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					                                                                              International Journal of Computer Information Systems,
                                                                                                                  Vol. 3, No. 2, 2011

   Quantitative Analysis of DSDV Routing Algorithm
             for Carrying Packet Telephony
                           P.K.Suri                                                         Sandeep Maan
    Professor & Head, Deptt. of Computer Sc & Appl,                                    Assistant Professor,
        Kurukshtra University, Kurukshtra, India                         Government Post Graduate College, Gurgaon, India
              Email: pksuritf25@yahoo.com                                      Email: sandeep.mann23@gmail.com



Abstract— Problem of implementing Packet Telephony over                 call, whole path from caller to callee is reserved (copper
Mobile Ad-hoc Networks has been eluding research fraternity             path). The call routes are dedicated and no one else can use
due to the peculiar characteristics of these networks including         this path while the communication is going on. This strategy
dynamic nature of nodes. The nodes keep on changing their               though ensures quality but also leads to wastage of
location and hence re-routing is frequently required. So a              resources. Other solution to the problem of telephony is
robust routing algorithm is prerequisite for successful
implementation of Packet Telephony over Mobile Ad-hoc
                                                                        Packet Telephony where no copper path is reserved and the
Networks. In this work authors are trying to evaluate DSDV              conversations are moved in form of IP packets from caller to
routing algorithm in order to ascertain feasibility of successful       callee.
implementation of Packet Telephony over Mobile Ad-hoc                      In Packet Telephony [1], telephonic conversations are
Networks.                                                               transported in form of IP packets and different packets may
                                                                        follow different path to the destination. Extension of the
                                                                        concept of VoIP in Mobile Ad-hoc Networks can be highly
Keywords- Mobile Ad-hoc Network; DSDV; Packet                           beneficial. It would help in cost-free extension of existing
Telephony; Voice over Internet Protocol; Network                        fixed telephony and may help in setting up of Wireless
Architecture; Packet Delivery Ratio; End-to-End delay; Jitter.
                                                                        Intercom where all nodes in the area are free to roam around.


                      I.    INTRODUCTION                                                   II. QUALITY OF SERVICE
   Mobile Ad-hoc Networks or MANETs are the latest                         Successful implementation of Packet Telephony over
addition to the family of Wireless Networks. In MANETs, a               Mobile Ad-hoc Networks [2] is constrained by a number of
number of autonomous and mobile nodes communicate with                  service related parameters termed as QoS parameters, as
each other by forming multi-hop networks and maintaining                defined by International Telecommunication Union (ITU).
connectivity in decentralized manner.                                   QoS parameters related to the Packet Telephony can be
   Every node can move freely within the premises of the                classified into two categories viz. Call Level Parameters and
network. Hence the topology in a MANET keeps on                         Packet Level Parameters. Various packet level parameters
changing.                                                               include Packet Drop Rate, End-to-End delay, Jitter,
   Each node, participating in a MANET, acts as a potential             throughput etc. Some QoS parameters are very critical and
router and the system lacks a centralized routing system.               their value must remain in specified range for successful
Every other node within the range of a given node is termed             implementation of Packet Telephony. While for other
as neighbour. Two neighbours communicate directly. For                  parameters there may be no range limitation but the
communication with some distant node, in the network,                   qualitative performance in terms of these parameters is
individual node(s) rely on the neighbours. A node needs to              important to realize packet telephony over the mobile ad-
maintain and update route to every other node in the                    hoc networks. Various QoS parameters with their specified
network so that it can forward the packets toward its                   range for successful implementation of packet telephony
(packet‘s) destination. The whole idea of MANETs is based               over mobile ad-hoc networks are listed in table 1.
on the assumption of cooperation between various
participating nodes. The dynamic nature of nodes and open
wireless channel make MANETs vulnerable to security                                    III. NETWORK ARCHITECTURE
threats.                                                                   Network architecture for implementation of Packet
   Data in computer networks can be transmitted through                 Telephony over Mobile Ad-hoc Networks is outlined in
three underlying techniques in circuit switching, message               figure 1. At application layer corresponding voice data is
switching, and packet switching. Conventional telephonic
network are circuit switched where, before initialization of a




       August Issue                                          Page 29 of 107                                   ISSN 2229 5208
                                                                             International Journal of Computer Information Systems,
                                                                                                                   Vol. 3, No. 2, 2011
       TABLE I.            QOS VALUES FOR PACKET TELEPHONY                 The routing packets are broadcast and contain the address
                                                                        of destination. The recentness of a route, in the table, is
        Critical QoS Parameter           Acceptable Range               identified by its sequence number. If two routing updates
                                                                        have same sequence number then one with lesser number of
                                                                        hops is preferred. New routes discovered by a node are
                                                                        further advertised by various nodes with routing information.
              E2E Delay                      <= 120ms
                                                                        The performance of DSDV is highly dependent upon the
                                                                        time duration between route updates. Routes that are broken
                                                                        due to the dynamics of network are reported by the MAC
                  Jitter                     <= 40ms
                                                                        layer and communicated to the network layer where the hop
                                                                        count is replaced with infinity for representing broken link.

