A SURVEY ON SECURITY, ENERGY & CONGESTION BASED ISSUES IN MULTIPATH ROUTING FOR WIRELESS SENSOR NETWORK.

A SURVEY ON SECURITY, ENERGY & CONGESTION BASED ISSUES IN MULTIPATH ROUTING FOR WIRELESS SENSOR NETWORK. A Thesis submitted toward partial fulfillment Of the requirements for the degree of Master in Multimedia Development Course affiliated to Faculty of Engineering & technology Jadavpur University Submitted By SARENDRILA BAL Examination Roll Number: M4MMD14-18 Under the Guidance of Mrs. Saswati Mukherjee Jadavpur University School of Education Technology Master in Multimedia Development Faculty of Engineering and Technology Jadavpur University Kolkata-700032 India 2014 I

Master in Multimedia Development course affiliated to Faculty of Engineering & Technology Jadavpur University, Kolkata, India CERTIFICATE OF RECOMMENDATION This is to certify that the thesis entitled A SURVEY ON SECURITY, ENERGY & CONGESTION BASED ISSUES IN MULTIPATH ROUTING FOR WIRELESS SENSOR NETWORK is a bonafide work carried out by SARENDRILA BAL under our supervision and guidance for partial fulfilment of the requirement for Post Graduate Degree of Master in Multimedia Development during the academic session 2013-2014. ------------------------------------- THESIS ADVISOR Mrs. Saswati Mukherjee, Assistant Professor School of Education Technology, Jadavpur University, Kolkata-700 032 ------------------------------------- DIRECTOR School of Education Technology, Jadavpur University, Kolkata-700 032 ------------------------------------ DEAN Faculty Council of Interdisciplinary Studies, Law and Management, Jadavpur University, Kolkata-700 032 II

Master in Multimedia Development course affiliated to Faculty of Engineering & Technology Jadavpur University, Kolkata, India CERTIFICATE OF APPROVAL** This foregoing thesis is hereby approved as a credible study of an engineering subject carried out and presented in a manner satisfactorily to warranty its acceptance as a prerequisite to the degree for which it has been submitted. It is understood that by this approval the undersigned do not endorse or approve any statement made or opinion expressed or conclusion drawn therein but approve the thesis only for purpose for which it has been submitted. Committee of final examination ----------------------------------------------- For evaluation of Thesis ----------------------------------------------- ----------------------------------------------- ----------------------------------------------- ** Only in case the thesis is approved. III

DECLARATION OF ORIGINALITY AND COMPLIANCE OF ACADEMIC ETHICS I hereby declare that this thesis contains literature survey and original research work by the undersigned candidate, as part of her Master of Multimedia Development in engineering studies during academic session 2013-2014. All information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by this rules and conduct, I have fully cited and referred all material and results that are not original to this work. NAME : SARENDRILA BAL EXAM ROLL NUMBER: M4MMD14-18 THESIS TITLE : A SURVEY ON SECURITY, ENERGY & CONGESTION BASED ISSUES IN MULTIPATH ROUTING FOR WIRELESS SENSOR NETWORK. SIGNATURE : DATE: IV

ACKNOWLEDGEMENT I would like to express my deep sense of profound gratitude to my honorable, esteemed guide, Mrs. Saswati Mukherjee for her guidance and constant support had helped me understand the subject and achieve results. I am glad to work under her supervision. I extend my thanks to our Director Prof. Samar Bhattacharya and all respected Faculties of our Department for their valuable advices and support. Also I would like to thanks Almighty, my family and friends for their constant support, love and encouragement. Date: Place: Sarendrila Bal Examination Roll: M4MMD14-18 Class Roll: 001230401023 University Registration No: 121337 of 2012-13 School of Education Technology Master in Multimedia Development V

Executive Summary A wireless sensor network (WSN) is a large collection of sensor nodes with limited power supply and constrained computational capability. Due to the restricted communication range and high density of sensor nodes, packet forwarding in sensor networks is usually performed through multi-hop data transmission. Therefore, routing in wireless sensor networks has been considered an important field of research over the past decade. There is no infrastructure, so wireless links are unreliable, susceptible to various attacks and have to meet strict energy saving and load balancing. The present work gives a detailed overview of the problems of multipath routing in terms of security, Energy efficiency and congestion control as they are the three main challenging issues of WSN. With this in mind the major defensive, Secure, Energy Efficient and Load Balanced measures are described for these problems and analyze them vividly. VI

Contents 1. Introduction...1 1.1 Problem statement...1 1.2 Objectives...1 1.3 Assumptions...1 1.4 Background Concepts...2 1.5 Literature survey...4 1.6 Outline of Thesis...6 2 Concepts and problem analysis...7 3Design/Methodologies...11 4 Results and Interpretations...33 5 Conclusions and Future Scope...36 6 References...37 VII

1. INTRODUCTION Recent technological advances allow us to envision a future where large numbers of low power, inexpensive sensor devices are densely embedded in the physical environment, operating together in a wireless network [1]. The envisioned applications of these wireless sensor networks range widely. Wireless sensor network s (WSN)[3] application can be categorized as following:1)event Detection and Reporting, refer to intruder detection systems in military or detecting unusual behavior or failures in a manufacturin g process or detection of forest fires. 2) Data Gathering and Periodic Reporting is Monitoring temperature, humidity and lighting in office buildings can be placed in this category. 3) Sink-initiated Querying, is where sensors gather data and report to sink as it commands.4) Tracking-based Applications serves where military or border surveillance tracks an intruder or the movements of a shady object is interesting.5) Environmental applications include tracking the movements and patterns of insects, birds or small animals. 1.1 PROBLEM STATEMENT A Review on Security, Energy & Congestion based issues in multipath routing for Wireless Sensor Network. 1.2 OBJECTIVE The objectives are stated below: Study new approaches taken in wireless sensor networks that provide secure, energy aware, congestion control concept. To focus on advantages and future scope of the mentioned algorithms. 1.3 ASSUMPTIONS The multipath routing protocols has been assumed in this work to improve performance, reliability, load balancing and QoS improvement. Three most challenging and explored areas such as Security, Energy efficient and congestion control techniques have been assumed here. 1

1.4 BACKGROUND In WSN [8], each spatially distributed sensor node communicates with each other to forward their sensed information to a central processing unit/sink or carry out some local coordination. The sensor nodes either form a flat network topology where sensor nodes also act as routers and transfer data to a sink through multihop routing, or a hierarchical network topology where more powerful fixed or mobile relays are used to collect and route the sensor data to a sink. The ideal wireless sensor network is alleged to be scalable, fault tolerance, little power consumption, smart and software programmable, efficient, competent of fast data acquisition, reliable and accurate over long term, low cost and required no real maintenance. DESIGN CHALLENGES: This section lists down the main aspects involved in the design challenges in wireless sensor networks [7]: Limited Energy Capacity Energy poses a big challenge for the network designers since sensor nodes are Battery powered, they have limited energy capacity. Consequently the routing protocols designed for sensors should be as energy efficient as possible to extend their lifetime. Coverage A sensor's view of the environment is limited both in range and in accuracy it can only cover a limited physical Area of the environment. Hence, area coverage is also an important design parameter in WSNs. Limited Hardware Resources Sensors can perform only limited computational functionalities due to their limited processing and storage capacities. These hardware constraints present many challenges in software development and network protocol design for sensor networks. Node Deployment Topological deployment of the sensors in WSNs is application dependent and finally affects the performance of the routing protocol. The sensors nodes are scattered randomly create an infrastructure in an ad hoc manner. In that infrastructure, the position of the sink or the cluster-head is also crucial in terms of energy efficiency and performance. 2

