A Misbehavior-Tolerant Multipath Routing Protocol for Wireless Ad ...

A Misbehavior-Tolerant Multipath Routing Protocol for 

Wireless Ad hoc Networks 

Hanie Sedghi, MohammadReza Pakravan, MohammadReza Aref 

Department of Electrical Engineering, Sharif University of Technology, Tehran, Iran 

h.sedghi@ee.sharif.edu pakravan@sharif.edu aref@sharif.edu 

I. ABSTRACT 

Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several 

types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to 

behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior- 

Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, 

wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it 

uses a novel data redirection method to mitigate the impact of node misbehavior on network performance. The proposed 

scheme promises establishing a safe route if network graph remains connected after eliminating the misbehaving nodes. We 

have implemented the proposed protocol in a simulation environment and have evaluated its performance in typical network 

configurations to demonstrate its resilience to node misbehavior. 

III. CONCLUSION 

The proposed protocol addresses several types of node misbehavior in ad hoc networks. Previously proposed schemes are 

of two types: ones who only use network overview and the others who only take care of security issues and fail to notice the 

whole network picture. The first advantage of our scheme is that it considers both aspects. It can therefore detect and punish 

misbehaviors: selfish attacks, wormhole, sinkhole, grey-hole and data repetition and modification in forwarding phase. 

Moreover, in contrast to credit-based methods, several reputation-based methods and various previously suggested schemes, 

our solution does not need a center or a prior trust among nodes which makes it more suitable for ad hoc environment. 

Moreover, it does not require additional added complexity of extra hardware such as GPS or a precise global clock required 

by some other methods. Reputation-based methods share the goal to reduce the throughput of selfish nodes. Having reached 

this aim for all types of misbehavior addressed in this paper, we also introduced adaptive data redirection with a low 

overhead to minimize the impact of such adversaries on network throughput and service availability. The major advantage is 

that misbehavior detection and data redirection is performed with minimum data loss. The strict confronting method used, 

reduces the opportunity of the misbehaving nodes to use network resources which leads to a higher incentive to cooperate and 

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Citation 

H. Sedghi, M.R. Pakravan , M.R. Aref, “A Misbehavior-Tolerant Multipath Routing 

Protocol for Wireless Ad hoc Networks,” International Journal of Research in Wireless 

Systems (IJRWS), Vol. 2, No. 2, pp. 6-15, June, 2013 

ISSN: 2320 - 3617 

International Journal of Research in Wireless Systems (IJRWS), Volume 2, Issue 2, June (2013) 6

A Misbehavior-Tolerant Multipath Routing Protocol for Wireless Ad hoc Networks 

I. INTRODUCTION 

Wireless ad-hoc networks are becoming increasingly 

popular with a diverse range of applications. In many ad-hoc 

networks, nodes act as a source, destination or router of 

information. Therefore, a packet may pass multiple hops, being 

forwarded by interim nodes acting as routers, to reach its 

destination. If some nodes within an ad-hoc network do not 

route properly, due to reasons such as selfishness, the network 

cannot function as expected. Therefore, misbehavior of nodes 

can severely impact proper operation of the network. 

Ad hoc nature of the network implies that there are no 

infrastructures or central control system in the network. Also, 

nodes have limited radio range, computational power and 

battery power. This makes such networks vulnerable to several 

attacks such as wormhole, sinkhole, grey hole, impersonation, 

flooding, misleading routes and selfish attacks [1]. 

Wormhole attack is believed to be one of the most severe 

active attacks. Attacks performed by malicious nodes who 

deliberately try to harm network performance are called 

active. Wormhole is the creation of a tunnel between two 

colluding nodes linked through a private network connection. 

This exploit allows them to short-circuit the normal flow of 

routing messages by falsifying the widely-used hop count 

metric [2]. 

One prominent idea for detecting a wormhole was based 

on packet leashes [3]. This scheme needs authenticating either 

an extremely precise timestamp or location information 

combined with a loose timestamp. Therefore it is not 

applicable in ad hoc networks. Another approach uses hash 

chain and public key infrastructure to detect a wormhole [4]. 

As a result of ad hoc nature, a CA (Certificate Authority) is 

not an easily applicable assumption. Therefore public key 

infrastructure implementation is a challenge. Moreover, the 

scheme falsely accuses all benign nodes that happen to be on 

the same route as the wormhole. 

In many types of ad hoc networks, nodes have limited 

energy and computational power. Therefore, nodes will benefit 

from executing algorithms that keep their resources to 

themselves and that may result a selfish behavior in the 

network. Selfish nodes may not participate in routing data 

packets that does not belong to them, saving their resources. A 

game-theoretic approach to encourage energy sharing for 

packet forwarding is proposed in [5]. Selfish behavior 

introduces a type of denial of service (DoS) attack. In addition 

to denial of service, selfish behavior results in route loss, data 

loss, throughput reduction and in the worst case, network 

decomposition. It should be noted that, in comparison with 

other known attacks, this attack is not performed by nodes that 

have the tendency to hurt network, namely malicious nodes. It 

is done by normal nodes who behave rationally to save their 

resources. Considering the mentioned threats, it is of high 

importance to mitigate these types of misbehavior. 

