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Nakhaee et. al.sends data packets using this route immediately.Otherwise, route discovery procedure begins. Wemodified the procedure as follows:Step1: A source node starts to flood RREQ packets toits neighboring nodes in a MANET until they arrive attheir destination node. We add two numbers qmean andmaxq to these RREQ packets.Step2: If the intermediate node N receives a RREQpacket and it is not the destination, then the new valuesof maxq and qmean are calculated in node N. Andinformation of node N is added to the RREQ packetwhich is appended to packet fields. After that, node Nreforwards the packet to all the neighboring nodes ofitself.In node N, maxq is changed if the maximum queuelength in the node is higher than the current maxq in theRREQ received message. Equation (1) shows how tocalculate qmean in the node N.(1)Step3: If node N receives a RREQ packet and node Nis the destination, it waits a period of time. Therefore,the destination node may receive many different RREQpackets from the source. Then it calculates the value ofreliability value for each path from source to thedestination using the information in each RREQ packet.Equation (2) shows how to calculate reliability value(R_degree). Finally, destination node sends a RouteREPly (RREP) packet along the path which has amaximum reliable value.(2)Variable nohop presents hop numbers in routing.We exceeds with presenting a CPN model formodified AODV protocol. Our model is based on themodel which is presented by xiong et al. We considerAODV protocol has four states [9]: RoutCheck: Check the route table to see if the nodehas an existing and valid path to the destination. RREQInit: Initiate RREQ message when necessary. RREQProcess: Process the incoming RREQmessage and output proper results.RREPProcess: Process the incoming RREP messageand output proper resultsIII. CPN MODEL OF A MANET WITH AODV ROUTINGPROTOCOLA. Colored Petri NetsColoured Petri Nets were introduced by Kurt Jensenin 1987 as a developed model of Petri Nets. ColouredPetri Nets are appropriate tools for mathematical andgraphical modeling. Coloured Petri Nets have numerousapplications, and lots of research has taken place withrespect to modeling, describing and analyzing systems,which have synchronized, asynchronized, distributed,parallel, non-deterministic or random natures. In fact,Petri Nets are models which could represent theperformance and state of the system at the same time.A formal definition of CPN is as follows [8]:A Coloured PN (CPN) is a 6-tuplewhere1) P = denotes a finite and non empty setof Places.2) T = denotes a finite and non empty setof Transition.3) C is a colour function that assigns a finite and nonemptyset of colors to each place and a finite and nonemptyset of modes to each transition.4) Denote the backward and forwardincidence functions defined by , such thatDenotes a function defined on P, describing theinitial marking such thatB. CPN Model for Modified AODV Routing ProtocolThe hierarchy page (Jensen) of our CPN model isdepicted in Figure 1. It explains the overall organizationof the modules comprising the CPN model of ourMANET. Page Prime#1 is the top level of our Model fora MANET. And the second level (page Node#2) is thenode template for implementing AODV protocol. Herewe can create model for any MANET composed ofnodes as many as allowed by instantiating this nodetemplate using CPN TOOLS [10]. The third level hasthree pages (page RREQInit#4, page RREQProcess#5and RREPProcess#6), each of which is named by anAODV state as given in [9]. Page SendMsg#3 sendsnode messages in the network.Fig. 1. The hierarchy pageIf we want to create a node instance in a MANET, wecan simply do it by instantiating the node template. Likean object in an object oriented programming language,every instantiated node has its own local variables andprovides interface to the outside world. In our CPN242 | P a g e