Tejal Arvind Sonawale, Dr Shikha Nema / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.259-263259 | P a g eComparison of Routing Protocol in MANETs*Tejal Arvind Sonawale, **Dr Shikha Nema*M.E(EXTC) V.E.S.I.T,Chembur Mumbai, India**EXTC V.E.S.I.T,Chembur Mumbai, IndiaAbstractAOMDV is widely used protocol thesedays. But, its permissive for link failure. It takesthe necessary action after detecting the linkfailure thus holding/queuing packets till newroute is discovered after detecting failure inexisting link.. Early Link Failure Detection-AOMDV (ELFDAOMDV) keeps on monitoringdistance between two mobile nodes. As soondistance between two nodes crosses specifiedthreshold then it sends a request to source nodeto start discovering new route but continues totransfer data packets as the link is still up. Inmost of the cases, new route is discovered (if someexists) before link failure. Then using theintelligence data packets are automaticallyshifted to this newly discovered route, thuspreventing the link failure. Hence, the algorithmis named as Early Link Failure Detection -AOMDV.Keywords- Ad hoc networks; Routing protocols;AODV, DSR, AOMDV.1. INTRODUCTIONIn contrast to infrastructure based wirelessnetworks, in ad hoc networks all nodes are mobileare connected dynamically in an arbitrary manner. Acollection of mobile host with wireless networkinterfaces may form a temporary network withoutthe aid of any established infrastructure orcentralized administration.In the case where only two hosts, within thetransmission range, are involved in the ad hocnetwork, no real routing protocol or routingdecisions are necessary. But in many practical adhoc networks, two hosts that wish to communicatemay not be close enough within wirelesstransmission range of each other. These hosts couldcommunicate if other nodes between themparticipated willfully to forward packets to thedestination or the next hop towards the destination.So all nodes behave as routers and take part indiscovery and maintenance of routes to other nodesin the network. Route construction should be donewith minimum overhead and bandwidthconsumption.1.2 AD-HOC NETWORK DESIGN ISSUESThe Ad Hoc architecture has many benefits,such as self-reconfiguration, ease of deployment,and so on. However, this flexibility and conveniencecome at a price. Ad hoc wireless networks inherit thetraditional problems of wireless communications,such as bandwidth optimization, power control, andtransmission quality enhancement, while, inaddition, their mobility, multi-hop nature, and thelack of fixed infrastructure create a number ofcomplexities and design issues that are specific tomobile ad hoc networks. Infrastructure-less Dynamically Changing NetworkTopologies Physical Layer Limitations Limited Link Bandwidth and Quality Variation in Link and Node Capabilities Energy Constrained Operation Network Robustness and Reliability Network Security Network Scalability Quality of Service2 ROUTING PROTOCOLMany protocols have been proposed for adhoc networks, all fall in any of the three sets, namelyTable-Driven, Source-Initiated On-Demand, andZone based.2.1Table-Driven Routing ProtocolsTable-driven routing protocols attempt tomaintain consistent, up-to-date routing informationfrom each node to every other node in the network.These protocols require each node to maintain one ormore tables to store routing information, and theyrespond to changes in network topology bypropagating updates throughout the network in orderto maintain a consistent network view. The areas inwhich they differ and the number of necessaryrouting-related tables and the methods by whichchanges in network structure are broadcast2.2 Source-Initiated On-Demand RoutingA different approach from table-drivenrouting is source-initiated on-demand routing. Thistype of routing creates routes only when desired bythe source node. When a node requires a route to adestination, it initiates a route discovery processwithin the network. This process is completed once aroute is found or all possible route permutationshave been examined. Once a route has beenestablished, it is maintained by a route maintenance
Tejal Arvind Sonawale, Dr Shikha Nema / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.259-263260 | P a g eprocedure until either the destination becomesinaccessible along every path from the source oruntil the route is no longer desired.2.3 Zone Routing ProtocolZRP divides its network in different zones.Thats the nodes local neighborhood. Each node maybe within multiple overlapping zones, and each zonemay be of a different size. The size of a zone is notdetermined by geographical measurement. It is givenby a radius of length, where the number of hops isthe perimeter of the zone. Each node has its ownzone.Advantage less control overhead as in a proactiveprotocol or an on demand protocolDisadvantage short latency for finding new routes3 SECURITY IN AD HOC NETWORKThe security needs of Ad Hoc Network are notdifferent from the traditional networks Confidentiality Availability Integrity Authentication Non-repudiation Link Level Security Secure RoutingWireless technologies are unequivocally among themost rapidly progressing technology sectors. Thereis a vast range of wireless technologies, applicationsand devices, which are either already a substantialpart of our daily life or could play this role in future.Wireless ad hoc networking is one of theseapplications, which can potentially enhance ourabilities to solve real life challenges.4. ROUTING Protocol