Efficient Packet Transmission in Wireless Ad Hoc Network

Efficient Packet Transmission in Wireless Ad Hoc Network

1. Sujatha M.E., / Assistant Professor, Computer Science and Engineering,

   M.Kumarasamy College of Engineering, Karur, India.

2. Sundar Selvakumar/ M.E Scholar, Computer Science and Engineering,

1. umarasamy College of Engineering, Karur, India.

   Abstract Wireless ad hoc network is a network formed without any central infrastructure which consists of nodes that use a wireless interface to send packet data. Linkage error and malicious packet dropping are two sources for packet losses in wireless ad hoc network. A sequence of packet losses are present in the network, it determines whether the losses are caused by linkage errors only, or by the joint effect of linkage errors and malicious drop. In the interior-attack case, whereby malicious nodes that are part of the route utilize their knowledge of the communication framework to selectively drop a small amount of packets vital to the network performance. This is because the packet dropping rate is comparable to the channel error. Conventional algorithms are used to detect the packet loss rate that cannot reach acceptable detection accuracy. We proposed to improve the detection accuracy. So we developed the correlations between lost packets and to ensure truthful calculation of these correlations, the homomorphic linear authenticator (HLA) is used. HLA is based on public auditing architecture that allows the detector to verify the truthfulness of the packet loss information reported by nodes. This development is privacy protect, scam proof, and low communication and storage overheads. It reduce the computation overhead, a packet-block based method is also included, which allow to trade detection truthfulness for lower computation complexity. The proposed mechanisms obtain much better detection accuracy than conventional methods.

   Index TermsWireless Ad hoc Network, Public Auditing, Selective Dropping, Homomorphic Linear Authenticator

   1. INTRODUCTION

      Wireless ad hoc networks are collections of wireless nodes that communicate directly over common wireless channel. The nodes are equipped with wireless transceiver. They dont need any additional infrastructure, such as base station or wired access point, etc. Therefore, each node doesnt only plays the role of an end system, but also acts as a router, that sends packets to desired nodes. The ad hoc are expected to do assignments, which the infrastructure cant do. Ad hoc networks are mostly used by military, rescue mission team. Their works cant rely on a infrastructures network. As an illustrative example, imagine fire fighters put out hazardous fire in a big forest. They have to communicate each other, but establishing a infrastructure or cabling in such area is impossible or too expensive. The main problems in ad hoc networks are routing and characteristic of wireless communication. In infrastructures networks a node can communicate with all nodes in the same cell. In ad hoc a node can communicate only with nodes in its area, this node

      can communicate with other nodes, but a routing algorithm is necessary. Unlike wired communication, wireless networks have transmission problem with data transmission such as, possibility of asymmetric connections and higher interferences. The aim of this overview article is to provide informations on ad hoc networks and specially WANET, their structure, their applications on the current time, as well as their strong and weakness in comparison with infrastructure networks.

      In the case of computer networks, the ad hoc networks mean wireless network without infrastructure, they can be called spontaneous network. One way to understand ad hoc network is by comparing them with infrastructure based wireless networks, such as cellular network and WLAN. In the infrastructure based wireless networks a node can only send a packet to a destination node only via access point (in cellular network like GSM, it is called base station). The access point establishes an network area and only the nodes in this area can use access points services. There are some unknown events, which cause access points malfunction. The nodes lose their network and they are quasi not working. It is the biggest infrastructures disadvantage. There are also some reasons to sacrifice or not to use access points services. These can be cost factor, impossibility to install access point in short time, etc. In this case the nodes have to build its own network. This network is called wireless ad hoc network. The wireless ad hoc networks only consist of nodes equipped with transceiver. The network is created to be independent from an infrastructure. Therefore, the nodes must be able to arrange their own networks. A node can now communicate only with other nodes in its transmission range. In the infrastructure based wireless network, the nodes can communicate with a node, which is located in another network area, by transmitting data to destination access point and this access point relay the data to the desired node. It seems like, that the ad hoc networks are not powerful enough. Each node has its own transmission range, if these small transmission areas are combined, they will form a much bigger transmission area. The nodes transmit their data with single or multiple hopping techniques. Now a suitable routing algorithm must be implemented, so the process of transmitting data will be more effective.