Most ad hoc networks are composed of individual nodes all 

having the same priority. Therefore, preventing selfishness can 

be reached by enforcing cooperation [6]. These methods can be 

divided to credit-based methods and reputation-based methods. 

Credit-based methods use economic incentives to encourage 

packet forwarding. Cooperation is a service that can be 

evaluated and charged. They use a virtual currency which is 

implemented by either a tamper-proof hardware -virtual money 

- or a virtual bank. When a node wants to send a packet, it 

needs to have the money required by intermediate nodes [7], 

[8], [9]. Reputation-based methods are based on building 

reputation amongst nodes. Packet forwarding increases node 

reputation. Only nodes having good reputation can send their 

data in the network and the route having the highest reputation 

is chosen. Therefore selfish nodes are punished and isolated 

[10] [11] [12] [13] [14]. These methods use two types of 

information: reputation information received from other nodes 

and first hand information which is the knowledge acquired by 

monitoring neighbors' behavior [6], [12]. Some reputationbased 

schemes use the idea of watchdog and pathrater [13]. 

Another approach introduced recently, is a proactive 

cooperation mechanism to detect and punish selfish power off 

[15]. The method cannot detect more sophisticated selfish 

attacks like selfishness type II that will be introduced shortly. 

We propose a robust multipath routing protocol which 

detects all types of wormhole and selfishness known so far 

with low data loss. Utilizing a proactive approach, we apply 

the idea of reputation which is updated based on first hand 

information and a simple but thorough method for earning and 

losing it. Proposed routing protocol uses an adaptive rerouting 

method to prevent complex misbehavior impacts, and also 

guarantees establishing a safe route if network graph remains 

connected after eliminating misbehaving nodes. We have 

implemented the protocol in a simulation environment and 

have evaluated its behavior in realistic network scenarios. 

The proposed method has the following salient features: 

1. It is simple and does not require a trusted third party, prior 

trust among nodes, GPS, precise clock and similar 

requirements which add to the system complexity. 

2. It can detect and bypass wormholes, sinkholes and greyholes 

successfully with a low overhead. 

3. It can accurately detect and re-act properly to both types of 

known selfish node behaviors. Most papers have not been 

completely successful in addressing both types. 

4. It uses first hand information which are obtained by a node 

itself and that prevents issues that could arise from rumor 

spreading. 

5. Wormhole or selfish nodes neighbors are not wrongly 

accused. 

6. It does Dynamic Rerouting with minimum data loss to 

defend network performance against data packet drop 

attacks. 

7. It does multipath routing to decrease rerouting overhead 

and achieves that with far less overhead compared to ideas 

applied before. 

8. It works well under congestion or link failures, temporary 

or long-lasting. 

9. It can be easily implemented on a 802.11 MAC. 



As a side improvement, we design a slightly more 

intelligent TCP, which fortifies our system greatly while 

defending against wormhole attack and makes our idea to 

outperform all existing protocols. 

The remainder of this paper is organized as follows: Part 

two gives an overview of considered attacks and their impacts 

on network. Misbehavior-Tolerant Multipath Routing (MTMR) 

protocol is introduced in part three. In part four we prove some 

of MTMR properties. Part five defines simulation software, 

scenarios and results. Finally we conclude the paper in part six. 

II. CONSIDERED ATTACKS 

A. Wormhole 

Wormhole is the creation of a tunnel between two colluding 

nodes linked through a private network connection. The 

colluding nodes pretend to be neighbors while they are far 

from each other. Therefore, if a routing protocol exploits hopcount 

metric, wormhole will always be interesting and 

selected to be on the routes. The attraction of network traffic 

to wormhole is regarded as if wormhole is short circuiting 

network traffic. Hop-count is a common metric used by most 

routing protocols. A wormhole pair can disrupt on average 

32% of all communications across the network [4]. Most 

proposed routing protocols have no means to detect 

wormholes or rely on not applicable or unfair ideas. The worst 

case attack happens when colluding nodes forward route 

discovery messages but refuse to forward data packets. This 

subtle misbehavior drastically degrades network performance. 

B. Selfishness 

Selfish behavior addressed so far, can be classified into two 

categories that are called selfishness type I and II. In the type I 

selfish behavior, the selfish node does not participate in route 

discovery process to avoid being on the route. This behavior 

has also been named selfish power off. In the type II selfish 

behavior, the selfish node participates in route discovery phase, 

forwarding the control packets it receives but refuses to 

forward data packets. In addition, a node may change its 

behavior based on its remaining power, to act as a benign node 

first and change to being selfish based on its remaining power. 