Network Characteristics and Unreliable Environment The WSN is prone to frequent topology changes because it is extremely vulnerable to node failure, sensors addition, deletion, node damage, link failure, sensor energy exhaustion etc. So the network routing protocol must be capable of sustain the network topology dynamics, increase network size, energy consumption level, sensor nodes mobility Data Aggregation In WSN the redundancy of data generated from sensor nodes is a key concern. Similar packets from multiple nodes can be aggregated to reduce the extra overhead due to number of the transmissions. Many proposed routing protocols are using data aggregation technique to achieve energy efficiency and data transfer optimization. Fault Tolerance If many nodes fail, routing protocols must accommodate formation of new links and routes to the base stations. This may require actively adjusting transmit powers and signaling rates on the existing links to reduce energy consumption, or rerouting packets through regions of the network where more energy is available. Scalability Scalability is important in WSN as the network size can grow rapidly. So the routing protocols should be designed to work consistently, keeping in consideration that sensors may not necessarily have the same capabilities in terms of energy, processing, sensing, and particularly communication. Quality of Service (Qos): In some applications, data should be delivered within a certain period of time from the moment it is sensed otherwise the data will be useless. Therefore bounded latency for data delivery is another condition for time constrained applications. 3

1.5 LITERATURE SURVEY Here some papers related to the present work given here: Yunfeng Chen et. al, proposed a routing protocol [9] which describe the security feature by the unique way that it selects the routing path between the source and sink node, i.e., the path is selected by the base station instead of the source or sink node. This feature determines that it can defend specifically against attacks on routing protocols that attract traffic by advertising high quality route to the base station. Suraj kumar et.al, proposed a secure cluster based multipath routing protocol [11] which is same as above but adds the concept of clustering.it uses a digitally singed certificate so that, no adversary can create a forge ID. Any node who wants to send a message to the base station will encrypt it and create a MAC with the unique shared key, so that only BS can access it and, any adversary can t perform eavesdropping or altering to the message.bs before actually using the pairwise key both nodes can authenticate each other in this way if any fake node using the ID and certificate of other node, will not be able to use pairwise key. Mariam et.al, proposed a secure and reliable multipath routing protocol [13] for wsn which consists of three components as On Demand multipath routing-it establishes route only when required.this has the advantage of reducing the routing overhead compared to proactive approaches and thus enhancing the reliability and security. Enhanced Passive acknowledgement is based on passively listening to traffic to analyze the security behavior of neighbors and reduce the routing overhead. Erasure coding is used to enhance the security and reliability while maintaining a low routing overhead. R.Sangeetha et.al, proposed a protocol [20] where node disjoint multiple paths are selected for data transmission to spread the load among different nodes. To provide security digital signature based cryptographic system is used with the RSA algorithm and MD5 hash function. It protocol provides reliability by avoiding the network holes through load balancing and effective multipath selection based on the primary path. This also provides energy efficiency through multipath routing and transmission range adjustment of the nodes in the paths. Lu and Wong proposed a load balancing algorithm [26] to distribute the traffic over the multiple paths discovered. The load balancing algorithm allows the sink node to allocate traffic over multiple paths found based on their cost, which depends on the energy levels and the hop distances of nodes along each path. Bashir Yahya et.al proposed [27] a robust and energy efficient multipath routing protocol. It uses the residual energy, node available buffer size, and Signal-to-Noise Ratio (SNR) to predict the best next hop through the paths construction phase. It examines two methods of traffic allocation 4

the first method uses a single path among the discovered paths to transfer the data message, when this path cost falls below a certain threshold, it then switches to the next alternative path. The second method is to split up the transmitted message into number of segments of equal size, error correction codes, and then transmit it across multiple paths simultaneously to increase the probability that an essential portion of the packet is received at the destination without incurring excessive delay. Jayashree et. al, proposed a reliable energy efficient multipath protocol[29] routing scheme for multimedia traffic. The proposed protocol quickly chooses partial disjoint paths in case of node failure to minimize routing overhead. Hence increases the reliability of the packets reaching the destination with minimum delay. Samira yessad et. al, proposed a protocol [30] which chooses one route among several routes with a probability which will count the residual energy, the energy of communication and the number of paths including the forwarding nodes. It allows the sensor nodes of the network wasting their energy in an equitable manner in order to enhance the lifetime of the sensor network. Moufida Maimour et. al, proposed a protocol [35] described along with the load repartition strategies for congestion control. The load repartition strategies distributes the traffic uniformly on available paths simultaneously.on reception of Congestion Notification from congested nodes a source will try to balance its traffic on available paths in order to keep its sending rate unchanged while reducing the amount of data sent on the current active paths. Omar Banimelhem et. al, proposed [36] a new grid-based multipath routing protocol intended to route packets fast, utilize and extend sensor nodes energy in addition to avoiding and handling network congestion. Inside each grid, one of the sensor nodes is selected as a master node which is responsible for delivering the data generated by any node in that grid and for routing the data received from other master nodes in the neighbor grids. Two congestion control schemes have been proposed i.e., Short term and long term congestions. Cherian et. al, proposed a multipath routing algorithm [37] which enables the reliable delivery of data. By controlling the scheduling rate, congestion and packet loss are prevented. The algorithm provides an efficient way to prevent the packet loss at each node, which results in congestion management in the sensor networks. This protocol prevents packet clustering and provides smoothness to the traffic. Through monitoring and controlling the scheduling rate the flow control and congestion control are managed. M.Usha et. al, proposed protocol [38] which is based on priority to control congestion for heterogeneous traffic in multipath wireless sensor network. It allocates bandwidth proportional to 5

the priority of many applications simultaneously running in the sensor nodes. The parent node of each sensor node allocates bandwidth based on the source traffic priority and transit traffic priority of data from heterogeneous application in the child nodes. Congestion is detected based on the packet service ratio and congestion notification is implicit. 1.6 OUTLINE OF THESIS The rest of the thesis is organized as follows: Section 2 describes the overall concept and analysis of the problem routing in wireless sensor networks. Section 3 describes the methodologies/design to cope with the problem of security, energy, congestion in multipath routing protocol in wireless sensor networks. Section 4 describes the interpretation/result obtained from solutions of the problems. Section 5 concludes the thesis work. It also shows how the future can be conducted. Section 6 contains references of the thesis work. 6