      Fig. 1. IEEE 802.11

      The wireless networks can be categorized based on their system architecture into two basic versions. The one is Infrastructure and second is ad-hoc network. The biggest difference in them is infrastructure networks consist of access point and nodes, meanwhile the ad hoc networks are independent from access point. In the infrastructure version, a terminal cant communicate directly with other terminals in the same cell and other cell. A access point here perform control messages. Messages are sent to the access point and then the access point distributes the messages to the desired terminal. If a terminal wants to communicate with a terminal, which is located in other cell, the access point will relay the message to other access point, which has control over desired cell. The access points are normally wired connected. The problem in infrastructure, if the access point fails, all terminals in this cell cant perform any communication. Unlike the infrastructure, the ad hoc networks have a different method to distribute messages. In a given network, N1 want to communicate with N5. N5 is located outside N1 transmission range, so N1 must hop the message to N4-N2- N3-N5 or N2-N3-N5. Routing algorithm will decide which route performs the best. There will be no problem if N4 leaves the network, because N1 still has a route to N5. Therefore ad hoc networks are robuster than infrastructure.

      Fig. 2. Transmission area in ad hoc

      A. Public auditing

      The public auditor should not be able to decern the content of a packet delivered on the route through the auditing information submitted by individual hops, no matter how many independent reports of the auditing information are submitted to the auditor. Second, our construction incurs low communication and storage overheads at intermediate nodes. At last, to significantly reduce the computation overhead of the baseline constructions so that they can be used in computation-constrained mobile devices, a conventional- based algorithm to achieves scalable signature generation and detection. This mechanism allows one to trade detection accuracy for lower computation complexity.

      A malicious node tht is occurred on the route can exploit its information of the network protocol and the communication context to launch an insider attackan attack that is intermittent, but can achieve the network performance degradation. Detecting selective packet-dropping attacks is extremely challenging in a highly dynamic wireless environment. The difficulty comes from the requirement that we need to not only detect the place (or hop) where the packet is dropped, but also identify whether the drop is intentional or unintentional. (e.g., fading, noise, and interference, a.k.a., link errors), or by the insider attacker.

      The above problem has not been well addressed in the literature. The most of the related works preclude the ambiguity of the environment by assuming that malicious dropping is the only source of packet loss, so that there is no need to account for the impact of link errors. On the other hand, for the small number of works that differentiate between link errors and malicious packet drops, their detection algorithms usually require the number of maliciously-dropped packets to be significantly higher than link errors, in order to achieve acceptable detection accuracy.

   2. LITERATURE SURVEY

Tao Shu and Marwan Krunz, Privacy-Preserving and Truthful Detection of Packet Dropping Attacks in Wireless Ad Hoc Networks [14], In a multi-hop wireless network, nodes cooperate in relaying or routing traffic. An adversary can exploit this cooperative nature to launch attacks. For example, the adversary may first pretend to be a cooperative node in the route discovery process. Once being included in a route, the adversary starts dropping packets. In the most severe form, the malicious node simply stops forwarding every packet received from upstream nodes, completely disrupting the path between the source and the destination. Eventually, such a severe Denial-of-Service (DoS) attack can paralyze the network by partitioning its topology. Even though persistent packet dropping can effectively degrade the performance of the network, from the attackers standpoint such an always-on attack has its disadvantages. First, the continuous presence of extremely high packet loss rate at the malicious nodes makes this type of attack easy to be detected. Second, once being detected, these attacks are easy to mitigate.

Link error and malicious packet dropping are two sources for packet losses in multi-hop wireless ad hoc network. In

determining whether the losses are caused by link errors only, or by the combined effect of link errors and malicious drop. We are especially interested in the insider-attack case, whereby malicious nodes that are part of the route exploit their knowledge of the communication context to selectively drop a small amount of packets critical to the network performance. Because the packet dropping rate in this case is comparable to the channel error rate, conventional algorithms that are based on detecting the packet loss rate can achieve satisfactory detection accuracy.

S.Amutha, K.Balasubramanian, Secure Implementation of Routing Protocols for Wireless Ad hoc Networks [10], Routing is a fundamental networking function in every communication system including wireless Ad hoc networks. Attacks on ad hoc network routing protocols disrupt network performance and reliability. In addition intermediate nodes can be corrupted and thus exhibit arbitrary behavior. Route discovery messages are protected by pair wise secret keys between a source and destination. The performance of secure implementation of the existing routing protocols can be compared with Dynamic Source Routing (DSR) and Ad hoc On-demand Distance Vector (AODV).It is difficult to keep addresses on each nodes.