Form our algorithm perspective; this will not make the process 

more complicated. A detailed explanation follows shortly. 

Selfish behavior degrades fairness in the network. Benign 

nodes consume their power in processing and forwarding 

packets of other nodes. In contrast, selfish nodes ignore other 

packets to keep their power to themselves. Moreover, 

selfishness makes benign nodes consume more energy. 

Considering selfishness type I, benign nodes will participate in 

more routes. If data retransmission is an issue in upper layers, 

Selfishness type II makes benign nodes forward more data 

packets. This includes the source node and intermediate nodes 

on a route that contains a selfish node type II. 

C. Sinkhole and Grey-hole 

In the sinkhole attack, the attacker spreads wrong routing 

information to attract network traffic to itself and discards the 

received traffic. A more complex form is the grey-hole attack, 

where the colluder forwards routing messages but discards 

data packets to keep its false route. 

Wormhole and Selfish attacks can have devastating effects 

on the performance of ad hoc networks which can be 

classified as a Denial of Service Attack. They can lead to 

network decomposition. Selfish power off may lead to failure 

in discovering a route. Wormhole and Type II selfishness 

attacks decrease packet delivery ratio drastically. Sinkhole and 

grey-hole can be considered as moderate wormhole attacks. 

III. MTMR PROTOCOL 

We propose a misbehavior-tolerant multipath routing 

protocol. Two major approaches are introduced in MTMR. 

First of all a proactive cooperation enforcement method is used 

to detect and punish misbehaviors and reward cooperation. 

Secondly, an adaptive data redirection method is used to 

mitigate offender's impact on network performance. 

A. Cooperation enforcement 

Cooperation enforcement is based on local measurements. 

In addition to a noticeable reduction in transmission and 

processing overhead, this approach makes network resilient to 

several attacks such as rumor spreading. Every node monitors 

its one-hop neighbors' relevant transmissions and based on 

their cooperation traces (CT), decides whether to cooperate 

with them or not. This routine is performed before routing 

decisions. 

The scheme is based on 5 basic operations. 

A table for keeping the traces: Each node maintains a table 

for its neighbors. The table contains node identity and the 

corresponding CT of its neighbors as shown in table1. Traces 

decrease in time so that a node who behaves well temporarily 

cannot take advantage of the given reputation for the rest of its 

presence in the network. 

2) A cooperation decision procedure: Received packet is 

processed and forwarded if and only if sender cooperation trace 

is not zero. 

3) A procedure to give CTs. We apply different strategies 

for adding or removing CTs based on packet type. 

Control Packets: If a node receives a control packet from a 

neighbor who is not the packet source, it shows the 

corresponding neighbor is cooperating, so the receiver 

increases the neighbor's CT. 

Data packets: Whenever a node forwards a data packet to a 

neighbor, it keeps track of the behavior of its neighbor. If the 

next hop forwards the packet, it is granted CT and if it refuses 

to forward the packet, its CT is reset. It should be noted that 

this observation is performed by adding the sent packets to a 

buffer. Each buffer entry has a timer assigned to it. Packets 

forwarded by neighbors (which in wireless medium can be 



received by the source as well as the next hop) are compared to 

buffer entries. If the forwarded packet is in the buffer, the entry 

is removed and the neighbor is granted a CT. On the other 

hand, if the timer is reset, it shows neighbor misbehavior and 

neighbor CT is reset. This approach fortifies the protocol 

against attacks that modify or repeat data packets in forwarding 

phase. The key idea is that if the misbehaving node changes or 

repeats the data packet, the new packet is not in the sender's 

buffer and the offender does not gain CT for that. In addition, if 

the offender does not forward the original packet at all, after 

corresponding buffer entry’s timer is expired, its CT is reset. 

CT is the key for acceptance in network. According to the 

cooperation decision procedure, if a node's CT is zero, the 

neighbor will not cooperate with it and such a node is 

punished. Considering nodes' limited resources, punishment 

entices such misbehaving nodes to act well. 

Granting CT is achieved by increasing node’s CT by size of 

packet cooperation value if the node is already in CT table, or 

by adding the neighbor to the CT table and giving it a CT equal 

to packet cooperation value in the other case. Different packet 

types have different cooperation values. 

4) A procedure to reset CTs: as mentioned above, CTs are 

decreased in time and reset if an offence is noticed. Therefore 

occasions may occur when parts of the network CTs have 

decreased in time and become zero. In such cases, a deadlock 

happens. 

5) A deadlock solution: Occasions may occur when a node 

or a part of network cooperation traces are expired. In this 

situation a deadlock occurs. To avoid this, when a source node 

detects a deadlock (by having its RREQ expired without 

receiving a RREP), it sets a Cooperation Request (CR) flag in 

its RREQ packet and broadcasts the RREQ. A neighbor 

detecting the flag from a source gives it a temporary CT and 

increases the counter for its credit requests, CR counter. A 

granted CT’s value is less than forwarding packet CTs. 