2. CONCEPT AND PROBLEM ANALYSIS The single path routing strategy [1] selects a single path which can be used for transmitting its traffic towards the sink node. Although route discovery through single path routing approach can be performed with minimum computational complexity and resource utilization, the limited capacity of a single path highly reduces the achievable network throughput. In order to cope with the limitations of single path routing techniques, another type of routing strategy, which is called the Multipath routing approach has become as a promising technique in wireless sensor networks which enables to construct several paths from individual sensor nodes towards the destination which can be utilized concurrently. Alternatively, each source node can use only one path for data transmission and switch to another path upon node or link failures. The latter one is mainly used for fault-tolerance purposes, and this is known as alternative path routing. Motivations for Using Multipath Routing Approach in Wireless Sensor Networks Reliability and Fault Tolerance The original idea behind using multipath routing approach in wireless sensor networks was to provide path resilience and reliable data transmission. In the fault tolerance domain, whenever a sensor node cannot forward its data packets towards the sink, it can benefit from the availability of alternative paths to salvage its data packets from node or link failures. Load Balancing and Bandwidth Aggregation According to the resource limitations of wireless sensor nodes, intensive traffic loads in high data rate applications are prone to congestion, which highly influences the network performance. To handle this problem, multipath routing approaches can provide the best solution to support the bandwidth requirements of different applications and reduce the probability of network congestion through splitting network traffic over several paths. QoS Improvement QoS support in terms of network throughput, end-to-end latency and data delivery ratio is an important objective in designing multipath routing protocols for different types of networks. Discovered paths with various characteristics can be utilized to distribute network traffic based on the QoS demands of the application for which the multipath routing protocol has been designed. 7

SECURITY ISSUES IN WIRELESS SENSOR NETWORKS Limited resources such as limited energy, computation and communicational capabilities make WSN susceptible to a variety of attacks including node capture, physical tampering and denial of service [2]. Second, sensor nodes are deployed in accessible areas, have risk of physical attack. Sensor networks [6] interact closely with their physical environments and with people, posing new security problems. Thus Security will be critical concern in WSN s and achieving security is a challenging task. ENERGY EFFICIENCY ISSUES IN WIRELESS SENSOR NETWORKS Data Collision: Data packets [21],[22]collide when a node receives more than one at the same time resulting in all the packets that caused this collision being discarded which will in turn necessitate retransmission of the discarded packets causing significant energy waste. Data Overhearing: Although a node is not transmitting, it will eventually listen to transmissions destined for other nodes causing continuous energy waste. Idle Listening: This phenomenon occurs when a node keeps listening to an idle channel in search of a data packet destined for it, thus wasting a good amount of energy. Interference: Energy is wasted as each node within the transmission and interference range receives a packet but cannot decode it. Control Packet Overhead: Control packets usually synchronize the whole data transmission phase but don't carry any user data. Therefore, it is always a design goal that minimal number of control packets be generated to reduce the energy consumption by these non-data packets. Further, higher security levels in WSNs correspond to more energy consumption for cryptographic functions. So the critical concern is how to reduce the energy consumption of nodes so that the network lifetime can be extended to reasonable times. Energy parameters [23],[24] required during the design of the sensor network: I) The Operational Energy consumption parameter which refers to the energy that a sensor consumes during some specific time of operation and it basically depends on the operation mode of the sensor. 8

II) The Communication Energy parameter refers to the energy consumption due to communication between simple sensors and cluster heads which depends on the distance between the sensors and their cluster head, in each cluster. III) The Battery Capacity Penalty parameter is an important issue in WSNs is self-preservation of the network itself, that is, the maximization of life of network s elements, i.e. the sensors IV) Energy per Packet is referred to the amount of the energy that is spent while sending a packet from a source to a destination. V) Network Lifetime corresponds to the time when the first node exhausts its energy, or when a certain fraction of the network s nodes is dead, or even when all nodes are dead. CONGESTION BASED ISSUES IN WIRELESS SENSOR NETWORKS Congestion occurs in Wireless Sensor Networks [33] when offered traffic load exceeds available capacity at any point in a network causing overall channel quality to degrade and loss rate to rise, leading to buffer drop and increased delay. Congestion has negative impact on network performance i.e. indiscriminate packet loss, increased packet delay, wasted node energy and severe fidelity degradation. Constrained resources, interference coupled paths and the lack of centralized problem make congestion problem in Wireless Sensor Network more challenging Therefore congestion has to be controlled for prolonged system lifetime. Types of Congestion [34]: Generally there are two types of congestion. Node-level congestion is caused by buffer overflow in the node and can result in packet loss and increased queuing delay. Link-level congestion is caused due to collisions when multiple active sensor nodes try to seize the channel at the same time. It increases packet service time and decreases both link utilization and overall throughput and wastes energy at the sensor nodes. Various congestion control schemes [39] Congestion detection Congestion notification Rate adjustment. 9

3. DESIGN/METHODOLOGIES 3.1 Secure Multipath Routing Protocols in Wireless Sensor Networks Till date many routing protocols have been proposed for wireless sensor networks, but only few of them consider the problem of security [4] and most of them are developed without any security concern. So in this section we focus at selected multipath routing protocols in order to cope with the various attacks. 3.1.1 SEER (Secure and Energy-Efficient multipath Routing protocol) SEER similar to Server/Client [14] software architecture where base station does the route discovery and maintenance as well route selection, similar to the server which process everything and client are only responsible for submitting requests to and displaying responses from servers. The route selection is based on the current energy level of nodes along each path. SEER has three phases of Topology construction, Data Transmission and Route maintenance. To initiate the construction the base station first broadcasts a Node discovery message to the whole network and upon receiving the packets the node updates its neighbor list and check the packet sequence number in the table of received packets. If the message has been already received drop this otherwise rebroadcast its neighbors. After that base station again broadcasts Neighbor collection in order to collect the neighbor information of each node. The messages Neighbor collections reply add any unknown node to the neighbor list. Upon receiving neighbor s information the base station then constructs a weighted directed graph, in that case Neighborhood matrix is used to represent relation between nodes. In data transmission phase the base station broadcast an enquiry message and the sensor nodes that satisfy the enquiry response reply with a Data Enquiry Reply packet, and thus calculates the shortest path to the desired node in the weighted graph having minimum sum of energy from the view of the whole network. Modified Breadth first search (BFS) algorithm is used to consider the shortest path as well as the left energy. On selection of the route the base station sends the Route reply packets to the selected source node. On receiving the packet it returns an acknowledgement(ack) to base station to confirm.if the base does not receive the ACK within predefined time it cancels the selected route and again runs the BFS. SEER distributes the communication load among multiroute between source and destination thus avoiding using up energy on one specific route. After a number of transmissions the base station calculates again to select another path to avoid exhausting energy of nodes on one specific path. Security Feature of SEER: In case of SEER algorithm the routing path between the source and sink node is selected by the base station instead of the source or sink node. This feature 10