T.Shu, M.Krunz and S.Liu, Secure Data Collection in Wireless Sensor Networks Using Randomized Dispersive Routes [10], To overcome the black holes that are formed due to compromised-node (CN) and denial-of-service (DOS) by using some routing mechanisms. Basic idea of developing this paper is nothing but combat the vulnerability of existing system in handling such attacks due to their deterministic nature i.e., once an obstructionist can gather or acquire the routing algorithm can figure out the same routes known to the source, and hence intimidate all information sent over these routes. A randomized multi-path routing algorithm that can overcome the black holes formed by Compromised-node and denial-of-service attacks. It is to compute multiple paths in a randomized way each time an information packet needs to be sent, such that the set of routes taken by various shares of different packets keep changing over time. the packet is no longer forwarded is considered a suspect for misbehaving because of random routing

A.Proano and L.Lazos, Packet-Hiding Methods for Preventing Selective Jamming Attacks [11], Denial-of- Service attacks on wireless networks. Typically, jamming has been addressed under an external threat model. However, adversaries with internal knowledge of protocol specifications and network secrets can launch low-effort jamming attacks that are difficult to detect and counter. In this work, address the problem of selective jamming attacks in wireless networks. In these attacks, the adversary is active only for a short period of time, selectively targeting messages of high importance. To illustrate the advantages of selective jamming in terms of network performance degradation and adversary effort by presenting two case studies; a selective attack on TCP and one on routing. The selective jamming attacks can be launched by performing real-time packet classification at the physical layer. To mitigate these attacks,

its to develop three schemes that prevent real-time packet classification by combining cryptographic primitives with physical-layer attributes. To analyze the security of the methods and evaluate their computational and communication overhead are little bit highly complex.

. III. DESCRIPTION OF THE SYSTEM

1. System Model

   A random path in a multi-hop wireless ad hoc network, as shown in Figure 3. The source node S send packets to the destination node D through intermediate nodes n1, . . . , nK. The source node S is aware of the route PSD, as in Dynamic Source Routing otherwise it performing a trace route operation. The network topology and link characteristics remain unchanged for a quite long period of time. It focus on static wireless ad hoc network. A sequences of M packets are transmitted simultaneously over the channel to the receiver obtains an awareness of the channel state (a1. . . aM ), where aj as 1 denotes the packet was successfully received, and 0 denotes the packet was dropped. fc(i) is derived by computing the autocorrelation function.

   Fig. 3. Network and Attack Model

2. Proposed Detection Scheme

   The proposed mechanism is based on detecting the correlations between the lost packets over each hop of the path. The basic idea is to model the packet loss process of a hop as a random process alternating between 0 (loss) and 1 (no loss). Specifically, consider that a sequence of M packets that are transmitted consecutively over a wireless channel. By observing whether the transmissions are successful or not, the receiver of the hop obtains a bitmap (a1, . . . , aM ), where aj 2 f0, 1g for packets j = 1, . . . , M. The correlation of the lost packet is calculated as the auto-correlation function of this bitmap. Under different packet dropping conditions, i.e., link- error vs. malicious dropping, the instantiations of the packet- loss random process should present distinct dropping patterns (represented by the correlation of the instance). This is true even when the packet loss rate is similar in each instantiation. To verify this property, in Figure 2 we have simulated the auto-correlation functions of two packet loss processes, one caused by 10% link errors, and the other by 10% link errors

   plus 10% malicious uniformly-random packet dropping. It can be observed that significant gap exiss between these two auto-correlation functions. Therefore, by comparing the auto- correlation function of the observed packet loss process with that of a normal wireless channel (i.e., fc(i)), one can accurately identify the cause of the packet drops.

   The benefit of exploiting the correlation of lost packets can be better illustrated by examining the insufficiency of the conventional method that relies only on the distribution of the number of lost packets. More specifically, under the conventional method, malicious-node detection is modeled as a binary hypothesis test, where H0 is the hypothesis that there is no malicious node in a given link (all packet losses are due to link errors) and H1 denotes there is a malicious node in the given link (packet losses are due to both link errors and malicious drops). Let z be the observed number of lost packets on the link during some interval t. Then,

   x, under H0 (no malicious nodes)

   z ={

   x + y, under H1 (there is a malicious node)

   Where x and y are the numbers of lost packets caused by link errors and by malicious drops, respectively. Both x and y are random variables.

3. Audit Phase

   This phase is triggered when the public auditor Ad receives an ADR message from S. The ADR message includes the id of the nodes on PSD, ordered in the downstream direction, i.e., n1, . . . , nK , Ss HLA public key information pk = (v, g, u), the sequence numbers of the most recent M packets sent by S, and the sequence numbers of the subset of these M packets that were received by D. Recall that we assume the information sent by S and D is truthful, because detecting attacks is in their interest. Ad conducts the auditing process. Note that the above mechanism only guarantees that a node cannot understate its packet loss, i.e., it cannot claim the reception of a packet that it actually did not receive. This mechanism cannot prevent a node from overly stating its packet loss by claiming that it did not receive a packet that it actually received. This latter case is prevented by another mechanism discussed in the detection phase.