Moreover for each neighbor there is a limit on the number of 

CRs a node reacts to.‍CR flag is placed at RREQ packet's first 

hop field. The reason is that, this field is used in AOMDV [16] 

protocol but is not used in MTMR protocol. 

Table I. Cooperation Trace table 

Neighbor ID CT CR Counter 

N1 170 0 

N5 300 2 

… … … 

It should be noted that MTMR is fair and every node has 

the chance to join network by forwarding packets for others. 

Since cooperation enforcement procedure is performed before 

routing, edge nodes (i.e. nodes that are located at networks 

borders or are rarely chosen to be on a route) can gain CT by 

forwarding RREQs before duplicates are ignored by routing 

procedure. Therefore, border nodes and malfunction nodes are 

treated fairly. If some nodes are subject to some errors in MAC 

layer, this fairness helps them too. 

B. Multipath Routing and Data Redirection 

In order to minimize the impact of node misbehavior on 

network performance, it is not enough to punish offenders. It is 

needed to defend benign nodes throughput by finding safe 

routes. In order to reach this goal, we include a connection 

discovery phase in the protocol. A connection is a safe path 

without any misbehaving nodes. Connection discovery phase 

has two parts: route discovery and data redirection. Our 

multipath routing protocol is based on AOMDV (Ad hoc Ondemand 

Multipath Distance Vector) [16] but there are major 

differences. Like all other on-demand routings, when a source 

node wants to establish a connection, it broadcasts a Route 

Request packet (RREQ). Every node receiving a fresh copy of 

RREQ, updates its routing table with a new path to the source, 

and then searches its routing table to find a path to the 

destination. If a path is not found, it rebroadcasts the RREQ 

packet. Whenever a route to the destination is found or RREQ 

packet arrives at the destination, a Route Reply packet (RREP) 

is generated and sent to the source node. Unlike the AOMDV 

protocol who only finds at maximum three routes to the 

destination and sends back RREP on those discovered routes, 

we broadcast RREP packet to some hops. This is done so that 

nodes surrounding the discovered route get the information 

about destination whereabouts. This modification is of great 

importance to implement the data redirection method. 

Source responds to the first received RREP packet. The 

ones coming afterwards are only used for updating routing 

tables. After receiving the route reply packet, source checks the 

first entry in the routing table for the desired destination. It also 

checks the corresponding next hop CR, if the CR is not zero; 

source forwards the packet to the specified next hop. 

Otherwise, the second best next hop is analyzed and so on. 

This approach is followed by the intermediate nodes as well. 

A fresh copy is a copy of a RREQ/RREP that has not been 

received from the same neighbor before. Utilizing this 

definition along with sequence number and hop count assures 

loop freedom. 

If the discovered route contains a disobedient node, data 

packets will be retransmitted and redirected. In order to avoid 

loop in data redirection phase, data packets contain a sequence 

number. Sequence number also informs the intermediate node 

that the copy is a fresh copy, here, a retransmitted data packet. 

Considering mentioned procedures, data redirection is a 

straightforward decision. Any node receiving a fresh data 

checks its routing table and finds the first benign neighbor, i.e. 

the neighbor that owns a CR, and forwards the packet to it. If 

such a neighbor is not found, the node sends back the last data 

packet to the previous hop. In addition to optimizing data 

redirection, this operation prevents previous hop from falsely 

accusing the specified node. And hence, prohibits selfish 

spread. Selfish spread is the act of accusing benign nodes when 

they have no access to secure paths and thus do not forward 

packets. Several misbehavior detection mechanisms such as [4] 



suffer from this imperfection. Moreover, this algorithm assures 

stopping the data transmission in case of congestion or when 

the attack is so severe that the network is decomposed. As can 

be seen, this abrupt redirection fortifies the system against the 

third type of selfishness. 

This strategy promises minimum data loss. The reason is 

that, even if a misbehaving node exists on the path and it has a 

fake cooperation trace as a result of a CR, as soon as it drops 

the first data packet, previous hop is informed. Previous hop 

then resets the CT of misbehaving node and will not send the 

next data packet through the discovered misbehaving node. 

IV. MTMR PROPERTIES 

We introduce 6 properties of MTMR and provide heir 

proofs. 

Property I: If MTMR discovers a route between a source 

and its destination, the path is secure, i.e. it does not include 

misbehaving nodes. 

Proof I: Obviously, misbehaving nodes do not cooperate in 

forwarding control or data packets. Therefore, considering 

route discovery and connection discovery phase, selfish nodes 

type I will not be on the discovered route. Moreover, if a node 

is selfish type II, wormhole or sinkhole, it will be bypassed in 

rerouting of connection discovery phase. Consequently, only 

the nodes that forward data and ACK packets as well as 

RREQ and RREP packets can participate in a MTMR 

connection. Applying indirect proof, suppose that a 

misbehaving node resides on a MTMR route, therefore, it will 

at least ignore forwarding data packets or drops data packets. 

