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  • 8/15/2019 Simulation of IPv4-to-IPv6 Dual Stack Transition Mechanism (DSTM) between IPv4 Hosts in Integrated IPv6/IPv4 Ne…

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    2009 International Conference on Computers and Devices for Communication ACN

    978-81-8465-152-2/09/$26.00©2009 CODEC

    Simulation of IPv4-to-IPv6 Dual Stack TransitionMechanism (DSTM) between IPv4 Hosts in

    Integrated IPv6/IPv4 Network Krishna Chakraborty, Nitul Dutta, S R Biradar

     Abstract -IPv6 offers variety of enhancements including increased

    addressing capacity, Quality of Service (QoS) provisioning, built

    in security through IPSec and improved routing efficiency, over

    IPv4. But moving from the current version of IPv4 to the future

    version of IPv6 is not a straightforward process due to their

    incompatibility and will consume significant amount of time. So

    for the coming years both the protocols need to coexist. For the

    smooth interoperation of the two protocols, various well defined

    transition mechanisms have been proposed so far. In this paper

    a comparative study of the behavior of IPv4-only network withthat of Dual Stack Transition Mechanism (DSTM) under various

    types of traffic patterns is carried out. In the proposed DSTM

    enabled network architecture, the hosts in IPv4 network initiates

    connection with hosts in the IPv4 network over an integrated

    IPv4/IPv6 network. The performance metric considered in this

    work is mean end-to-end delay for both the scenarios.

    Assessment of the mean end-to-end delay is performed on

    various applications like Real Audio (RA) and CBR over UDP

    and FTP over TCP. All the simulations are performed using

    Network Simulator 2 (ns-2). 

    I.  I NTRODUCTION

    THE present version of the Internet Protocol, IP version 4(IPv4), has various limitations that are being focused as theInternet continues its phenomenal growth and expansion ofservices. The most familiar problem with IPv4 is its limitedaddress space, which is based on a 32-bit address and aninefficient address allocation mechanism. However there areseveral other shortcomings such as its ‘best-effort’ deliverymechanism, lack of support for Quality of Service (QoS) andmobility issues, and the manner in which security is handled.All of them have contributed towards the requirement for animproved Internet protocol. Besides, most applications todaysupport IPv4; thus there is a need for these applications to beaccessible on IPv6 network. All these issues have been

    resolved in IPv6 by expanding the address space, which is based on a 128-bit address, introducing Quality of Service(QoS), and also improving built-in security using IP Security(IPSec) [1].

    Rapid mushrooming of the Internet and of the number of

    Sikkim Manipal Institute of Technology,Computer Sc. & Engg. Deptt.,East Sikkim, Sikkim, India. Email: [email protected] 

    IPv4 users contributes to the fact that the transition from IPv4to IPv6 is expected to be a long process. The key to asuccessful transition to IPv6 is compatibility with the largeinstalled base of IPv4 hosts and routers. Maintainingcompatibility with IPv4 during the exploitation of IPv6 willrationalize the job of transitioning the Internet to IPv6. Thisspecification defines a set of mechanisms that IPv6 hosts androuters may implement in order to be compatible with IPv4

    hosts and routers. But IPv6 lacks backward compatibility withIPv4, leading to the fact that IPv6 hosts and routers will not beable to deal directly with IPv4 traffic and vice-versa. Also, itis impractical to invest in a fully new IPv6 infrastructure. Thisis due to the fact that most of the applications that exist todaywere written for IPv4 network and moreover the largeinfrastructures where a huge amount has been invested insetting the IPv4 network totally refute from converting toIPv6. A huge cost will be incurred to re-setup the network.Moreover, movement from IPv4 to IPv6 is not a straightaway process and so cannot take place within a fortnight; it requiresdeveloping mechanisms so that IPv4 and IPv6 may existtogether for at least many coming years and during this

    transition period IPv4 network will totally disappear [2]. Theaim of this paper is to examine the behavior of a transitionmechanism that will involve the communication between twoIPv4 hosts over an IPv6 network under various trafficconditions. This will make possible the exchange ofinformation between IPv4-only network hosts through anintegrated IPv6/IPv4 network. And hence we call it DualStack Transition Mechanism (DSTM) as the integratedIPv6/IPv4 network maintains a dual stack of both IPv4 andIPv6. The necessity of reexamining the problem arises as theresearch in this area has not very widely been explored.