Approach4.1. Adhoc on demand Multi-path distancevector(AOMDV)Adhoc On-demand Multi-path DistanceVector (AOMDV)  is an extension to theAODV. The main difference lies in the number ofroutes found in each route discovery. A littleadditional overhead is required for the computationof multiple paths. This protocol does not require anyspecial type of control packets but makes use ofAODV control packets with a few extra fields in thepacket headers. The AOMDV protocol computesmultiple loop-free and link-disjoint paths. There arethree phases of the AOMDV protocol. The firstphase is the Route Request, second is the RouteReply and the third phase is the Route Maintenancephase. Route Request:The protocol propagates RREQ from sourcetowards the destination. Node S as in AODVbroadcasts multiple requests to its neighboring nodes1 and 2. This means that request with samesequence numbers are sent to the destination node.They further broadcast the request to the otherneighboring nodes, which are further sent to thedestination node D. Route Reply:The protocol establishes multiple reversepaths both at intermediate nodes as well asdestination. Multiple RREPs traverse these reversepaths back to form multiple forward paths to thedestination at the source and intermediate nodes. Ifthe intermediate nodes have the route defined for thedestination then they send the RREP to the sourcenode S. The protocol is designed to keep track ofmultiple routes where the routing entries for eachdestination contain a list of next hops together withthe corresponding hop counts. All the hop countshave the same sequence number then the path withthe minimum hop count is selected and all the otherpaths are discarded. The protocol computes multipleloop-free and link-disjoint paths. Loop-freedom isguaranteed by using a notion of “advertised hopcount”. Each duplicate route advertisement receivedby a node defines an alternative path to thedestination. To ensure loop freedom, a node onlyaccepts an alternative path to the destination if it hasa lower hop count than the advertised hop count forthat destination. The advertised hop count isgenerally the maximum hop count value possible fora node S to reach a node D. If any value that isreceived by the source S is greater than theadvertised hop count value then a loop is formed sothis RREP is discarded. The multiple RREPs arereceived by the source via multiple paths and aminimum hop count route is selected, the otherroutes carrying a higher hop count value arediscarded.Destination is the node where the packet isdestined to, the sequence number to maintain thefreshness of the routes, the advertised hop count thatavoids the formation of loops. The route list consistsof Hop Count required to reach a particulardestination, Next Hop is the next hop the packet issupposed to take to reach the required destination,Last Hop is the last hop taken to reach thedestination. If the packet is following the same paththen this value is same as the Next Hop or else itchanges and Expiration Timeout is the time forwhich the path will exist. There are multiple entriesfor a single destination but the routes that contain thelowest hop count are only recorded in the routingtable and the other routes are discarded.
Tejal Arvind Sonawale, Dr Shikha Nema / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.259-263261 | P a g e Route Maintenance Phase:The third phase is the Route MaintenancePhase. This phase works in exactly same as AODV.If the intermediate nodes are not able to receive aresponse of the HELLO message then they broadcasta Route Error message. After receiving this messageall the nodes that use the particular route to reach thedestination make this particular route as infinity andinform the source node to run a fresh routediscovery.There are two types of disjoint paths, one isthe node disjoint and the other is the link disjoint.Node-disjoint paths do not have any nodes incommon, except the source and destination. The linkdisjoint paths do not have any common link.An AODV protocol is been developedwhich develops route on-demand. The biggestdrawback of AODV is with respect to its routemaintenance. If a node detects a broken link whileattempting to forward the packet to the next hop thenit generates a RERR packet that is sent to all sourcesusing the broken link. The source runs a new routediscovery after receiving RERR packet. Thefrequent route breaks cause intermediate nodes todrop packets because no alternate path to destinationis available. This reduces overall throughput, packetdelivery ratio and increases average end-to-enddelay if there is high mobility. The other drawback isthat multiple RREP packets are received in responseto a single RREQ packet and can lead to heavycontrol overhead. The HELLO message leads tounnecessary bandwidth consumption.The AOMDV is an extension to the AODVprotocol for computing multiple loop-free and link-disjoint paths. The protocol computes multiple loop-free and link-disjoint paths. Loop-freedom isguaranteed by using a notion of “advertised hopcount”. Each duplicate route advertisement receivedby a node defines an alternative path to thedestination. To ensure loop freedom, a node onlyaccepts an alternative path to the destination if it hasa lower hop count than the advertised hop count forthat destination. With multiple redundant pathsavailable, the protocol switches routes to a differentpath when an earlier path fails. Thus a new routediscovery is avoided. Route discovery is initiatedonly when all paths to a specific