          Packet Delivery Rate                >= 95%



produced which is encoded and compressed then forwarded
towards the transport layer. One application layer solution
for packet telephony over Mobile Ad-hoc Networks is
G .729 [3] codec. Transport layer is responsible for end-to-
end delivery of compressed voice from caller to callee. One
common transport layer solution for packet telephony over
Mobile Ad-hoc Networks is RTP/UDP [4]. Network layer is
central to the success of the system. Major responsibilities
with the network layer are Packetization and routing. The
compressed voice coming from transport layer is packetized
as IP packets for routing towards destination. A number of
routing protocols [5] are available out of these most
common ones are DSR, DSDV, TORA and AODV. In this
work a system architecture based on DSDV routing protocol
is evaluated. It would be ascertained whether or not some
network architecture in lines with this work and employing
DSDV routing protocol can be used for successful
implementation of Packet Telephony over Mobile Ad-hoc
Networks. The role of data link layer is medium control and                       FIGURE 1: PROPOSED NETWORK ARCHITECTURE
hiding the details of channel from the upper layers. Physical
layer is responsible for moving the voice data. IEEE
802.11g [6] provides pretty popular specifications for both                As an example, the route discovery broadcast packets in
Physical and Data Link Layers. A number of devices                      DSDV may move as represented in figure 2. The
working on these specifications are available in market. So,            corresponding routing table maintained by the source node
authors propose to use these specifications.                            ‗s‘ may be like figure 3.
                                                                           DSDV as a routing algorithm can be quite suitable in
                                                                        Mobile Ad-hoc Networks with small number of nodes. Due
              IV. DSDV ROUTING ALGORITHM                                to predetermined routes, delays in routing first packets
                                                                        would be minimal (in case of DSDV). This is one of the
   DSDV [7] is a table driven algorithm designed by
                                                                        oldest routing algorithms that provided loop free routing
C.Perkins and P. Bhagwat]. In this Bellman-Ford algorithm
                                                                        solution.
is employed. It is a proactive routing algorithm where each
                                                                           Due to frequent route discovery in won‘t allow nodes to
node maintains its copy of routing table. Each record in the
                                                                        go in sleep mode for saving energy thereby it is harsh on
table contains details of some node in the network with
                                                                        battery. It consumes a lot of bandwidth due to frequent
number of hops and next neighbour address to reach that.
                                                                        routing activities. It is not suitable for larger networks.
Each record has a sequence number to identify the
                                                                           Full network architecture, discussed above, with DSDV,
recentness of the route. Routing tables are regularly updated
                                                                        as routing algorithm was implemented in ns2 (Network
through periodic transfer of routing information in the
                                                                        Siumator-2) [8-10] and following observations were made.
network. These results in large traffic in the network, to
decrease the amount of traffic two type of packets are used
viz. full dump (containing whole routing information) and
incremental (Carrying only changes in last information).




      August Issue                                           Page 30 of 107                                  ISSN 2229 5208
                                                                          International Journal of Computer Information Systems,
                                                                                                              Vol. 3, No. 2, 2011
                          4
                  A                B           5
          2                                                                         Routing Table at Node „S‟ (Figure 2)



      S                                                                     Destination   Next   Distance   No of     Sequence
                                                   D                                      Hop               Hops      Number

                              5                                                 A          A        2        0          A 25
          3       E                    C
                                               4
                                                                                B          A        6        1          B 21


