International Journal of Research in Engineering Technology and Management ISSN 2347 - 7539 Comparative Study of TCP Variants in Wireless Sensor Networks Nutan K Bhati1, Dr. Ashish Bansal2 1 Research Scholar, Information Technology, SVITS, Indore, MP, India, [email protected] 2 Professor, Information Technology, SVITS, Indore, MP, India, [email protected] Abstract This paper presents survey analysis which aims at comparing the TCP variants in wireless sensor networks [WSN]. Wireless sensor network is a high and new technology consists of spatially distributed autonomous sensors to monitor physical or environmental conditions. In monitoring of physical environments, the most important application of wireless sensor network is monitoring of critical conditions. The most important in monitoring application like critical condition is the sensing of information during emergency state from the physical environment where the network of sensors is deployed. A big challenge to sensor networks is a fast, energy consumption, reliable and fault tolerant channel during emergency conditions to sink (base station) that receives the events. Our focus is to discuss the various routing protocols like Ad hoc On Demand Distance Vector (AODV) and Dynamic Source Routing (DSR), Dynamic MANET On-demand (DYMO) for monitoring of critical conditions with the help of important metrics like network load and media access delay. Keywords: Wireless sensor networks (WSN), Ad hoc On Demand Distance Vector (AODV), Dynamic Source Routing (DSR), Routing Protocol. --------------------------------------------------------------------***---------------------------------------------------------------------- 1. INTRODUCTION Wireless Sensor Network (WSN) includes many sensor nodes. Those nodes can quickly detect the environmental parameters. It can be used to bridge the gap between physical and virtual world. WSNs have a variety of applications such as medical, home security, machine diagnosis, military Information, environmental monitoring, agriculture, etc. WSN is emerged from the fusion of Ad Hoc Network and the supervisory control and data acquisition (SCADA) systems [1][2]. WSN derives the networking characteristics of ad-hoc network and combines it with the hardware facilities of tiny sensors. Once a sufficient number of nodes have been deployed, the sensor network can be used to fulfill its task. A wireless sensor network (WSN) of spatially dispersed selfgoverning sensors to monitor physical or environmental conditions like temperature, pressure sound etc. and to cooperatively pass their data through the network to a main location. Wireless sensor network are of two types i.e., unstructured and structured. The structured wireless sensor networks are those in which the sensor nodes positioning in a planned manner while in unstructured wireless sensor networks are the one in which sensor nodes positioning in an ad-hoc manner. As there’s no stable infrastructure between wireless sensor networks for communication, routing becomes a concern in large number of sensor nodes deployed alongside challenges of producing, design and management of those networks. There are different types of protocols that have been planned for these problems. 2. ROUTING PROTOCOLS A routing protocol is a protocol that stipulates how routers communicate with each other, distributing information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms. Every router has prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbor’s, and then throughout the network. This way, routers gain knowledge of the topology of the network. Routing protocols are used in the implementation of routing algorithms to facilitate the exchange of routing information between networks, allowing routers to build routing tables dynamically. Routing protocol updates are exchanged by routers to learn about paths to other logical networks. Each routing protocol offers features that can make it desirable as part of an internetwork design. There are various routing protocols that have been proposed for routing data in wireless sensor networks due to such problems. The routing protocols that are location based relay data to the desired destination instead of the whole network by utilizing positioning information. In some applications there is requirement of QoS along with the routing functions that are based on network flow modeling. There are mainly three types of routing protocol is present in the network: 1. 2. 3. Reactive Routing Protocol Proactive Routing Protocol Hybrid Routing Protocol 1. Reactive Routing Protocol – These protocols only find a route to the destination node when there is a need to send data. _______________________________________________________________________________________ Volume: 02 Issue: 03 | May-2014, Available @ http://www.ijretm.com | Paper id - IJRETM-2014-02-03-409 1 International Journal of Research in Engineering Technology and Management The source node will start by transmitting route request throughput the network. The sender will than wait for the destination node or an intermediate node to respond with a list of intermediate nodes between the source and destination. Reactive protocols start to set up routes on-demand. The routing protocol will try to establish such a route, whenever any node wants to initiate communication with another node to which it has no route. This kind of protocols is usually based on flooding the network with Route Request (RREQ) and Route reply (RERP) messages. Reactive routing protocols are:  Ad hoc On Demand Distance Vector (AODV)  Dynamic Source routing protocol (DSR)  Temporally ordered routing algorithm (TORA)  Associability based routing (ABR)  Signal Stability-Based Adaptive Routing (SSA)  Location-Aided Routing Protocol (LAR) 2. Proactive Routing Protocol - Proactive WSNs protocols are also called as table-driven protocols and will actively determine the layout of the network. Through a regular exchange of network