    The rest of the paper is organized as follows. Section IIdiscusses the related work in this area along with ourmotivation for this research. Section III illustrates the network

    architecture used in the work. The simulation scenario isdiscussed in section IV and section V shows the results anddiscussions. The paper is concluded in section VI.

    II. R ELATED WORK A ND MOTIVATION

    Many transition mechanisms have been proposed so far andresearch work has been carried as well in all thesemechanisms. Although the research in various transitionmechanisms has not been conducted much, but still many

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     papers discuss the Dual Stack Transition Mechanism (DSTM)in various ways. In paper [3], the authors have adopted theDSTM to study network performance with few types of trafficsources: Voice-over-IPv4, FTP-over-IPv6, and MPEG-4-over-IPv6. The performance is evaluated considering bandwidth,throughput, percentage of dropped packets, and mean end-to-end delay of each traffic flow for both IPv4 and IPv6.Through the simulations performed by using the Network

    Simulator 2 (ns-2), it is shown that when the traffic density ofIPv6 session increases, the bandwidth of IPv6 sessionincreases at the expense of the decrement of the bandwidth ofIPv4 session. On the other hand, the increment of the trafficdensity of IPv4 session does not increase its bandwidth due toits lower priority. In addition, the increment of packet size ofIPv6 traffic results in the increment of a little bit of the meanend-to-end delay, but it is not the case for IPv4 traffic. In [4],the impact of IPv6 transition mechanisms on user applicationis discussed. The experimental results show that though performance overheads are minimal, but translation packetsdegrade some performance. The work compares IPv4 versusIPv6 header overhead and header overhead between transition

    mechanisms and also computes CPU utilization of all thesemechanisms and certain other performance aspects likethroughput and round-trip time for several types of traffic. Itwas intended to empirically analyze impacts on transitionmechanisms compared with IPv4-only and IPv6-only network performance. The work in [5] reviews the implementation ofDSTM over IPv6 test-bed (6iNet) in University UtaraMalaysia (UUM). It clearly shows how DSTM works overthe test-bed. Their findings could also be applied to otherorganizational settings which intend to implement IPv6 in thenetwork interconnection. In [6], the authors have analyzedmore than 600 end-to-end IPv6 paths between about 26 test boxes of RIPE NCC over the past two years, and comparedthe delay and loss performance evolution in IPv6 with theirIPv4 counterparts. They have presented and discussed themeasurement methodology, and provided evidence that IPv6network has a higher delay and loss evolution than IPv4.Finally, based upon their measurements, they have assessedthe perceived quality of three real-life applications: VoIP,Video-over-IP and data communication services based uponTCP. They have found that for VoIP and Video-over-IP, thedifferences in delay and packet loss between IPv4 and IPv6 donot translate to the perceived quality domain but forapplications based upon TCP, the differences in delay and packet loss between IPv4 and IPv6 have a strong impact onthe realized throughput. In [7], they have remarked that mostof the transition mechanisms proposed by IETF Next

    Generation Transition Working Group provide only themechanism to initiate sessions from hosts within the IPv6network to those within the IPv4 network, but do not supportthe initiation from IPv4 hosts to IPv6 ones. In their paper,they have proposed the IPv4-to-IPv6 DSTM (4to6 DSTM)which can operate even in the case that hosts in the IPv4network initiate connections within hosts in the IPv6 network.The work shows the performance of the proposed mechanismin terms of the transmission delay of IPv4 packets from IPv4hosts to a DSTM host, and the response time of DNS querieswith varying the session initiation interval and the connectionduration.

    In all of these papers discussed, not much emphasis has

     been given to the hosts that are in IPv4 network and want to

    communicate over an IPv6 network. Moreover, they havealso not detailed much on the performance comparison of thetraffic with DSTM with the traffic with only either IPv4 orIPv6 network. The motivating force behind this work is thatthere is very little exposure given by researchers to the meanend-to-end delay and its impact on applications of IPv4 toIPv6 transition mechanisms and also to such related work. Soexploring this area with a wide variety of real time and other

    applications on different types of traffic was significant.Besides, we also want to show a comparative performanceevaluation of these applications considering both the transitionmechanism as well as only with either of the IPv4 or IPv6network.