destination fail. Forefficiency, only link disjoint paths are computed sothat the paths fail independently of each other.In AOMDV RREQs reaching the nodemay not be from disjoint paths, if RREQ is from onecommon node one of the RREQ is discarded, thismessages implicitly provide knowledge about themobility and accessibility of their sender andoriginator. for example, if node A is constantlyreceiving messages initiated by another node B, thisimplies that node B is relatively stationary to nodeA. furthermore a valid route from node A to node Bis available either directly or through other nodes.Instead of discarding repeated RREQs messagesnode can perform additional computation onavailable routing data and predict accessibility ofother nodes.Now AOMDV routing make use of pre-computed routes determined during route discovery.These solutions, however, suffer during highmobility because the alternate paths are not activelymaintained. Hence, precisely when needed, theroutes are often broken. To overcome this problem,we will go for link breakage prediction. Predictionwill be done only for multiple paths that are formedduring the route discovery process. All the paths aremaintained by means of periodic update packetsunicast along each path. These update packets areMAC frames which gives the transmitted andreceived power from which distance can bemeasured. This distance can be used to predictwhether the node is moving inward or outwardrelative to the previous distance value that is it givethe signal strength. At any point of time, only thepath with the strongest signal strength is used fordata transmission.4.2. Early Link Failure Detection AOMDV(ELFD-AODV)AODV is widely used protocol these days. But, itspermissive for link failure. It takes the necessaryaction after detecting the link failure thusholding/queuing packets till new route is discoveredafter detecting failure in existing link.ELFD-AOMDV keeps on monitoring distancebetween two mobile nodes. As soon distancebetween two nodes crosses specified threshold thenit sends a request to source node to start discoveringnew route but continues to transfer data packets asthe link is still up. In most of the cases, new route isdiscovered (if some exists) before link failure. Thenusing the intelligence data packets are automaticallyshifted to this newly discovered route, thuspreventing the link failure. Hence, the algorithm isnamed as Early Link Failure DetectionAOMDV.Logic to monitor the distance between two mobilenodes-Source mobile node cannot know thedistance till destination mobile node or co-ordinatesof destination mobile node. So, source node cannotcalculate distance from source to destination. Itfollows the reverse approach. Algorithm uses thefacts that each node knows the current co-ordinatesof self. While sending packets source nodes insertsits own co-ordinates in the header. Destination nodereceives the pakcet containing the source nodeidentification and co-ordinates of source node.Destination node calculates the distance betweensource and self as it knows its own co-ordinates andco-ordiantes of source node which are received inheader. If this distance crosses threshold thendestination nodes informs the source node by
Tejal Arvind Sonawale, Dr Shikha Nema / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.259-263262 | P a g esending packet that link may break soon. As soon assource node receives such packet, it starts lookingfor new node.5. Performance Metrics Comparison Packet Delivery Ratio – The ratio of totalnumber of data packets successfully received byall the destinations to the total number of datapackets generated by all the sources. Throughput: Throughput is total packetssuccessfully delivered to individual destinationover total time.SIMULATION RESULT AND ANALYSISChannel Type WirelessRadio Propagation Model TwoRayGroundNetwork interface typePhy/WirelessPhyMAC typeMac/802_11Interface Queue TypeDropTail/PriQueueAntenna Type OmniAntennaMax Queue Length 50No. Of Mobile nodes 06Routing protocol-AOMDV/ELFDAOMDVMobility Random Way Point ModelThroughput: Measure how soon the receiver isable to get a certain amount of data send by thesenderThroughput in kbps = ((Total size ofpackets transferred)/(StopTime -StartTime)) * (8/1000)Fig5.1 Throughput ELFD-AOMDV vs AOMDV Average throughput of AOMDV== 99.46 kbps Average throughtput ELFD-AOMDV==190.52 KbpsPACKET DELIVERY RATIOFig 5.2 Shows Packet Delivery Ratio of ELFD-AOMDV and AOMDVPacket Delivery Ratio = (No. Of Packets received/No. Of Packets sent) * 100. Generated Packets=2400 Received Packets=1118 PDR (AOMDV)=46.5833% Generated Packets=2572 Received Packets=2142 PDR (ELFD-AOMDV)== 83.28%6 CONCLUSIONIn MANETS’s due to movement of thenodes, network topology may change rapidly andunpredictably over time. In this decentralizednetwork, discovering the route and delivering of databecomes complicated. In mobility scenario alreadydeveloped routing algorithms like AOMDV givesdegraded results compared to ELFD-AOMDVperformance characteristics. ELFD-AOMDV cameup with the advantage of Increased Throughput andPacket Delivery Ratio.References www.ietf.org/html.charters/manet-charter.html Murthy, S. and J.J. Garcia-Luna-Aceves,An Efficient Routing Protocol for WirelessNetworks, ACM Mobile Networks andApp. J., Special Issue on Routing in MobileCommunication Networks, Oct. 1996, pp.183-97. C. E. Perkins and P. Bhagwat, “HighlyDynamic Destination-Sequenced Distance-Vector Routing (DSDV) for Mobile
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