多跳扩展网络NS2.docx

1、多跳扩展网络NS2A Multi-homing Extension of Wireless NodeImplementation in NS-2Qinghua Wang,Tingting ZhangDepartment of Information Technology and MediaMid Sweden University,85170Sundsvall,SwedenEmail:qinghua.wang,tingting.zhangmiun.seAbstractDue to the rapid growth of wireless communication, it is now bel

2、ieved that wireless devices with multiple interface support will highly increase in the near future.In the research community of Network Simulator,there has recently been quite a large interest in extending the current wireless node implemen-tation so as to be able to include more than one radio int

3、erface to work simultaneously.We focus our efforts on the extension of multi-homing ability of ns-2,which has been the most used network simulator in wireless network research.Multi-homing here is dened as the ability of a single end-point to support multiple IP addresses by the use of multiple inte

4、rfaces.The ns-2simulation environment is aexible tool for network engineers to investigate how various protocols perform with different congurations and topologies. However,the support for wireless and mobile networking in ns-2is monolithic and not entirely consistent with basic design principles so

5、 that it makes it quite difcult,if not impossible, to extend a multi-homing support based on current mobilenode design.This paper describes how we extend the ns-2framework to include support for an imititated wireless multi-homed node.Index TermsMulti-homing,multiple interfaces,ns-2.I.I NTRODUCTIONI

6、n recent years the tremendous success and demand met by wireless technologies,have fostered a considerable amount of research work ranging from propagation models,radio planning,power consumption,medium access,routing pro-tocols to QoS and security issues.Topics such as mobile ad-hoc networks(MANETs

7、and wireless sensor networks for instance have been the focus of a lot of studies and papers during the last few years.In the MANETs and sensor network research community,a lot of studies have been based on the simulation.And among the network simulators,ns-21has been used in nearly half of them and

8、 become a de facto standard,if we refer to6.The object-oriented design of ns-2allows for straightfor-ward creation and use of new protocols.The combination of easy in protocol development and popularity has ensured that a high number of different protocols are publicly available, despite not all of

9、which are included as part of the simulators release.Its status as the most used MANETs simulator has also encouraged further popularity,as developers would prefer to compare their work to results from the same simulator. However,ns-2is currently not perfect in supporting MANETs simulation research.

10、It does not support well for some important features.An example of such a feature needed today is the multi-homing ability for a wireless node.A multi-homed node is dened as a node that enjoys the ability of supporting multiple IP addresses simultaneously,and this kind of ability is usually implemen

11、ted by adding multiple interfaces, including wired and wireless interfaces,in a single node.The utilization of a multi-homed node can be versatile.For exam-ple,the feature of redundancy in interface numbers can be used to provide reliable transmission and increase the survivability of the session in

12、 the presence of network failures,such as what The Stream Control Transmission Protocol(SCTP3 is doing.Another important utilization is to use the multi-homed node as a communication switcher in a heterogenous network.A network can become heterogenous because of different reasons,such as the need of

13、 the cohabitation be-tween a network with updated protocol and an old network, or network with nodes coming from different providers,or simply different type of networks needing to communicate. In this case,the multi-homed node must possess the ability in forwarding and translating packets among dif

14、ferent types of connected networks.A sketch graph of one heterogenous network interconnected by multi-homed nodes is shown in Fig. 1.In this paper,we extend the current ns-2wireless node design to support the ability of multi-homing,so it can be used to perform the simulation of the heterogenous wir

15、eless network interconnection.In the following of this paper,Section II introduces the ns-2 wireless node design and the existing efforts in extending its multi-homing ability.Section III further details the wireless node design in current ns-2release,which is the basis of our multi-homing extension

16、.Section IV then gives the design details of our multi-homing extension.An initial ns-2imple-mentation of the presented multi-homing extension is given in section V.Finally,the conclusion is given in section VI.II.R ELATED WORKNs-2is the most popular simulation tool for MANETs.It began as ns(Network