   Fig. 4. Comparison of Correlation of lost packets

4. Detection Phase

The public auditor Ad enters the detection phase after receiving and auditing the reply to its challenge from all nodes on PSD. The main tasks of Ad in this phase include the following: detecting any overstatement of packet loss at each node, constructing a packet-loss bitmap for each hop, calculating the autocorrelation function for the packet loss on each hop, and deciding whether malicious behavior is present. More specifically, Ad performs these tasks as follows. The auditor calculates the autocorrelation function.

The detection process applies to one end-to-end path. The detection for multiple paths can be performed as multiple independent detections, one for each path. Although the optimal error threshold that minimizes the detection error is still an open problem, our simulations show that through trial-and-error, one can easily find a good th that provides a better detection accuracy than the optimal detection scheme that utilizes only the pad of the number of lost packets.

IV.PERFORMANCE EVALUATION

Simulation Setup

The detection accuracy which can be achieved by the Conventional algorithm with the optimal maximum likelihood algorithm that utilizes the distribution of the number of lost packets. For given packet-loss bitmaps, the detection on different hops is conducted separately. So, only need to simulate the detection of one hop to evaluate the performance of a given algorithm. It assume packets are transmitted continuously over this hop, i.e., a saturated traffic environment and assume channel fluctuations for this hop follow the Gilbert-Elliot model, with the transition probabilities from good to bad and from bad to good given respectively. The two types of malicious packet dropping: random dropping and selective dropping. In the random dropping attack, a packet is dropped at the malicious node with probability. In the selective dropping attack, the adversary drops packets of certain sequence numbers.

Selective Packet Dropping

The detection error as a function of the number of maliciously dropped packets. Similar performance trends can be observed to the case of the random packet dropping. Fewer detection errors are made by both algorithms when more packets are maliciously dropped. In all the simulated cases, the proposed algorithm can detect the actual cause of the packet drop more accurately than the ML scheme, especially when the number of maliciously dropped packets is small. When the number of maliciously dropped packets is significantly higher than that caused by link errors (greater than 4 packets in our simulation), the two algorithms achieve comparable detection accuracy. In this scenario, it may be wise to use the conventional ML scheme due to its simplicity (e.g., no need to enforce truthful reports from intermediate nodes, etc).

Dropping of Control Packets

The simulations so far have not made any application- semantic (use case) assumption on the dropped packets. In reality, however, because these packets are usually used for control purposes, the loss of these packets may generate significant impacts on the transmission of other (i.e., data) packets. In this series of simulations, to evaluate how the correlation between the control and data packets affects the performance of the proposed scheme. In particular, consider a multi-hop cognitive radio network, where control packets are exchanged over an end-to-end path to maintain channel synchronization between consecutive hops.

Block-Based Detection

In this series of simulations, the detection accuracy of block-based algorithms as a function of block size. In general, it shows that for both cases the detection error increases with the block size. This is expected, as a larger block size hides more details of packet losses, and therefore makes the actual correlation of lost packets more difficult to calculate. Meanwhile, the benefit of blocked-based algorithm is also observed. It is able to trade computation complexity for better detection accuracy.

Fig. 5. Detection accuracy of block-based algorithms

VI. CONCLUSION

An accurate method for detecting selective packet drops made by insider attackers is proposed in this paper. It also provides a truthful and publicly verifiable decision statistics as a proof to support the detection decision. The high detection accuracy is achieved by exploiting the correlations between the positions of lost packets, as calculated from the auto-correlation function (ACF) of the packet-loss bitmapa bitmap describing the lost/received status of each packet in a sequence of consecutive packet transmissions. The basic idea behind this method is that even though malicious dropping may result in a packet loss rate that is comparable to normal channel losses, the stochastic processes that characterize the two phenomena exhibit different correlation structures (equivalently, different patterns of packet losses). Therefore, by detecting the correlations between lost packets, one can decide whether the packet loss is purely due to regular link errors, or is a combined effect of link error and malicious drop. The algorithm takes into account the cross-statistics between lost packets to make a more informative decision, and thus is in sharp contrast to the conventional methods that rely only on the distribution of the number of lost packets. It is compared with conventional detection algorithms that utilize only the distribution of the number of lost packets, exploiting the correlation between lost packets significantly improves the accuracy in detecting malicious packet drops.

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