              FIGURE 2: DSDV ROUTE DISCOVERY                                    C          E        8        1          C 22


                                                                                D          A       11        2          D 20
            V. PACKET DELIVERY RATE (RATIO)
   PDR is one of the most important parameter for deciding
on viability of telephony service. In layman terms it                           E          E        3        0          E 24
signifies the amount of telephonic conversation that is
successfully transferred from caller to receiver. It is
important in calculating the Packet Loss Rate, representing                    FIGURE 3: ROUTING TABLE IN DSDV
packets that are lost in the network and are never delivered
at the destination. This would represent loss of voice and
hence communication. In this literature we refer packet loss        2) Same sort of behaviour was expressed by the curves for
rate according to the following relation:                              simultaneous RTP/UDP & FTP/TCP transfers except for
   (Packet Loss Rate) = 100 – (Packet Delivery Ratio)                  the fact that it attains unacceptable PDR values for
   A PDR of above 95% is prerequisite for successful                   smaller network size.
implementation of packet telephony. PDR is calculated as            3) With increase in number of connections PDR drops and
per equation:                                                          becomes unacceptable if number of connections is more
                                                                       than 05 (in case of telephonic traffic only). Moreover in
                                                                       case of simultaneous voice and data traffic the
                                                                       performance degrades even more sharply and become
                                                                       unacceptable when number of active connections is
                                                                       more than 1.
                                                                    4) With increase in number of nodes the network actually
                                                                       performance better but PDR is never in acceptable range.
   The network architecture was simulated using ns2 with
                                                                    5) PDR increases with increase in velocity. Initially with
two types of data in the network. One voice data based on
                                                                       increase in velocity network performance is raised but at
RTP/UDP while other type of data was due to a FTP
                                                                       higher speeds it degrades somewhat.
transfer (i.e. FTP/TCP) ported with TCP.
                                                                    6) In case of both voice and data traffic network is not able
                                                                       to provide requisite PDR.
   Performance of the proposed architecture with respect to
important network characteristics, viz. network area,
number of nodes, number of simultaneous telephonic calls,
maximum node speed are plotted in figure 4. In every plot           B. Explanation:
all other network characteristic parameters except for one          1) With increase in network size keeping number of users
are kept constant.                                                     (nodes) constant effective user density decreases and
                                                                       hence decreases number of probable routers per unit area
A. Observation(s)                                                      thus the performance of network degrades with size.
                                                                    2) Adding a TCP connection adds extra load on the
1) It was observed that with increase in network size (other           networks and hence routers. Moreover TCP is a
   parameters being constant) Packet Delivery Ratio (Rate)             connection oriented reliable network protocol thereby
   decreases and becomes unacceptable for larger network               using more control packets and hence injecting large
   size.                                                               data into the network and hence performance degrades.




      August Issue                                       Page 31 of 107                                          ISSN 2229 5208
                                                                        International Journal of Computer Information Systems,
                                                                                                            Vol. 3, No. 2, 2011
3) Increasing number of connections means additional                3) With increase in number of nodes E2E initially
   telephonic traffic and hence PDR decreases.                         decreases afterwards it increases a bit with number of
4) DSDV is a proactive routing algorithm where routes are              nodes.
   predefined and large number of nodes would mean                  4) With increase in maximum speed of nodes E2E increase
   higher network activities and hence large control data.             if node speed is too high.
   With increase in number of nodes the user density
   increases thereby increasing probable routers and hence          B. Explanation
   chances of route failure decreases. But with higher              1) With increase in network size keeping number of
   number of nodes control packets grow and thus larger                users/nodes constant, effective user density decreases
   queues at router would mean decrease in PDR.                        and hence decreases number of probable routers per unit
5) As far as effect of node speed on Packet Delivery Rate is           area thus the E2E increases.
   concerned, with medium speed increasing the number of            2) DSDV is a proactive routing algorithm and E2E delay is
   nodes actually supports connectivity as the routers are             measured for those packets which are successfully
   changing their locations frequently and hence chances of            delivered and being proactive algorithm DSDV nodes
   finding router in vicinity increases overcoming factor              have in-hand (readymade) information on routes in its
   like increased dynamicity of network leading to higher              table. Thereby the E2E delay is small but with large
   PDR at lower speeds but with speed becoming high later              number of connection chances of availability of in-hand
   factor start dominating leading to dip in PDR curve at              routing information decreases thereby an increase in
   higher speed.                                                       E2E delay.
                                                                    3) Again in DSDV (proactive) most of the routes are
                                                                       predetermined which requires continues routing activity
                                                                       inspite of the fact that routes may be not required at all.
          VI. END TO END DELAY (E2E DELAY)                             This means large number of nodes would mean higher
                                                                       network activities and hence large control data. Whereas
   It is observed that for DSDV based proposed network                 with increase in number of nodes the user density
architecture it is not possible to meet QoS requirements. In           increases thereby increasing probable routers and hence
this section only traffic from voice conversations in                  chances of route failure decreases. Due to these
considered and further evaluation of the network                       conflicting factors increase in E2E delay due to increase
architecture in terms of End to End (E2E) delay is done.               in number of nodes is not that pronounced as in case of
   An E2E delay below 120ms is prerequisite for successful             on-demand routing algorithms like DSR or AODV.
implementation of packet telephony (as per ITU-T
recommendations).                                                   4) To retreat the relation between speed and E2E delay is
                                                                       affected by two factors viz.
   The first delay comes in form of delay taken by the G.729
codec in processing a 10ms fame which is 15ms. If E2E                     1) At lower speeds, increasing the number of nodes
delay is more than 120 ms then the telephony system more                     actually supports connectivity as the chances of
or less becomes half duplex and the system performance is                    finding router in vicinity increases.
unacceptable, This would result in quality degradation of                 2) But at higher speed large dynamicity (frequent
voice and hence communication. In this literature we refer                   reconfiguration) increases and hence routes keep on
packet loss rate according to the following relation:                        changing. In DSDV being a proactive routing
                                                                             algorithm this factor should hamper the network
E2E Delay = Accumulation Delay + Packetization Delay +                       performance greatly. That is why at higher speeds
Network Delay                                                                an increase in E2E delay was observed.