topology packets between the nodes of the network, at every single node an absolute picture of the network is maintained. There is hence minimal delay in determining the route to be taken. This is especially important for time-critical traffic. When the routing information becomes worthless quickly, there are many short-lived routes that are being determined and not used before they turn invalid. Proactive WSN Protocols include:  Optimized Link State Routing (OLSR)  Fish-eye State Routing (FSR)  Destination-Sequenced Distance Vector (DSDV)  Cluster-head Gateway Switch Routing Protocol (CGSR) 3. Hybrid Routing Protocol - Since proactive and reactive protocols each work best in oppositely different scenarios, hybrid method uses both. It is used to find a balance between both protocols. Proactive operations are restricted to small domain, whereas, reactive protocols are used for locating nodes outside those domains. Hybrid protocols are:  Zone Routing Protocol, (ZRP)  Wireless Ad hoc Routing Protocol, (WARP)  Hierarchical State Routing (HSR)  Zone Routing Protocol (ZRP)  Landmark Ad Hoc Routing Protocol (LANMAR) ISSN 2347 - 7539 The routing protocols AODV, DSR and DSDV are three of the promising routing protocols. They can be used in mobile ad hoc networks to rout packets between mobile nodes. A) Ad hoc On Demand Distance Vector (AODV) Ad hoc On-Demand Distance Vector Routing protocol (AODV) is an on demand routing protocol. AODV is capable of both unicast and multicast routing. AODV is a reactive type protocol. In reactive routing protocols the routes are created only when source wants to send data to destination whereas proactive routing protocols are table driven. Being a reactive routing protocol AODV uses traditional routing tables, one entry per destination and sequence numbers are used to determine whether routing information is up-to-date and to prevent routing loops. The discovery of the route from source to destination is based on query and reply cycles and intermediate nodes store the route information in the form of route table entries along the route. Each intermediate node in the network forwards the Route Request (RREQ) message until it reaches the destination node. The destination node responds to the RREQ message by transmitting the Route Reply (RREP) message. Control messages used for the discovery and breakage of route are as follows:     Route Request (RREQ) message: It is used to form a route from one node to another node in a network. Route Reply (RREP) message: It is used to connect destination node to source node in a network. Route Error (RERR) message: It is used to indicate any route broken or node failure. HELLO message: It is used to determine the activeness of the network. The transmission of data depends on route discovery and route maintenance in AODV. The route discovery depends on RREQ and RREP messages, if a node initiate’s request of route it will form route after getting the RREP. The route will be maintained by sending HELLO messages to neighbor nodes, if any link failure it will indicate using RERR message. B) Dynamic Source Routing (DSR) DSR is one of the well-known routing algorithms for ad hoc network [5], originally developed by Johnson Maltz, and Broch. Dynamic Source Routing (DSR) protocol is specifically designed for multi-hop ad hoc networks. DSR uses source routing technique in which source node determines the complete routing path through which the data packets are to be forwarded. The source has to explicitly include the set of nodes forming the routes in the packet’s header. This helps in identifying the address of the next hop to which data is to be forwarded. _______________________________________________________________________________________ Volume: 02 Issue: 03 | May-2014, Available @ http://www.ijretm.com | Paper id - IJRETM-2014-02-03-409 2 International Journal of Research in Engineering Technology and Management The difference in DSR and other routing protocols is that it uses source routing supplied by packet’s originator to determine packet’s path through the network instead of independent hop-by-hop routing decisions made by each node. The packet in source routing which is going to be routed through the network carries the complete ordered list of nodes in its header through which the packet will pass. Fresh routing Information is not needed to be maintained in intermediate nodes in design of source routing, since all the routing decisions are contained in the packet by themselves. DSR protocol is divided into two mechanisms which show the basic operation of DSR. The two mechanisms are:   Route Discovery- Route discovery is a mechanism through which a source node obtains a route to a destination node. This is performed only when the source node has data packets to send, but a route to the destination node does not exist yet in its route cache. The source node broadcasts a RREQ packet to all the nodes in the network. A node receiving the RREQ packet sends a RREP packet back to the source node if it is the destination of the RREQ packet or a route to destination exists in its route cache. Route Maintenance- Route maintenance is a mechanism through which a source node detects route faults along an established route to a destination node. This is performed only when a source is using the route for transmission of packets. The source node keeps the route in its route cache for some timeout period after use, and finally deletes it from the route cache when the time out period expires. The route maintenance mechanism verifies validity of the routes in use by the DSR protocol. C) Destination-Sequenced Distance Vector (DSDV) This is one of the table driven routing protocols based on Bellman Ford algorithm mechanism. The main objective is to maintain consistent and up to date route information from each source node to other destination nodes in the network. Each node maintains one or more tables to store the required routing information. These tables are updated according to change in network topology by propagating update information throughput the network. Two key elements are important in such protocol the number of routing tables and the update method being used. The entries in the table are indicated by number assigned by the destination node. These number acts as status indicators of the nodes which therefore minimize routing loops. 