    III.  PROPOSED NETWORK ARCHITECTURE

    In this section, we present the description of the architectureof the simulation environment for our work. The scenariogiven in the Figure 1 depicts a conversation between two IPv4 based nodes over an IPv6 based Network. Assumption ismade that the data exchange is realized by means of DualStack Transition Mechanism (DSTM). The packet flows from

    a source node N0 using IPv4 address, encapsulated in an IPv6capable packet header through a DSTM server (node N1),which is the begin point of a tunnel, Tunnel Start Point (TSP).This packet, whose destination address is an IPv4 compatibleIPv6 address, travels through an IPv6 enabled network. TheIPv6 network is realized as an integrated IPv6/IPv4 networkwhere the border nodes maintain a dual stack of IPv4 andIPv6. All the other nodes in the network through which IPv4 packets are tunneled are IPv6-only enabled nodes. The node N4 is another DSTM server which can be considered as theTunnel End Point (TEP), and this is the point where thedestination node's IPv4 address is maintained. These beginand end points of the tunnel are the border routers whichmaintain both IPv4 and IPv6 stacks.

    Figure 1. Proposed Network Architecture

    This is the reason for having the tunneling of packetsthrough the integrated network so that the utilities of dual-stack are adopted along with tunneling transition mechanism.This will avoid the drawbacks of dual-stack approach and addthe advantages of tunneling as mentioned in [5]. The problemwith dual-stack approach is that in this mechanism, IPv6datagram can be copied into the data field of the IPv4datagram and appropriate address mapping is done [8]. Butsome fields in IPv6 have no counterpart in IPv4 when the IPv6datagram is mapped into IPv4 datagram. When it travelsthrough network and arrive in IPv6 host, the datagram do not

    contain all the fields that were in the original IPv6 datagram

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    sent from source. This will result in dropping the informationin these fields. As an alternative to the dual-stack approach,tunneling as discussed in RFC 2893 was suggested toovercome the drawback in dual-stack approach [5]. Finally,the DSTM server forwards the packet with this IPv4 addressto the IPv4 enabled destination node, N5. Node N5(destination node) sends Hello packet to the DSTM server to broadcast its own address.

    To realize the DSTM, ns-2.26 [9] with MobiWan patch pack[10] is used to create IPv6 based scenario. The utility of the patch pack is that it provides some implemented protocolsthrough which IPv6 based network simulations can be performed. The DSTM scenario will include an IPv4 sourcenode which will send its node ID to a DSTM server, whichconverts it into a hexadecimal address that is the tunnel end point address and tunnels it in an IPv6 network. When itreaches the tunnel end point, it is again converted to acorresponding IPv4 address. This node also maintains thedestination node's IPv4 address. It forwards the packet withthe decapsulated IPv4 address to the destination IPv4 node.

    The IPv4 to IPv6 DSTM network architecture consists of

    two DSTM servers, the DSTM TSP and TEP, and IPv4 hosts.The DSTM TSP encapsulates the IPv4 address of the host andalso maintains the permanent IPv6 address of DSTM TEP.The DSTM TEP is located on the boundary of IPv6 networksand IPv4 hosts, and it tunnels IPv4 packets to destination IPv4hosts. The IPv4 host (i.e. the host within the IPv4 network)attempts to initiate a session with another IPv4 host bysending a DNS query message to the IPv4 DNS server. TheIPv4 DNS server replies with the IPv6 address of the DSTMTEP. With this information, the IPv4 packet is directed to theDSTM TEP on the boundary of IPv6 network and IPv4network. The tunneled packet is directed to the DSTM TEPand the DSTM TEP decapsulates the IPv6 header andforwards it to the IPv4 network. The DSTM server holds themapping between the allocated IPv4 address and the IPv6address of the DSTM TEP in its mapping table and sets thelifetime timer with the value of the amount of the time duringwhich the allocated IPv4 address is considered to be valid.