Noting the operation of MTMR as explained before, such a 

node can not be included in an MTMR path. This 

contradiction completes the proof. 

Property II: If MTMR discovers a route between source and 

destination, then at least one path exists from the source to the 

destination in the induced graph which is made by removing 

misbehaving nodes. 

Proof II: It can be easily deduced from property I that a 

MTMR-discovered path does not include misbehaving nodes. 

Therefore, the path that MTMR has discovered remains in the 

induced graph which is made by removing misbehaving nodes 

and it will not be cut. Hence, the statement is true. 

Property III: For every intermediate ad hoc node, MTMR 

protocol checks all of its neighbors once. 

Proof III: MTMR protocol strategy is as follows: If the 

intermediate node is connected to the destination, the source 

sends data to this node until the node tells the previous hop 

that it has processed all paths and cannot find a path to reach 

the destination. Therefore, the intermediate node rejects the 

data packet by returning it to the previous hop. 

After receiving a data packet towards the destination (D), 

intermediate node chooses the next hop specified by its table 

index for D. It always checks next hop CR before forwarding 

the packet. If the next hop specified by the table does not have 

a CR, the next table entry is checked and so on. If the 

intermediate node checks all the entries and does not find a 

benign next hop, it gives back the data packet. We apply 

inductive reasoning to show that. As induction assumption, 

suppose that if intermediate node is destination's k-th level 

neighbor (i.e. it is k-hop away from destination), all of its 

neighbors will be checked. Now consider the intermediate 

node of level k+1. Because of our limited directive flooding, 

all of this node's table entries for D are of level k. (Limited 

directive flooding means that in flooding phase, every node 

forwards the received RREQ/RREP to all its neighbors except 

the node that had flooded that packet in the previous step). 

According to induction assumption, all the neighbors for a 

node of level k are checked and finally that node sends a 

return message to the k+1-th level node .This way, the k+1-th 

level neighbor checks all its neighbors. 

Property IV: MTMR does not process any route twice. 

Proof IV: Since routes are processed solely by nodes that 

participate in them, if a route is processed twice it means there 

exists an intermediate node that has checked a specific 

neighbor twice. According to property III such a case is not 

possible. Since source node can be considered the last 

intermediate node (from destination side), it can be easily 

concluded from induction that there is no such probability for 

the source node too. 

Property V: Data packets follow the same path as RREQ 

packets. 

Proof V: This is due to the fact that intermediate nodes 

direct their routing tables as RREQ packets are flooded in the 

network. 

Property VI: MTMR processes loop-free routes. 

Proof VI: Considering the utilized strategy in route 

discovery phase, RREQ packets do not follow loops. The 

reason is that MTMR uses loop avoidance mechanisms such 

as SQN (Sequence Number) and limited directive flooding. 

Therefore, as a result of property V, data packets do not follow 

loops. 

V. SIMULATION 

Credit-based methods may not be appropriate for ad hoc 

nature. That is due to the fact that ad hoc networks lack 

infrastructure and certificate distribution centers. Therefore, 

ideas based on virtual currency or virtual bank will be difficult 

to implement in such networks. Moreover, there is no 

guarantee that intermediate nodes receive source money. It has 

been verified that if node density is not low, AODV [17] 

based multipath routing protocols (such as AOMDV) achieve 

a better performance and less routing overhead than DSR [18] 

based multipath routing protocols [19]. Data redirection has 

only been applied in [12] and it is based on DSR. Therefore, 

since MTMR is based on AODV, it uses a very low routing 

overhead compared to previously introduced schemes. 

Moreover, it uses a multipath routing method which is an 

efficient method in networks facing link breakage or mobility 

[16]. It also imposes less monitoring and processing load to 

the neighbor nodes compared to some watchdog based 

protocols [12], in which every node has to monitor all 

neighbors' traffic even when not addressed to it. Proactive 



cooperation mechanism used in [15] can only detect selfish 

power off. Proposed scheme does not use a threshold for 

detection. Threshold-based decisions [14] give misbehaving 

nodes the opportunity to use network resources. 

Therefore, to inspect proposed scheme behavior, MTMR is 

compared to defenseless scenario, AOMDV routing protocol. 

This is to inspect the pros and cons of intended misbehavioraware 

routing. 

We have designed a new network simulator named MARS: 

MAnet Routing Simulator to investigate the performance of 

the proposed protocol in realistic network scenarios. MARS is 

written in Visual C++ programming language and is designed 

for comparing different mobile ad hoc networks routing 

protocols. For the physical layer we used two-dimensional 

ground model and MAC layer is based on 802.11b. MARS 

benefits from a visual environment. Various network topology 

and node behavior parameters can be chosen by user. Packet 

exchange can be verified during simulation. Different paths 

traced by packets are shown with different colors. 