determines that SEER can defend specifically against attacks on routing protocols that attract traffic by advertising high quality route to the base station. It can defend wormhole, sinkhole and selective forwarding attacks. Advantages: (I) Mitigates the load of sensor nodes by transferring routing related tasks to the base station. (II) Extending the lifetime of the whole network by using multipath to transfer data, (III) Reducing the transmission delay through using the shortest and reliable path. (IV) Resistant to attacks that molest sensor networks by advertising high-quality route to BS. (V)There is a three phase process to check that all nodes are added in the neighbor list, in case they are not added due to collision occurring at each node that results failing to receive ND from some neighbors. (VI) Sequence Number is attached with each packet so if a compromised node selectively drops packets it will be detected by the next hop node. Limitations: (I) The whole SEER protocol depends upon the base station, so it may be hazardous if the base station crashes or acts maliciously the entire network will be affected. (II) SEER is mainly a flat protocol and does not support hierarchy feature. (III) In the topology construction phase large number of transmission thus limiting the network lifetime. (IV) It justifies the security without any cryptographic mechanism. 3.1.2 SCMRP (Secure Cluster Based Multipath Routing Protocol): It proposes a secure cluster based multipath routing protocol. Initially at the time of deployment all node possess unique ID, a certificate (signed by authority i.e. base station), a unique shared key (shared with base station) and a public key of the base station. For neighbor detection the node start broadcasting and receiving packet which contain unique ID and Certificate of the node. On receiving the detection packet the node will first authenticate the node ID by verifying the certificate. After verification sender node ID is added into the neighbor list, otherwise drop the packet. On completion of this phase all information are collectively sent to the BS. After getting information from all nodes the base station produce a neighbor matrix on which applying DFS algorithm BS can find multiple paths from it to every node. Before that BS has to calculate the 11

secret key for every pair of neighbor nodes called pairwise key and unicasts the pairwise keys to the respective nodes. The election of cluster head is based on the residual energy as in EECS [16] and is assumed that all nodes energy level are same before starting the cluster formation. Afterwards BS unicast the intimation packet to the cluster heads with the calculated routing paths from cluster head to the BS. Data transmission mainly consists of three components. First the member node transmits the sensed data to the cluster head with the encrypted and authenticated form. Second cluster head aggregates and compresses the received data to the new signal and sent to the BS with the prescribed route. Third the base station will use unique shared key to decrypt and authenticate the received data.bs continuously monitors the residual energy of the existing CH, if found below the threshold value it elects another CH based on residual energy and conditions, described earlier. After electing CH, network follows the same procedure to intimate the CH and formation of cluster. Similarly if the routing path residual energy goes below the threshold or any node fails, BS selects another path and sends the routing path to the respective CH. Security Issues in SCMRP Key management Analysis of SCRMP: SCRMP uses digitally signed certificate to every node so that no adversary can create a forge ID. Each node has a unique shared key with the BS.A node who wants to send a message to the base station, will encrypt it and create a MAC with the unique shared key, so that only BS can access it. So any adversary can t perform eavesdropping or altering to the message. In this way if any fake node using the ID and certificate of other node, will not be able to use pairwise key. Pairwise key Establishment with a new node: When any new node is introduced in the network, and want to be part of the communication it will broadcast the NEW JOIN packet. Each neighbor who receives the NEW JOIN packet: 1) Check the authenticity of the node and if found legitimate add its ID to the neighbor list.2) Send the information to the base station about the newly joined node and wait for pairwise key.3) After getting the pairwise key and an encrypted packet intended to the new node, neighbor node sent a CHALLENGE and wait for CHALLENGE REPLY. The pairwise key establishes as soon as the neighbor node get back the CHALLENGE REPLY with the expected format. It defends Sybil, Sinkhole, Wormhole and Selective forwarding attack. Advantages: (1) Security towards various network layer protocol attacks. (2) Efficiency and reliability to the network. (3)Resiliency to the path on node failure 12

(4) Alleviate the burden of the sensor node by transferring route and key related task to the base station. Limitations: (1) SCRMP uses shared key management scheme, therefore it may break the system if an attacker find the key. (2) SCRMP although solves orphan node problem but increment of orphan nodes can decrease the performance of the network, so we must restrict the number of orphan node requests. 3.1.3 MSR (A Multipath Secure Reliable Routing Protocols) In MSR three components has been proposed as follows. On demand multiple routing protocols starts by discovering multiple paths between a source and a destination. It provides an easy mechanism to distribute traffic and the network s load. In MSR, it consists of two phases: Route Request and Route reply. In Route request phase source floods a message to find routes towards its destination with unique source ID, destination ID and request ID fields. In order to form disjoint paths, an intermediate node which receives many ROUTE- REQUEST messages with same request IDs processes only the one with minimum hop count. To form multiple paths when the destination node receives the first ROUTE-REQUEST message with certain request IDs starts the timer. All Route requests messages with the same request IDs that arrive before timer expires are considered as alternate routes. In route reply the destination node will send a ROUTE-REPLY message, with a hop count field set to zero, for each ROUTE- REQUEST message it receives before the timer expires. The format of the ROUTE-REPLY message is the same as the ROUTE-REQUEST message. Each node that receives a ROUTE- REPLY message increment the hop count of the message and then forwards it to the neighbor from which it received. Enhanced Passive Acknowledgment refers to the sender passively listening to the channel after finishing the packet transmission to confirm that the packet has been received by the destination. This comes indirectly by overhearing the next node forwards the packet to its next hop neighbor. If a node does not get a message, it timeouts and retransmits the packet. Compared to explicit acknowledgement (ACK), this saves the overhead of sending the ACK packet and hence saves energy. MSR further increases the benefit of Passive acknowledgement by leveraging it to detect security attacks by analyzing the overhead packets as follows: A consistent dropping of a packet from a neighbor can be used as a sign of black hole attack [19].Packet headers can be checked to detect any malicious changes in the headers. This can be used, e.g., to detect IP address spoofing. The packet content itself can be analyzed to detect any unauthorized/suspicious changes to the packet. It also can be used for detecting link failures. 13

Erasure Coding: Erasure coding provides an efficient option for achieving reliability [20] without end-to-end retransmission. It improves reliability in WSNs with minimal overhead. Erasure coding is a coding technique that converts a message into a set of coded shares so that any sufficiently large subset of the coded shares can be used to reconstruct the original message [21]. It can reconstruct original message by receiving any m out of n coded words n>>m. MSR leverages erasure coding to enhance the reliability and security of its operation in WSNs. MSR Security Analysis: MSR handled attacks can group among three different categories. 1) Attacks Prevented by MSR: Hello flood attack, Black hole attack, Selective forwarding attack: Acknowledgment spoofing attack, Replay, Alter and Spoofing attacks.2) Attacks whose Effect is Reduced by MSR: Sinkhole attack, Wormhole attack.3) Attacks that Require Further Processing: MSR currently does not handle the Sybil attack but can be extended to defend against this attack using different techniques including registration, authentication, sharing random keys, and RF position verification [22], [23]. Advantages: 1) MSR provides security against various attacks. 2) Erasure Coding technique enhance the security and reliability in WSNs. 3) Reduces the Traffic overhead. 4) Enhances the Fault Tolerance and bandwidth. Limitations: 1) MSR cannot detect Sybil attack. 2) MSR has end to end delay due to erasure coding and decoding techniques at the source and destination. 3) Routing overhead increases with increase in code rate 3.1.4 meendmrp (A secure Energy Aware Multipath Routing Protocol) The proposed protocol provides Security by digital signature based cryptographic system used with RSA and MD5 hash function. The main idea behind meendmrp is to lower the transmission range of a node to reduce energy consumption. This node disjoint multipath protocol consists of Route construction and Data transmission Phase. 14