    IV.  SIMULATION SCENARIO

    The proposed transition mechanism, DSTM is evaluatedthrough simulation using the Network Simulator ns-2 [11]. Inthe Figure 2, the network topology for the DSTM transition

    Figure 2. DSTM Simulation Scenario

    mechanism is shown. This topology is designed for thesimulation in ns-2.26 with  MobiWan  patch pack. Thetopology consists of two IPv4 hosts who want to communicatewith each other over an IPv6 network. IPv4 host (node N0)initiates packet transmission by sending request to the DSTMTSP (node N0). At this DSTM server, the IPv4 packet isencapsulated inside an IPv6 header of DSTM TSP (node N1).This IPv4 packet is carried inside the IPv6 header as the IPv6

     payload. The packet is forwarded inside the IPv6 network andfinally it arrives at the DSTM TEP (node N8). The DSTMTEP decapsulates the IPv6 packet and generates the IPv4address of the destination IPv4 Host (node N9). This is because instead of the destination node’s IPv4 address, theDSTM TSP forwards the packet in IPv6 network with theDSTM TEP’s IPv6 address. This IPv6 address is an IPv4-compatible-IPv6 address and it carries the correspondingdestination IPv4 address in the last 32-bits. Finally DSTMTEP delivers the packet to the destination IPv4 Host with thisIPv4 address. The link capacity between DSTM TSP server(node N1) and the IPv4 source (node N0) is 10Mbps andtransmission delay is 20ms. Similarly the link capacity

     between the DSTM TEP server (node N8) and the IPv4destination node (node N9) is 15Mbps and transmission delayis 15ms. All other links are of equal capacity with 10Mbpsand a 12ms transmission delay. With these parameters, meanend-to-end delay is computed for these different applications:RA (Real Audio), FTP and CBR.

    V.  R ESULTS A ND DISCUSSIONS

    We compute the mean end-to-end delay for IPv4-onlynetwork as well as for IPv4 and IPv6 network with the DSTMenabled. The end-to-end delay has been calculated for varying packet sizes for the same network architecture. The trafficflow is also varied for FTP, RA and CBR. The mean end-to-end delay is calculated by taking into consideration of the timeat which a packet starts at the source and the time at which the packet reaches the destination, and also the number of packetsreceived as given in (1). This information is extracted fromthe trace file obtained for the corresponding tcl script used forthe simulation, with the help of a perl script. 

     Mean end-to-end delay: DE m

     N 

    i

    i

    m N 

     D

     DE ∑=

    =1

     

    Di = end-to-end delay of packet “i” = Tdi - Tsi (second)Tsi = Time of packet “i” en-queued at source

    Tdi = Time of packet “i” received at destination Nr  = Number of packets received at destination

    The data obtained is shown in Table I and Table II. Thesetables show the data for IPv4-only network and IPv4 versusIPv6 network with DSTM, respectively. It is observed thatwhen packet size increases, more time will be consumed fordelivering the packet to the destination node due to the higher payload and hence increases the queuing delay for each packet. The RA (Real Audio) traffic consumes maximumtime as it is real-time application and hence also the payloadwill be more. The CBR gives the shortest delay as the bit rateis constant and it uses UDP for transmission. Since UDP is aconnectionless protocol, it takes lesser delivery time than

    TCP. The delay for FTP traffic is more than CBR but less than

    DSTMTEP

    IPv4 HOST

    IPv4 HOST

    DSTM

    TSP

    IPv6 NETWORK

    (1)

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    RA since it uses TCP for transmission. As TCP is aconnection oriented protocol, it takes higher delivery timethan UDP. It is also seen that there is significant increase inthe delay for CBR and RA traffic when the packet size is 1256 bytes. The reason behind this is that the maximum limit of the packet size that can be transmitted for CBR and RA traffic is1000 bytes. Therefore whenever the traffic with packet sizemore than 1000 bytes is encountered, it is split and transmitted

    and hence increases the delay. When the mean end-to-enddelay for IPv4-only network and IPv4 versus IPv6 networkwith DSTM is compared, it is found that IPv4 versus IPv6network consumes more time to deliver a packet. Thishappens because when the IPv4 node forwards a packet toanother IPv4 host through IPv6 network, the encapsulationand decapsulation of the packet at the DSTM server, TSP(when the packet enters the IPv6 network) and the otherDSTM server, TEP (when the packet leaves the IPv6network), respectively, takes considerable amount of time andso increases the queuing delay. So the communication between IPv4 hosts over an integrated IPv6/IPv4 networkusing DSTM will always take longer than the communication

     between the hosts in IPv4-only network or in IPv6-onlynetwork.