As stated in [16], AOMDV discovers "link-disjoint" paths. 

Rerouting is triggered in case of link breakage and considering 

the routing overhead, the best number for discovered paths is 

three. If the transport layer uses TCP protocol, it stops packet 

retransmission after 5 consecutive unacknowledged data 

packets [20]. 

MTMR to ITAOMDV as well as AOMDV in case of 

wormhole attack. 

Figure 1 One Traffic scenario, AOMDV protocol failure in case of one 

selfish node type II 

Figure 2 One Traffic scenario, MTMR success in detecting and bypassing the 

selfish node type II 

A. Overview 

First consider the network shown in figure 1. Network 

consists of 50 randomly positioned nodes. Node 6 is traffic 

source and node 30 is the destination. Both routing protocols 

are investigated: In case of AOMDV protocol if only one 

selfish node type II is present in the route, it will ignore all 

data packets and the source will not be aware of that. This is 

shown in figure1. Node 8 is the selfish node. Packet 

transmission is stopped by TCP after 5 consecutive 

unacknowledged data packets. RREQ traces are shown in 

blue. RREP, data and Ack packets traces are shown with 

yellow, pink and green consecutively. 

Figure 2 shows how MTMR reacts to the defined scenario. 

Node 18 detects the selfish node after it drops the first data 

packet and redirects the consequent data packets to node 39. 

As mentioned before, increasing the number of selfish node 

does not cause failure in discovering a safe route provided that 

network graph containing source and destination remains 

connected after eliminating selfish nodes. 

B. Wormhole Detection 

We propose a cross layer approach to improve AOMDV's 

performance in case of wormhole attack. Generally, if the 

transport layer uses TCP protocol, it hinders data 

retransmission when 5 packets are timed out. We design a 

more intelligent TCP that triggers redirection in case of 5 

consecutive unacknowledged packets. We call this cross layer 

design, Intelligent TCP AOMDV (ITAOMDV). We compare 

The considered sample network consists of 50 nodes 

randomly placed over a 100*100 m 2 area. Each node has a 

transmission range of 10 m. Each traffic session is assumed to 

contain 1000 data packets. We define Packet Delivery Ratio 

(PDR) as number of Ack. packets divided by number of 

generated data packets and we use it as the comparison 

benchmark. If no benign path exists between source and 

destination, MTMR refuses to send any data packets and we set 

PDR=0. Moreover, we assume that transport layer prohibits 

AOMDV from sending more than 5 unacknowledged packets. 

A Randomly placed wormhole is added to the network. All 

traffics attracted to the wormhole were taken into account for 

different wormhole locations. The simulation is repeated 20 

times. Table 2 shows the simulation results. Note that, in our 

proposed protocol, failure detection and data redirection is 

performed at the network layer, while AOMDV and 

ITAMODV execute one of the tasks (if any) at a higher layer. 



Therefore, as a rule of thumb, our proposed protocol reacts to 

failures faster than AOMDV and its intelligent version, 

ITAOMDV. 

As stated before, discarding only one data packet is enough 

for a misbehavior-aware node, i.e. a node following MTMR 

protocol, to redirect the data stream. On the other hand, if the 

first hop is changed during data redirection, since wormhole 

has advertised a low hop count, the new first hop may try the 

wormhole. Therefore the average data loss for traffics attracted 

to a wormhole is a little higher than 1. The strict data 

redirection property of the MTMR algorithm leads to reliable 

detection of all misbehaving nodes. Noting that in the 

simulation scenarios, there is only one wormhole and since our 

proposed protocol checks all available next hops in case of a 

data packet drop, the data redirection is completely successful. 

(Assuming that wormhole node is not the only neighbor of the 

source). 

Focusing on AOMDV's row we see that, TCP prohibits 

sending data after 5 unsuccessful tries. Therefore, if a traffic is 

attracted to wormhole, packets will be lost and TCP stops the 

traffic after five timeout packets. As a result, PDR would be 

zero and data loss would be the same 5. 

If we consider Intelligent TCP AOMDV, both failure 

detection and data redirection are triggered by TCP. Since 

AOMDV discovers link-disjoint paths, if there is only one 

wormhole present in the network, the second path will not use 

that link and data loss will be 5. But according to figure 3, this 

performance degrades drastically when the number of 

wormholes increases. The reason is that AOMDV at maximum 

finds three link-disjoint paths. Therefore, if three wormhole 

pairs exist near the desired traffic, they will be chosen by 

AOMDV and data redirection fails after ITAOMDV tries all of 

them. On the contrary, since proposed protocol considers all 

existing paths, it has the chance to find a safe route at the 

fourth attempt. 