In route construction If the node s hop count is greater than the route construction packet s hop count then the packet will be received, processed and forwarded, else the packet will be discarded after updating the routing table without forwarding. Routing table construction, distance exchange and public key exchanges are also done. If the route construction packet is received properly by any node, then its route construction sequence number will be incremented by 1 before forwarding. In data transmission phase multiple paths are found based on the primary path and the data is transmitted based on path cost. Path cost is calculated based on residual energy of the node. Primary Path Selection is based on the maximum path cost.if the data load is minimal then the number of paths will be less. Again if the data load is heavy, the number of paths chosen for the data transmission will be more. This protocol provides energy efficiency through multipath routing and transmission range adjustment of the nodes in the paths. Security in meendmrp: meendmrp uses RSA and MD5 hash function. Before transmission the document will be digitally signed and receiver checks the digital signature to ensure the authorization of the document. In the sender side, encrypted message digest will be produced and this signature is sent along with the document. For the encryption RSA private key is made use of. To produce message digest MD5 hash function is used. The original message along with the digital signature is transmitted. Figure 1 depicts the sender side digital signature generation. Figure 1: Sender side digital signature Generation Digital signature verification is done at the receiver end. If the decrypted digital signature and the message digest produced by the MD5 hash function are equal, it is a valid message else the message is discarded. It is depicted in the Figure 2. 15

Figure 2: Receiver side digital signature verification Advantages: 1) Provides transmission range adjustment of the nodes. 2) Provides security using Asymmetric key cryptography using RSA and MD5 and hash function due to which size of message won t be increased. 3) Provides reliability through load balancing and effective multipath selection based on the primary path. 4) Byzantine attack, Selective forwarding and Altered Routing can be defended using meendmrp. 5) The signature side verification time of RSA is very less compared to other algorithm. Limitations: 1) Use of Asymmetric key cryptography increases the computational complexity. 2) Periodic updation of the keys in the network is recommended to protect the network from eavesdroppers. 3) Only supports text data routing. 4) Attacks like Wormhole, Sybil, Routing table poisoning, Resource depletion attack cannot be defended. 5) Increase in the transmission range irrespective of number of nodes and size of network may lead to high energy loss. 16

3.2 Energy efficient protocols The main design goal of WSNs [25],[26] is not only to transmit data from a source to a destination, but also to increase the lifetime of the network which can be achieved by employing energy efficient routing protocols. Thus in this work, a study on various protocols coming under power management and data-driven approaches has been done. 3.2.1 An Energy-Efficient Multipath Routing Protocol for Wireless Sensor Networks A load balancing algorithm is proposed to distribute the traffic over the multiple paths discovered. The multipath routing protocol is used to find multiple disjoint paths between a pair of sink and source nodes. During the initialization phase the HELLO message is exchanged and if received for the first time will be updated in its neighboring table with forward node ID and energy level. In case the node type is set to SINK then the sender ID is compared to sink list of node and a new entry is created in the sink table and the message is broadcasted. At the end of initialization phase each node has their neighboring node table and sink table updated. Path Search Phase is initiated when a set of nodes detect a stimulus and the selected source node begins to send the aggregated data to the sink node. The source node unicasts one REQUEST message to every neighboring node with distinct Route ID. Upon reception of the request the routing table is updated.the selection is based on two criteria: First the neighboring node should not have been selected for another path that connects the same pair of sink and source nodes. Second, the link cost to the selected neighbor has to be the lowest among all the available neighbors which is denoted by Where N a represents the neighboring set of node a. d ay is the distance (in hop count) between node a and sink node, d by is the distance (in hop count) between node b and sink node, and d is the difference between d ay and d by. e b,residual and e b,init represent the residual and initial battery level of node b, respectively. Finally, the node will update the field path cost, forward node ID and forward node energy level before sending the REQUEST to the neighbor selected. If none of the neighbors satisfies the conditions, the REQUEST will simply be dropped. In case of sink node it first examines the source ID and updates the source table and routing table if needed. Sink node distributes the traffic via ASSIGN message in the multipath along with the transmission rate assigned to each path. 17

After multiple paths are discovered, the source node begins to transmit data packets with the assigned rates on each path. At the sink, it updates the path cost in its routing table each time a DATA message arrives. The sink node will then adjust the traffic flows and notify the source node with the ASSIGN messages. The sink node detects a path as failure in case delay of data packets in path is over a threshold value. If the number of current working path lowers to two or below sink will send a RESET message or may otherwise adjust the data allocation rate to avoid invoking path search frequently. Load Balancing Algorithm: It assumes that there exists N disjoints paths between a source node x and a sink node y.the requested data rate to be arrived at the sink node y via all these multipath is R bits/sec. Let r j be the data rate allocated to path j. For a path j, the product of the path cost p j and the data r ate allocated r j gives the path cost rate c j. Load balance ratio different multipath: (also known as fairness index) to evaluate the level of load balancing over Where the vector r denotes the traffic rates allocated to all available routes and r j is the traffic flow allocated to path j.the load balance ratio in equation reaches its global maximum of 1 under the condition that the traffic is perfectly balanced. The node energy consumption measures the average energy dissipated by the node in order to transmit a data packet from the source to the sink. where M is the number of nodes, e i,init and e i,res are respectively the initial and residual energy levels of node i, S is the number of sink nodes and data Nj is the number of data packets received by sink j.the control message overhead counts the average amount of control messages received and transmitted by each node in bytes. It evaluates the extra workload required to sustain the data routing for various schemes. The average delay measures the average time spent to relay data packets from the source node to the sink node. Advantages: 1) It is observed that there is a lower node energy consumption of this multipath protocol over other schemes. 2) Increase of the network size has little impact and the energy efficiency remains stable. 18