   Performance of the proposed architecture with respect to                                 VII.    JITTER
important network characteristics, viz. network area,                  Jitter signifies the amount of time between successive
number of nodes, number of simultaneous telephonic calls,           packets received at destination. If Jitter is more than 40 ms
maximum node speed are plotted in figure 5. In every plot           then the speech received at receiver end would not be true
all other network characteristic parameters except for one          replica of the speech exiting speaker‘s mouth and there
are kept constant.                                                  would be abrupt silence in the reproduced speech. This
                                                                    would result in quality degradation of voice and hence
A. Observation(s)                                                   communication. In this literature we refer packet loss rate
1) It was observed that with increase in network size (other        according to the following relation:
   parameters being constant) E2E increases.
2) With increase in number of connections there is an                  Jitter = Arrival time of nth packet – Arrival time of (n-
   increase in value of E2E delay.                                  1)th packet




      August Issue                                       Page 32 of 107                                   ISSN 2229 5208
                                                                         International Journal of Computer Information Systems,
                                                                                                             Vol. 3, No. 2, 2011




                           FIGURE 4:    STUDY OF PACKET DELIVERY RATIO WITH VARIOUS NETWORK CHARACTERISTICS




                                                                    A. Observation:
   A Jitter below 40ms is prerequisite for successful               1) From DSDV curve for Jitter it was observed that with
implementation of packet telephony (as per ITU-T                       increase in network size (other parameters being
recommendations).                                                      constant) Jitter increases.
                                                                    2) With increase in number of connections Jitter increases.
    “Jitter represents unpredictability of E2E delay as it          3) With increase in number of nodes, Jitter initially
is measure of variation in E2E delay”                                  decreases afterwards its increases a bit with number of
   In the following section simulation results in graphical            nodes.
form are presented and hence the performance of DSDV in             4) If speed of nodes is high then Jitter increases.
terms of Jitter under different network parameters as
depicted in figure 6.




      August Issue                                      Page 33 of 107                                        ISSN 2229 5208
                                                                         International Journal of Computer Information Systems,
                                                                                                             Vol. 3, No. 2, 2011




                             FIGURE 5:    STUDY OF END-TO-END DELAY WITH VARIOUS NETWORK CHARACTERISTICS




B. Explanation:                                                        activities and hence large control data. Whereas with
1) As already explained with increase in network size                  increase in number of nodes the user density increases
   keeping number of users/nodes constant effective user               thereby increasing probable routers and hence chances
   density decreases and hence decreases number of                     of route failure decreases. Due to these conflicting
   probable routers per unit area thus the performance of              factors change in Jitter due to increase in number of
   network degrades with size.                                         nodes (with smaller number) is not that pronounced as in
2) Again, DSDV is a proactive routing algorithm and Jitter             case of on-demand routing algorithms like DSR or
   is measured for those packets which are successfully                AODV.
   delivered and being proactive algorithm DSDV nodes               4) To retreat the relation between speed and Jitter is
   have in-hand (readymade) information on routes in its               affected by two factors viz.
   table. Thereby the Jitter is small but with large number            a.    At lower speeds, increasing the number of nodes
   of connection chances of availability of in-hand routing                  actually supports connectivity as the chances of
   information decreases thereby an increase in Jitter on                    finding router in vicinity increases.
   extreme right hand side of the curve was observed.
3) Again as in DSDV most of routes are predefined and
   large number of nodes would mean higher network