Proposed 

protocol 

AOMDV 

ITAOMDV 

Table II. Wormhole Detection 

Failure 

Detection 

Data 

Redirection 

Average 

PDR 

Network 

layer 

Transport 

layer 

Transport 

layer 

Network 

layer 

Average 

Data Loss 

0.99867 1.3 

No 0 5 

Transport 

layer 

0.78324 5 

Next, we analyze network average PDR when more than 

one wormhole pair exists in the network. Previously- defined 

random network is analyzed for different number of wormhole 

pairs and random locations. For a specific number of wormhole 

pairs, the results are averaged for 10 different wormhole 

locations and network traffics. Network PDR is illustrated in 

figure 3. It can be seen that ITAOMDV is more resilient to 

wormhole attack than traditional AOMDV. Obviously our 

proposed scheme outperforms both AOMDV versions and 

provides a much better performance against wormhole attacks. 

Figure 4 compares data loss rate of three protocols in case 

of wormhole attack. It can be easily deduced that the proposed 

solution minimizes data loss. For ITAOMDV and AOMDV, 

there is a tradeoff between PDR and data loss. ITAOMDV 

sustains network performance by reducing PDR deprivation, 

but this benefit results in a higher data loss rate compared to 

AOMDV. It can be concluded that the proposed protocol 

outperforms the previous protocols and prohibits misbehaving 

nodes from degrading network performance. 

Network Packet Delivery Ratio 

1 

0.98 

0.96 

0.94 

0.92 

0.9 

0.88 

0.86 

0.84 

0.82 

Figure 3 

Figure 4 

Network PDR in presence of wormhole pairs 

0.8 

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 

Data loss 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

Proposed protocol 

ITAOMDV 

AOMDV 

No. of wormhole pairs 

Data loss in case of wormhole attack 

Proposed protocol 

ITAOMDV 

AOMDV 

0 

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 

No. of wormhole pairs 

C. Performance of Benign nodes 

We utilize the same random network mentioned before 

with 10 traffics initiated randomly between 10 randomly 

selected pairs. Each traffic stream contains 1000 data packets. 

Randomly selected selfish nodes are added to the network. 



Since 20 nodes are selected to participate in benign traffic pairs 

and there are 50 nodes in the network, selfish nodes can be up 

to 60% of network nodes. 

Two attacks are simulated. In the first case, network is 

subject to selfish attack type II, the second shows network 

behavior in the presence of a more complex attack in which 

selfish nodes are of both types. Each attack is simulated 30 

times. 

Figure 5 shows the PDR of the considered traffic streams. It 

is obvious that MTMR prohibits selfish behavior from 

degrading network performance. 

Figure 5 shows that MTMR is more resilient to complex 

attack and outperforms AOMDV in presence of both attacks. 

Selfish nodes are chosen from nodes not included in traffic 

pairs, this clarifies why curves do not reach zero even if all 

remaining nodes are selfish. Some path may solely consist of 

nodes participating in traffic pairs. Therefore, curves ending 

area depends on network topology and the choice of traffic 

pairs. 

As stated before, a type I selfish node reduces number of 

discovered paths. Therefore, as can be seen in figure 5, adding 

selfishness type I results in a better PDR in low selfish node 

density and a worse PDR in high density scenarios. An 

increase in the PDR is due to removing some paths that contain 

selfish node type II as well as selfish node type I. The 

performance degradation is caused by selfish nodes type I 

removing selfish type II-free paths. 

Packet Delivery Ratio considering avoided streams 

1 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

Figure 5 PDR, selfish II & complex attack 

MTMR selfish II attack 

AOMDV selfish II attack 

MTMR complex attack 

AOMDV complex attack 

MTMR versus AOMDV 

0 

0 10 20 30 40 50 60 

% of selfish nodes 

Every security implementation has a cost. The cost for 

detecting and punishing selfishness in addition to keeping 

network performance is higher number of RREP transmissions. 

One of the achieved gains is a significant reduction in data loss; 

number of generated but not received data packets. Number of 

control packet transmissions is shown in figure 6. It can be 

seen that MTMR has higher number of RREP transmissions. 

Figure 7 compares protocols' data loss in case of complex 

attack. 

Figure 6 AOMDV & MTMR (RREQ+RREP) transmissions considering 

complex attack 

No. of (RREQ+RREP) transmissions 

Data loss 

5000 

4500 

4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

1000 


0 

0 10 20 30 40 50 60 

900 

800 

700 

600 

500 

400 

300 

200 

100 


MTMR 

AOMDV 

Figure 7 Data loss, protocols are subject to complex attack 


MTMR 

AOMDV 

0 

0 10 20 30 40 50 60 


Another impact of misbehaving nodes is increasing the 

power consumption of benign nodes. In order to investigate 

the trade off for selfish-aware routing, we compare number of 

sent bits for specified traffics. Sent bytes consist of control 

packets and data retransmissions. IP standard 

recommendations are used as a reference for data packet size. 