3) The control message overhead is much less and has shortest delay compared to other schemes. 4) The multipath routing has the shortest delay compared to other schemes and congestion can be avoided. Limitations: 1) Node disjoint paths are a very strong condition when aiming to find multiple paths between two nodes and may result in rather inefficient and suboptimal paths in terms of hop count. 2) The RESET message sent by sink node to re initiate the path search phase for finding optimal path can cause overhead. 3) The data aggregation cannot be done by source node when event occurs in different regions within coverage area. 3.2.2 REER (Robust and Energy Efficient Multipath Routing Protocol) REER uses the residual energy, node available buffer size, and Signal-to-Noise Ratio (SNR) to predict the best next hop through the paths construction phase. Path Discovery Phase is based on the idea of Directed Diffusion [32] the sink node starts the multiple paths discovery phase to create a set of neighbors that able to forward data towards the sink from the source node. In initialization phase each sensor node broadcasts a HELLO Message through the network to get information about neighbors who can provide highest quality data. After initialization phase each sensor node computes cost function of its neighboring nodes. The cost function includes energy factor, available buffer factor and interference factor with appropriate weights. The total cost (C total ) for a path P consists of a set of K nodes is the sum of the individual link costs l (xy)i, i K along the path. For primary path discovery the sink node computes its preferred next hop node using link cost function and send out a RREQ message to its next hop, and the operation continues until its source node is reached. For alternate path discovery the sink node sends RREQ message to its next most preferred neighbor. To ensure path disjointedness each node receives only one RREQ message. For path maintenance the source node periodically flood a KEEPALIVE message over alternate paths to keep them alive. After multiple paths have been discovered, the source node 19

begins to transmit data messages to the sink. For the first version (REER 1), uses the idea of cost threshold and transmit the message over the best available path. The second version (REER 2) uses a subset of the available paths to transfer the message in order to distribute the load over the nodes. It splits up the message into small parts, adds error correction codes, and then transmits it over multiple paths simultaneously to increase resiliency to path failures and ensure that an essential portion of the packet is received at the destination without incurring excessive delay through data retransmissions. Average Energy Consumption: The average energy consumption is the average of the energy consumed by the nodes participating in message transfer from source node to the sink node. As the network size increases, REER 1 becomes more stable than other protocols. REER 2 consumes more energy than REER 1, because of the overhead induced by computing and sending of correction codes. The energy consumption of REER 1 is more stable and has a little impact by the increase in the network size when compared to REER 2. Advantage: 1) It is a robust and energy efficient multipath routing protocol. 2) Using this technique, failure in one or more paths can be recovered without invoking data retransmissions and thus reduces overhead. 3) In REER2 splitting the message and adding FEC codes increases the resiliency and reduces excessive delay in data transmission. Limitations: 1) Switching of from the primary path to the alternative path incurs an overhead. 2) In REER 1 phase if all the routes in the routing table fail, the source initiates route discovery message which may cause some overhead. 3) REER 2 consumes more energy induced by computing and sending of correction codes. 4) With increase in network size performance degrades due to more power consumption to send data. 3.2.3 EEIAMR (Energy Efficient Interference Aware Multipath Routing) EEIAMR chooses a partial disjoint path in case of node failure to minimize routing overhead and increase reliability of packets reaching the destination with minimum delay. 20

For each node find neighboring nodes The sink broadcasts messages to create Neighbor Node table at each node to maintain the addresses of all the nodes that are able to communicate with the node directly without using relay node during topology setup. Find paths from source node when the source node detects an event to forward data it starts Route Request procedure and sends the requests only to the neighbor nodes in NN table. Every node forwards the requests until the sink is reached. Since it restricts flooding, overhead is lowered and path is chosen based on minimum hop count. Data transmission Data is transmitted once path are discovered for data transmission. To forward the data each selected sensor node do not need to maintain whole path information. A node with large residual energy and farthest from the previous one is selected as the next intermediate hop. In alternate path while transmission if a node fails to transmit data due to less energy, node or link failure then partially disjoint path based on the NN table information is selected to route the traffic to find another neighbor node as the next hop node. From the new selected neighbor node again forwarding principle is executed and it may rejoin the primary path which in turn reduces the path length. Energy model: The energy consumed to transmit a k bit message at a distance d is E Tx (k,d)=eelec K+Eamp k d 2 E Rx (k) =E elec k Where E elec is the dissipated energy by the radio to run the transmitter or the receiver circuitry and E amp is the required energy by the transmit amplifier. We observe that EEIAMR introduces less routing overhead using short alternate paths with less number of nodes and hence less energy consumption. Advantages: 1) With the increase in network size the path length becomes even small and reduces the energy consumption. 2) There is no flooding of messages so less overhead. 3) The ability to choose alternate paths when there is lower energy node in the primary path, distributes the energy consumption and maximizes network lifetime. Limitation: 1) Transmission of multimedia based data has posed additional challenges i.e. severe energy constraint of sensor nodes. 21

2) Partial node disjoint path may have some nodes in common and failure in one such node can disable more than one paths. 3.2.4 BEER (Balanced Energy Efficient Routing protocol) This protocol chooses one route among several routes with a probability which will count the residual energy, the energy of communication and the number of paths including the forwarding nodes. The protocol aims to improve the lifetime of wsn by ensuring balanced energy consumption among all the sensor nodes of the network. The protocol consists of three phases. In Setup Phase a route request message containing a cost variable initialized to 0 is broadcasted by the sink. Each node receiving this message broadcast it to his neighbors. But before, it calculates the cost of the communication with the neighbor who has sent back the message and add it to the whole cost of the path to the sink. Neighbor nodes with paths having minimal cost are added to the forwarding table, then, an Forwarding Table Message that contains the identifiers of these nodes is broadcasted by the node.each node receiving FTM messages, count the number of FTM messages containing its identifier. So, each node i establishes a set of the neighbors j sending an FTM message containing the identifier i as following: NF= {j i F T M (j)} Once all FTM messages are received by node i, it calculates the variable N that represents the cardinality of the set NF: N= NF Hence, the node i insert the variable N in an NFTM message (Number Forwarding Table Message) that it sends to its neighbors as response to FTM messages. Receiving the NFTM, Now, a node can calculate probabilities P ji assigned to each node of the forwarding table. This probability depends on the path cost (Cost ji ), the number of nodes that use this path (N i ) and the With 22

Where, FT j is the forwarding table of node j and nbchemin is the number of routes in the forwarding table of node j. The last step in this phase is the broadcast of the route request message by node j until it reaches source nodes. Nevertheless, the route request message is updated by each node before broadcast it. The value of the Cost field of the message is replaced by the average cost of reaching the destination through the neighbors nodes of the forwarding table which is calculated with the formula: In Data Communication phase, source nodes and intermediates ones choose randomly a neighbor to route data using probabilities calculated earlier. In Route maintenance localized flooding is performed frequently from destination to source to keep all the paths alive. Advantage: 1) The protocol consumes energy in a fair manner to enhance network lifetime. Limitation: 1) The calculation of probability before forwarding data creates overhead. 23