    TABLE I

    MEAN E ND-TO-E ND DELAY FOR IPV4-O NLY NETWORK  

    Packet Size(Bytes)

    FTPEnd-to-EndDelay(ms)

    RAEnd-to-EndDelay(ms)

    CBREnd-to-EndDelay(ms)

    256 60 140 50

    512 70 142 65

    1000 82 160 76

    1256 107 235 98

    TABLE II

    MEAN E ND-TO-E ND DELAY FOR IPV4 A ND IPV6 NETWORK (WITH DSTM) 

    Packet Size(Bytes)

    FTPEnd-to-EndDelay(ms)

    RAEnd-to-EndDelay(ms)

    CBREnd-to-EndDelay(ms)

    256 100 180 80

    512 110 180 95

    1000 115 190 103

    1256 140 310 132

    VI. CONCLUSION

    This research is just an attempt to show the current scenario

    of the impact of transition mechanisms over a network. Itreflects the performance overhead incurred by DSTM ascompared to an IPv4-only network. This work also concludesthat in spite of imposing extra delay to the network, the DSTMis significant as a transition mechanism due to two facts.Firstly, a transition mechanism is required for the smoothinteroperation of both the protocols and secondly, DSTM has proved to have several features of tunneling and dual-stackapproach which can be considered as an intermediate of thesetwo transition mechanisms. This way DSTM provides betterreliability and low data loss by combining the features of thetwo transition mechanisms. This research will encourage thescientists across the globe to explore more on many other

     parameters to perform a comparative study of the varioustransition mechanisms.

    R EFERENCES

    [1] G. C. Kessler, IPv6: “The Next Generation Internet Protocol,” theHandbook on Local Area Networks, pub. Auerbach in August 1997.

    [2] Jivesh Govil, Jivika Govil, et al, “On the Investigation of Transactionaland Interoperability Issues between IPv4 and IPv6,” IEEE EIT 2007Proceedings, 2007, vol-2,200-203p.

    [3] T. Sanguankotchakorn et al., “Performance Evaluation of IPv6/IPv4Deployment over Dedicated Data Links,” Fifth International Conferenceon Information, Communications and Signal Processing, 2005.

    [4] Myung-Ki Shin et al., “An Empirical Analysis of IPv6 TransitionMechanisms, Feb. 20-22, 2006 ICACT2006.”

    [5] Hatim Mohamad Tahir, Azman Taa, Norshakinah Bt Md. Nasir,“Implementation of IPv4 Over IPv6 Using Dual Stack TransitionMechanism (DSTM) on 6iNet,” Second International Conference onInformation and Communication Technologies, 2006, ICTTA '06, vol.2, pp. 3156-316, ISBN: 0-7803-9521-2

    [6] Xiaoming Zhou et al., “Estimation of Perceived Quality of Service forApplications on IPv6 Network,” Proceedings of the ACM internationalworkshop on Performance monitoring, measurement, and evaluation ofheterogeneous wireless and wired networks 2006, pp. 74–81, ISBN:1-59593-502-9

    [7] Eun-Young Park et al., “An IPv4-to-IPv6 Dual Stack TransitionMechanism Supporting Transparent Connections between IPv6 Hosts and

    IPv4 Hosts in Integrated IPv6/IPv4 Network,”  IEEE CommunicationSociety 2004.

    [8] Tian, J. and Li, Z., The next generation Internet protocol and its test,  IEEECommunication Magazine, 210-215, 2001.

    [9] Francisco J. Ros, Pedro M. Ruiz. Implementing a New Manet UnicastRouting Protocol in NS2, December 2004.

    [10] http://www.inrialpes.fr/planete/mobiwan.[11] The VINT Project. The ns Manual, December 2003, http:// www.isi.edu/ 

    nsnam/ns/ns-documentation.html.