17、 Simulatorin1989with the purpose of general network simulation.Its wireless and mobile net-working support extension is originally developed by CMU Monarch group2in the late1990s and later integrated in the mainline code.The primary purpose of this extension was to enable simulation of wireless netw

18、orks,in particular multihop ad hoc networks.The support of sensor network simulation Multihomed NodeFig.1.An interconnected heterogenous MANETin ns-2is also based on CMU Monarch extension,with a small number of add-ons.The CMU Monarch extension will be further detailed in Section III and our wireles

19、s multi-homed node extension will be based on the CMU Monarch wireless node design.There is actually already one multi-homing implementation included in current ns-2release.It is the implementation of The Stream Control Transmission Protocol(SCTPprovided by University of Delaware.However,its not a s

20、atisfying solution for the multi-homing requirement of MANETs.The rst argument,against the use of SCTP for the realization of multi-homing in MANETs,is that the multi-homing in current SCTP implementation is only used for the transport redundancy between exactly two endpoints,and it does not support

21、 the interconnection in a heterogenous network,which however is our focus.The second argument is that the multi-homing feature in current SCTP implementation is not an independent feature and always need to be used together with SCTP,which however suppresses the use of other transport protocol,such

22、as TCP and UDP.The last argument is that the support of SCTP in the existing Internet infrastructure and MANETs is minimal.An extreme example is the redundantly deployed sensor network,where transmission reliability is not so important and a connectionless transport protocol similar to UDP is prefer

23、red for the saving of limited energy.In Ref.5,the authors try to(in the format of a howto address all the changes that are needed on ns-2source code (both TCL and C+so as to be able to extend current wireless node implementation to support multiple interfaces.However,in the current wireless node stu

24、cture,only a single routing agent can be attached.The manual of ns-27said that a wireless node may have more than one interfaces,it is assumed that a unique routing protocol agent runs over all the interfaces. What Ref.5can help is to support such kind of multiple interfaces.Not to mention massive o

25、f technical work needs to be done to support such a multiple interface implementation, such kind of support is not sufcient for the interconnection requirement of heterogenous MANETs.Researchers in the university NTNU realized the insuf-ciency in current ns-2wireless node design,and thought the curr

26、ent wireless node design has made it difcult to extend new features8.Thus they provided a modied design of ns-2wireless node,and based on this modied wireless node design,a multiple interface wireless node with each interface attached with an independent routing agent can be easily built. The drawba

27、ck is that this modied wireless node design is not included in the ns-2release currently and there are few publicly available mobile protocol implementations that can support this modied design,although it is considered to be more reasonable.Another drawback of Ref.5proposal and NTNU pro-posal8is th

28、at although multiple interfaces can be sup-ported by their proposals,all interfaces must share the same Source/Sink agent.That means,all interfaces must share the same IP address,since a Source/Sink agent must and can only be bound with a static IP address in the current implementation.According to

29、the denition of multi-homing, both these two proposals can not provide the real sense multi-homing ability for a wireless node.It may however be interesting to take a look at the ns2-MIRACLE framework9,where multiple modules are al-lowed to coexist within each layer of the protocol stack.Thus multi-

30、homing may be supported using their framework.In this paper,we are not going to present a subversive redesign of the ns2structure,rather than provide a short cut of implementing multi-homed node with a few add-ons.III.C URRENT WIRELESS NODE DESIGN IN NS-2This section gives a brief overview of the wi

31、reless net-working support in ns-2,originally developed as extensions to ns-2by the CMU Monarch group2.Each wireless node is an independent entity that is responsible for computing its own position and velocity as a function of time,and each wireless node consists of a series of components.Basically

32、, these wireless node components follow the ISO network stack. The physical layer includes radio propagation models,radio in-terfaces with adjustable parameters such as transmission power and receiver sensitivity and antennas models.The link layer includes medium access control(MACprotocols needed in such environment,and in addition address resolution protocol (ARPfor the MAC address translation in any outgoing IP packet.The network layer are implemented as a routing agent. All these entities are linked up together inside the wireless node.Fig.2shows the basic schematic layout of a typical