From these plots we can infer                         2010. During June, 2010- July, 2011, he
that for lesser timer timeout values we will get more                          stayed in ICFAI University Dehradun as a
throughput in case of Selective Repeat when compared
Volume 1, Issue 2 July-August 2012                                                                             Page 193
    International Journal of Emerging Trends & Technology in Computer Science (IJETTCS)
       Web Site: www.ijettcs.org Email: editor@ijettcs.org, editorijettcs@gmail.com
Volume 1, Issue 2, July – August 2012                                          ISSN 2278-6856


Faculty member, from July-2011 to till date working as
Assistant Professor in Christ University, Faculty of Engineering.

                Nagamani A received the B.Tech from
                Bhojreddy College of Engineering &
                Technology for women in 2004, MTech degree
                in Electrical Engineering from Indian Institute
                of Technology Madras in 2010, From August
2010 to till date working as Assistant Professor in Bhaskar
Engineering College (JB group of institutions).




Volume 1, Issue 2 July-August 2012                                                  Page 194

								
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