3.3 Congestion Control Protocols: Congestion control in WSN [31],[32] is particularly difficult as a WSN can usually remain idle for a long period of time and then suddenly become active in response to a detected event, generating a large amount of information from the sources (sensors) to a sink. Even if an event is a few bytes long, the high number of events due to high reporting rates will rapidly create shortage of resources (buffer space, battery life) in the WSN leading to congestion and consequently packet/event drops. The following protocols are designed to control congestion. 3.3.1 SLiM (Simple Lifetime based Multipath routing protocol) The load repartition strategies distributes the traffic uniformly on available paths simultaneously.the source tries to balance its traffic on available paths in order to keep its sending rate unchanged while reducing the amount of data sent on the current active paths. The network model provides knowledge from source and all intermediary nodes of all available paths to the sink. It adopts the sink initiated approach where sink is the originator of the request and floods the network with a request until the sensor, referred to as source is reached.with one flooding, multiple paths are built and maintained at intermediate nodes towards the sink. Load repartition strategies Three load repartition strategies for congestion control, from mode 1 to mode 3 is defined. For the purpose of comparison, mode 0 refers to the no load repartition scenario in which a source uses the same path without any congestion control concerns. In mode 1 the source uses all the available paths to a sink from the beginning of the transmission. The traffic is then uniformly load balanced on these paths. Mode 0 and mode 1 therefore represent the 2 end-points in the load repartition strategies design space. In modes 2 and 3, explicit congestion notifications are used. At every intermediary node, when the reception queue occupancy is greater than a given threshold or when the collision rate is above a given threshold, a Congestion Notification (CN) message is sent back to the sources for each path id known by the node. A CN message contains the node id and the path id:cn(nid,pid). The basic principle behind these load repartition strategies is to make each source aware of a congestion on path i and reacting to it by loadbalancing the current traffic on this path on a larger number of paths. Congestion Analysis In mode 0, the different sources transmit data with a fixed rate using only one path without any congestion control. Intermediate nodes, when overloaded, drop packets and hence the number of 24

dropped packets is the largest compared to the other modes. Mode 1 gives the best performances is due to the fact that the sources distribute their flows on all available paths from the beginning hence reducing the probability of overloaded queues. However, it is observed that mode 3 tries to balance the load of a congested path on the other paths does not succeed in reducing the drop rate when compared to a simpler approach such as mode 2, at least for small network size. Advantage: 1) Load repartition does improve congestion control by reducing the packet drop probability. Limitation: 1) Flooding technique is used for multipath configuration thus causing some overhead. 3.3.2 GMCAR (Grid based Multipath with Congestion Avoidance Routing) GMCAR protocol is a new grid-based multipath routing protocol intended to route packets fast, utilize and extend sensor nodes energy in addition to avoiding and handling network congestion when happens. In Grid formation phase square shaped grids of predefined size are formed. Any node in one grid can reach any other node in any neighbor grid. Initially for each grid a master node is selected randomly and remaining are non-master nodes. The master node is selected based on the node remaining energy. Figure 3: Multi-path routing in grid based network. After forming the grids, the sink initiates a flooding message to discover paths from each grid to sink. Upon receiving the flooding message each master node broadcasts routing information such as hop count and grid density to its neighbor. Each available path is assigned a weight function based on number of hops and the density of the first grid along this path. After establishing the routing tables, nodes can start transmitting their data. Each non master node transmits any information to the grid master node, which in turn is responsible for selecting the suitable path to forward the data. 25

Congestion Avoidance : We avoid congestion occurrence by creating multiple diagonal paths to the sink where the master nodes can distribute the traffic along these paths. Load balancing is used when two of the alternative paths have the same weight keeping the load evenly distributed. Congestion Control Short Term Congestion Control: Short term congestion control happens in intermediate nodes due to sudden increase in the traffic going through these nodes; this kind of congestion could be eliminated by diverting the traffic to other nodes. Upon detecting congestion, the node broadcasts a route invalidate message to the neighbors and sets up a timer.any master node in neighbor grids receiving this message invalidates the routes to the grid whose master node initiated the invalidate message and start using the alternative paths only. When the timer timeout elapses, the node initiates route validate message to enable the route that was previously invalidated. If the node s buffer still overloaded the node decides to start long term congestion control mechanism. Long Term Congestion Control: In this protocol, the path that has small hop count and high density is assigned a high weight and thus will be chosen continually for packet forwarding. If this happens, the master nodes along such path may not be able to route all the incoming traffic leading to a situation that is known as long term congestion. The proposed solution for handling long term congestion implies using a secondary master node. The secondary master node is selected based on its residual energy. The routing information stored in the master node is then passed to the secondary master node. In a way that guarantees fairness (such as load balancing), the master node can choose between handling the traffic or dispatching the traffic to the secondary master node. Advantages: 1) Superior in saving node energy and extend network lifetime. 2) During topology change few control messages are exchanged between the master nodes without flooding the network. 3) GMCAR makes greater use of the available queues because High queue occupancy is really desirable for sensor networks as it indicates higher resource utilization and fairness. 4) Handles both real time and non-real time applications in wireless sensor networks. Limitation:1) If the master node is the only remaining node in the grid, the master node broadcasts a routing update message to the neighbor grids to invalidate any path going through this grid. 2) Flooding of messages from sink to discover path may cause overhead. 26

3.3.3 Multipath Routing With Novel Packet Scheduling Approach in Wireless Sensor Networks The proposed multipath routing algorithm enables the reliable delivery of data. This algorithm provides an efficient way to prevent packet loss at each node which results in congestion management in the sensor network. Figure 4: Network Model Network model is aimed, to help a node requesting a certain service to the network, to find the most appropriate route providing the right requested service. Source dynamically assigns the priority of the individual application data. Figure 4 depicts a multipath route from source S to sink. A prioritizer is provided at the network layer and it classifies the traffic according to the priority of the data and places the data in the appropriate queue by reading the packet header which includes a priority number for each type of packet and it is assigned at the source end. The data packets are scheduled for transmission based on the priority assigned, by a scheduling unit. It decides the order of service for the data packets. The scheduling unit consists of a software layer which applies the Earliest deadline first (EDF) algorithm, which assigns priorities to individual jobs in the tasks according to their absolute deadlines. By controlling the scheduling rate, it is possible to prevent congestion and packet loss in the network. EDF algorithm will search for the process closest to its deadline. This process is the next to be scheduled for execution. 27

Figure 5: The Queuing Model for a Node The Figure 5 depicts the queuing model for a node. There will be inter queue priority and intra queue priority. The queue for transit data has higher priority than the queue for the originating data. Each node checks the priority number and the source address at the header of the packet on the arrival of the packet, orders the packet and puts the packet in the appropriate queue. Once the queue is selected, the packet which has higher priority is selected from the header of the packet by reading the priority number and the EDF algorithm will schedule the transmission. A multipath routing protocol involves the path discovery, traffic distribution and maintenance of the paths. The scheduling rate gives the number of packets the scheduling unit schedules per unit time from the queues. For each node with multiple parents, the net scheduling rate of a node is the sum of scheduling rate required for each of the parent node. By controlling the scheduling rate, the flow control and congestion control are done. By adjusting the scheduling rate the buffer overflow is avoided. Advantages: 1) Load Balancing is achieved by data traversing the available multiple paths from source to destination. 2) A shorter path is chosen which involves less number of sensors and consequently less utilization of resources such as energy and bandwidth. 3) Increase in packet service ratio, packet drop decreases. 28