This is shown in figure 8. Sent bytes are divided by 100,000 

bytes. 

It is obvious that MTMR outperforms AOMDV in terms of 

sent bytes per traffic. This means reaching the routing security 

goals discussed before does not increase nodes' sent bytes 

when network is subject to selfish attacks. But also decreases 

transmission power loss per traffic. Moreover, simulation 

results demonstrate that in contrast to defenseless protocol, 

MTMR sent bytes do not increase when number of selfish 

nodes increases. The reason is that our defense scheme 

obstructs data loss and control overheads (control packets) 

occupy a considerably smaller amount than data payload. 

Therefore, although MTMR has higher number of control 



packet transmissions, its lower data loss results in a noticeable 

reduction in sent bytes. 

same as the data illustrated in table 2. Simulation results 

confirm this claim. We avoid repetition due to space limits. 

Normalized Sent Bytes 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

Figure 8 Sent bytes considering complex attack 


MTMR 

AOMDV 

0 

0 10 20 30 40 50 60 

D. Punishment 

In this scenario, we use the same network with 10 traffic 

streams that are initiated between 10 randomly selected benign 

pairs. We also include 10 randomly selected selfish nodes. 

Each traffic contains 1000 data packets. Random traffics 

having selfish nodes as source and/or destination are added to 

the network. Each simulation is repeated 30 times to be 

averaging over randomness. 

In order to show punishment property of MTMR, we define 

the benchmark "Selfish Attempt Success Ratio" as the ratio of 

successful data deliveries to the number of tries to send the 

packets. This is effectively equal to the ratio of received ACK 

packets to the initiated data packets for selfish nodes. The 

lower the SASR, the lower the chance for selfish nodes to have 

a successful data connection and therefore, the more severe the 

punishment. Figure 9 compares SASR in MTMR and AOMDV 

protocols. It can be easily concluded that MTMR significantly 

punishes selfish nodes. 

In a network with selfish nodes, it is desirable to have a 

higher PDR for benign nodes compared to selfish nodes. 

Therefore, we can consider "Benign to Selfish PDR" as a point 

of reference showing punishment of selfish nodes. Figure 10 

shows the value of this benchmark in both protocols as 

percentage of selfish nodes increases. It can clearly be seen 

that MTMR performs better than AOMDV. 

E. Sinkhole and Grey-hole 


Noting the definitions, from the perspective of a MTMR 

node, a selfish node type II, a sinkhole, a grey-hole and a 

wormhole node all represent the same behavior. They forward 

routing packets but discard data packets. Therefore, all these 

misbehaviors will face the same reaction by benign nodes. 

Hence, simulation results for all these cases will be the same. 

Namely, they will all be punished according to the same 

curve, and sinkhole and grey-hole detection will be about the 

Selfish Attempt Success Ratio 

Benign to Selfish PDR 

1 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

Figure 9 Selfish nodes Attempt Success Ratio 

0 

0 2 4 6 8 10 12 14 16 18 20 

Figure 10 MTMR versus AOMDV, Benign to Selfish PDR 

6 

5 

4 

3 

2 

1 

MTMR 

AOMDV 


Number of selfish connections 


Acknowledgment 

This work is partially supported by Cryptographic Chair of 

Iran National Science Foundation (INSF) under contract No. 

84/5193 and Iran Telecommunication Research Center (ITRC) 

under contract No. T/500/20961 in Information Systems and 

Security Lab (ISSL) Electrical Engineering Department of 

Sharif University of Technology. 

VI. REFERENCES 

AOMDV 

MTMR 

0 

0 10 20 30 40 50 60 


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Short Biography with photograph 

Hanie Sedghi received her B.Sc. and M.Sc. in Electrical Engineering from Sharif University of Technology in 2007 and 2009 

respectively. She is currently a PhD Student in Electrical Engineering Department University of Southern California. Her 

research interests include Network optimization, wireless networks and Learning in networks. 

Mohammad Reza Pakravan received his B.Sc. in Electrical Engineering from Tehran University. He received is M.Sc. and 

his PhD from university of Ottawa. He is currently Associate professor at Sharif University of Technology. His research 

interests are Data Networking Protocols, Optical Communications, Cooperative Communications, Cognitive Radio 

Systems, Cross Layer Optimization, Wireless Ad Hoc and Sensor Networks. 

Mohammad Reza Aref received a bachelor's degree in electronics engineering from the University of Tehran, and the 

master's and Ph.D. degrees in electrical and communication engineering from Stanford University in 1975, 1976 and 1980, 

respectively. His PhD dissertation was on the information theory of networks, supervised by Prof. Thomas M. Cover. He 

introduced and analyzed deterministic relay networks which is later termed by Aref Networks. He is currently professor in 

electrical engineering department, Sharif University of Technology. His research interests are Information Theory and 

Security.

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