1. 2. ISSN 2347 - 7539 Which is infrequently transmitted is called the full dump carries all available routing information. Incremental packet is used to forward only that information which has changed since the last full dump. In DSR, the whole route is carried with the message as an overhead, whereas in AODV, the routing table is maintained thus it is not required to send the whole route with the message during the Route Discovery process 3. SIMULATION AND ANALYSIS METHOD The simulations were performed using Network Simulator (Ns-2), which is popularly used for ad hoc networking community. Ns2 is a discrete event simulator targeted at networking research. It provides substantial support for simulation of TCP, routing and multicast protocols over wired and wireless networks. It consists of two simulation tools. The network simulator (ns) contains all commonly used IP protocols. The network animator (nam) is use to visualize the simulations The routing protocols were compared based on the following 3 performance metrics: 1. Packet Delivery Fraction (PDF): The ratio of Data packets delivered to those generated by the sources. Total Number of Packet Receive PDF = ------------------------------------------------Total Number of Packet Sent The greater value of the packet delivery ratio means better performance of the protocol. 2. End to End delay: the delay in delivering a packet to the destination which is inclusive of all kinds of delay. dend-end= N[ dtrans+dprop+dproc] where dend-end dtrans dprop dproc = end to end delay = transmission delay = propagation delay = processing delay The lower value of end to end delay means better performance of the protocol. 3 .Throughput - Throughput is the average number of successfully delivered data packets on a communication network or network node. Throughput is calculated in bites/sec, data packet/second and data packet/time slot. Updated packets can results in large amount of traffic. Two types of updates packets are present in DSDV based network. _______________________________________________________________________________________ Volume: 02 Issue: 03 | May-2014, Available @ http://www.ijretm.com | Paper id - IJRETM-2014-02-03-409 3 International Journal of Research in Engineering Technology and Management ISSN 2347 - 7539 Total number of received packets at destination Throughput = ------------------------------------------------------Total simulation time Simulation Method - Before we start the simulation, we create 3 template TCL scripts to be used by our batch file to automatically simulate scenarios using the Mobility scene generated by using the setdest toolset. Four Batch files are used : Batch file to run the simulations based on the test scenarios varying speed and pause time, batch file to copy the test scenarios in the template tell script, the batch file to run the awk script and the final batch file to move the nam, trace and mobility scenarios in specific folder for archiving and future use. The simulations parameters are shown in the table below: B. Packet Delivery Ratio Table 1. Simulations parameters C. Average Throughput 4. SIMULATION RESULTS Simulations were done varying the speed keeping the pause time constant (0 sec) and then varying the pause time keeping the speed constant (5 m/s). The variation were done respectively varying the routing protocol from DSR to AODV and then to DSDV. The number of nodes for each comparison were also varied from 15 to 30 to 45 to identify the effect. In all scenarios the Comparison were based on performance metric: Packet Delivery Fraction, End to End Delay and Throughput. A. Average End-to-end Delay . D. Total Dropped Packets: The total number of dropped packets is the difference of number of packets sent by the source to the number of packets received by the destination mobile node. As the packets increases in the network, the load factor will be more on the network which leads in packet dropping _______________________________________________________________________________________ Volume: 02 Issue: 03 | May-2014, Available @ http://www.ijretm.com | Paper id - IJRETM-2014-02-03-409 4 International Journal of Research in Engineering Technology and Management ISSN 2347 - 7539 Wiley and Sons", 2007 ISBN 978-0-471-74300-2, pp. 203–209 [4]. Xu, Tian and Ansari, “Improving TCP performance in Integrated wireless communication networks”, ComputerNetworks, 2005. [5]. Changling Liu, Jörg Kaiser, "A Survey of Mobile Ad Hoc Network Routing Protocols", the University of Magdeburg, October 2005. 5. CONCLUSIONS This paper compared the popular ad hoc routing protocols AODV, DSR and DSDV Simulation results show that amongst all the protocols. The analysis of the obtained results shows that both AODV and DSR performs similar with small deviations. AODV has a stable End to End Delay despite mobility as it has the feature of On-Demand Routing protocol and also maintains a Routing table .DSDV has a higher Pdf than the other two routing protocols in mobility as it is a Table Driven protocol and is more reliable. DSR has the highest End to End Delay and Routing load increases the bandwidth and consuming the battery life. Based on the above simulation scenario, parameter, assumption and results AODV could be considered as an efficient faster routing protocol than DSR. . 6. ACKNOLGEMENT I would like to sincerely acknowledge the encourageous efforts of all faculty members and friends. Special thanks to our H.O.D. Dr. Ashish Bansal for giving me the opportunity to learn. [6]. 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