Limitation: 1) Increase in the rate of scheduling may cause buffer overflow at the node. 3.3.4 Priority Based Congestion Control For Heterogeneous Traffic In Multipath Wireless Sensor Network This protocol is based on priority to control congestion for heterogeneous traffic in multipath wireless sensor network. It allocates bandwidth proportional to the priority of many applications simultaneously running in the sensor nodes. System Architecture Figure 6 represent the system architecture where The Congestion Detection Unit (CDU) calculates the packet service ratio. When the value of packet service ratio is less than 1, it indicates congestion. With the help of Rate Adjustment Unit (RAU), each parent node allocates the bandwidth to the child nodes according to the source traffic priority and transit traffic priority. The Congestion Notification Unit (CNU) uses an implicit congestion notification by piggybacking the rate information in its packet header. All the child nodes of a parent node overhear the congestion notification information. Figure 6: System Architecture 29

Queuing model Figure 7 show the queuing model of each sensor node. To differentiate different types of traffic in the heterogeneous network a source sensor node adds a traffic class identifier to identify the traffic class. For each traffic class a separate queue is maintained in the sensor nodes. The classifier classifies the packets based on the traffic class and sends them to the appropriate queue. Figure 7: Queuing Model The following are the descriptions of the queuing model. Originating Rate R i org: It is the rate at which a sensor node originates data. Scheduling rate R i sch : It is defined as the rate at which the scheduler schedules the packets from the queues. The scheduler of node i, forwards the packet from node i-1 to the next node i+1. Average packet service rate R i serv: It is the average rate at which packets are forwarded from the MAC layer. The scheduler schedules the packets from queues according to the queue priority. The packets from higher priority queue will be serviced more than the packets from the lower priority queue. Transit traffic is given more priority than source traffic. Congestion detection The packet service ratio r(i) is used to measure the congestion level at each node i. Packet service ratio is calculated as Where R i serv : packet service rate of node i R i sch : packet scheduling rate of node i. 30

Here, the packet service rate R i serv is the inverse of packet service time. The packet service time is the time interval when a packet arrives at the MAC layer and successfully transmitted towards the next hop. The packet service ratio r (i) reflects the congestion level at each sensor node. When r (i) =1, R i schz=r i serv In both these cases, there is no congestion. r (i)>1, R i sch < R i serv. r (i)<1, R i sch> R i serv causes queuing up of packets and indicates congestion. Implicit congestion notification Each node piggybacks the scheduling rate of its children in the congestion notification information. All the child nodes of node i overhear the congestion notification information and they control their rate according to it. Rate adjustment is done hop by hop. It ensures that the heterogeneous data from different stations will reach the base station at the desired rates. When each node receives the congestion notification information, it adjusts its rate accordingly. If the packet service ratio is less than the threshold value β, it notifies congestion, then node i will adjust the scheduling rate. If the packet service ratio is greater than 1, indicates that the packet service rate is greater than the scheduling rate. So each node will increase the scheduling rate for parent j to improve link utilization otherwise the packet service rate is equal to the scheduling rate. To increase the scheduling rate, the value of α is chosen smaller than but close to 1. Advantages: 1) This technique is able to control congestion of heterogeneous data from different applications. 2) Instead of distributing the traffic among multiple paths, the parent node divides the bandwidth among child nodes according to the global priorities of child nodes. Limitation: 1) Packet drop ratio, delay is not considered under this protocol. 31

4. RESULTS AND INTERPRETATION Table 1: Taxonomy of Secure Multipath Protocols Protocol Path Chooser Path selection Criteria Topology Security technique Attacks Defended Energy/ Congestion Efficient SEER Base station (BS) Alternative multipath Based on BFS and residual energy Flat BS defends attack. Wormhole,Sinkhole,Selective forwarding Energy efficient SCMRP Base station Alternative multipath based on residual energy and power Hierarchical 1)Digital certificate 2)Unique shared key 3)public key Sybil, Wormhole, Sinkhole, Selective forwarding, Hello flood, Spoofing Energy efficient MSR Source Concurrent multipath Flat 1)on demand multipath routing2)enhanced passive acknowledgement3)erasure coding Hello flood, Black hole, Selective forwarding, Replay, alter, spoofing, Wormhole, sinkhole. Congestion reduced meendmrp Sink Concurrent multipath Flat RSA,MD5 hash function Byzantine, Selective forwarding, Altered routing Energy efficient as well Congestion reduced 32

Table 2 Taxonomy of Energy efficient multipath protocols Protocol Path Chooser Path Selection Energy technique Secure/Congestion Energy efficient routing protocol Node detecting stimulus Node disjoint alternative path routing Fairness index based on hop distance of nodes and energy levels. Congestion aware REER Sink Both alternative and concurrent multipath routing Based on Residual energy, node available buffer size, SNR, FEC. Congestion is balanced EEIAMR Sink Partial disjoint path Short alternate path with less number of nodes. Congestion overhead reduced. BEER Sink Path selected based on probability Routes chosen according to probability based on residual energy, energy of communication, Number of paths. Not applicable. 33

Table 3 Taxonomy of Congestion aware multipath protocol. Protocol Path chooser Path selection Congestion technique Secure/Energy aware SLiM Partially disjoint path Sink Load repartition strategy Not applicable GMCAR Diagonal multipath Master node Grid based multipath Energy efficient Novel packet scheduling Partial node disjoint path Source Controlled scheduling rate of packets Energy aware Priority based congestion control Queuing model for multipath Source Priority based weighted fairness Energy aware 34

5. CONCLUSION AND FUTURE SCOPE In this present work a comparative analysis of the most recently proposed multipath routing protocols for wireless sensor network (WSN).The three most important challenges of sensor network that is Security, Energy efficiency and Congestion control. We have also highlighted the advantages and limitations of each routing protocols. It discussed about security and its requirement in various domains of wireless sensor network. In this context four secure based multipath routing protocols which can handle the various attacks and intrusions in sensor network are discussed.there are many security solutions that have been proposed but no standard security mechanism can provide overall security for wireless sensor network. Designing a secure WSN needs proper mapping of security solutions with different security aspects.in time to come, we must be ready to accept many more unique design of WSN, more sophisticated attacks and their preventions. Energy resource limitations are of priority concern in sensor network. Distributing the loads to nodes significantly impacts the system lifetime. One of the goals of this protocol is to select the best path so that total energy consumed by the network is minimized. The four protocols discussed improves the energy constrained network.there the sensor nodes are mostly stationary thus research can be done by assuming sink and source as mobile and results can be improved by multiple sink nodes. Congestion is an essential problem in WSN that leads to packet loss, transmission latency and has impact on energy efficiency and therefore must be efficiently controlled. Thus in this context four recent protocols that tried to cope with this problem with certain limitations. So through this survey it is concluded that congestion control is a matter of great concern and should be dealt effectively such as QOS, Energy efficiency is necessary. 35

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