      August Issue                                      Page 34 of 107                                     ISSN 2229 5208
                                                                            International Journal of Computer Information Systems,
                                                                                                                Vol. 3, No. 2, 2011




                                   FIGURE 6:     STUDY OF JITTER WITH VARIOUS NETWORK CHARACTERISTICS




   b.    But at higher speed large dynamicity also means
         frequent configuration and hence route change. In                                         REFERENCES
         DSDV being a proactive routing algorithm this
         factor should hamper the network performance                 [1]   Jori Liesenborgs, ―Voice over IP in networked virtual Environments‖,
         greatly. That is why at higher speeds an increase in               PhD Thesis, University of Maastricht, 1999-2000, pp. 30-40.
                                                                      [2]   Paolo Giacomazzi et al., ―Quality of Service for Packet Telephony
         Jitter was observed.                                               over Mobile Ad Hoc Network‖, IEEE Network, Jan/Feb 2006.
                                                                      [3]   M. E. Perkins et al., ―Characterizing the Subjective Performance of
                                                                            the ITU-T 8 kb/s Speech Coding Algorithm ITU-T G.729,‖ IEEE
                  VIII.  CONCLUSIONS:                                       Commun. Mag., vol. 35, no. 9, Sep. 1997 pp. 74–81.
                                                                      [4]   Juhana Mattila, ―Real-Time Transport Protocol‖, Oct 2003.
From the study of network architecture with DSDV as                   [5]   E. M. Royer and C.-K. Toh. ―A Review of Current Routing Protocols
routing algorithm it was found that successful                              for Ad Hoc Mobile Wireless Networks,‖ IEEE Pers. Commun., vol. 6,
implementation of packet telephony over a mobile ad-hoc                     no. 2, Apr. 1999.
                                                                      [6]    ―Information Technology—Telecommunications and Information
network is not feasible.                                                    Exchange Between Systems — Local and Metropolitan Area
                                                                            Networks- Specific Requirements — Part 11: Wireless LAN Medium




        August Issue                                     Page 35 of 107                                            ISSN 2229 5208
                                                                                 International Journal of Computer Information Systems,
                                                                                                                     Vol. 3, No. 2, 2011
     Access Control (MAC) and Physical Layer (PHY) Specifications‖,                                 AUTHORS PROFILE
     IEEE Std 802.11-1997.
[7] C.E. Perkins and P. Bhagwat, ―Highly Dynamic Destination-
                                                                           Dr. P.K.Suri (pksuritf25@yahoo.com) has been working in the
     Sequenced Distance-Vector Routing (DSDV) for Mobile Computers,‖
                                                                           department of Computer Science and Applications, Kurukshetra University,
     Proc. SIGCOMM ‘94 Conf. Communications Architectures,
                                                                           Kurukshetra, India for more than twenty five years. He has guided a
     Protocols and Applications, ACM Press, 1994, pp. 234–244.
                                                                           number of PhD students. His areas of specialization includes Computer
[8] P.K. Suri and Sandeep Maan, ―Simulation of Packet Telephony in
                                                                           based simulation and modeling, Computer Networks etc. Presently he is
     Mobile Ad-hoc Networks Using Network Simulator‖, International        acting as Dean Faculty of Science in the university.
     Journal of Advanced Computer Science and Applications(IJACSA),
     Vol 2, No 1 , January 2011, pp 87-92.
[9] P.K. Suri and Sandeep Maan, ―A Study of Simulation Tool(s) for         Sandeep Maan (sandeep.mann23@gmail.com) is presently working as
     Mobile Ad-Hoc Networks‖, International Journal of Advanced            Assistant Professor in Computer Science at Govt. Post Graduate College,
     Research in Computer Science, Volume 2, No. 4, July-August 2011       Sector-14, Gurgaon, India. He completed his M.Tech in Computer Science
[10] P.K. Suri and Sandeep Maan, ―Traffic Simulation for Packet            and Engineering from Kurukshetra University Kurukshetra. He is presently
     Telephony in Mobile Ad-hoc Networks‖, International Journal of        pursuing his PhD in Computer Science from Department of Computer
     Computer Science and Technology(IJCST), Vol 2, Issue 1 , March        Sceince and Applications,Kurukshetra University, Kurukshetra. His areas
     2011, pp 123-127.                                                     of intereset includes Mobile Adhoc Networks, System Simulations and
                                                                           Atrtificial Intelligence.




       August Issue                                             Page 36 of 107                                         ISSN 2229 5208

				
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