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Mobile Ad hoc Network is a set of mobile devices, which over a shared wireless medium communicate with each other without the presence of a predefined infrastructure or a central authority. The member nodes are themselves responsible for the creation, operation and maintenance of the network. Each node in the MANET is equipped with a wireless transmitter and receiver, with the aid of which it communicates with the other nodes in its wireless vicinity. The nodes which are not in wireless vicinity, communicate with each other hop by hop following a set of rules (routing protocol) for the hopping sequence to be followed.
The chief characteristics and challenges of the MANETs  can be classified as follows:
If the source node and destination node are out of range with each other then the communication between them takes place with the cooperation of other nodes such that a valid and optimum chain of mutually connected nodes is formed. This is known as multi hop communication. Hence each node is to act as a host as well as a router simultaneously.
Dynamism of Topology:
The nodes of MANET are randomly, frequently and unpredictably mobile within the network. These nodes may leave or join the network at any point of time, thereby significantly affecting the status of trust among nodes and the complexity of routing. Such mobility entails that the
Figure 2.1: A traditional base station scheme compared to an ad-hoc multi-hop network
topology of the network as well as the connectivity between the hosts is unpredictable. So the management of the network environment is a function of the participating nodes.
Lack of fixed infrastructure:
The absence of a fixed or central infrastructure is a key feature of MANETs. This eliminates the possibility to establish a centralized authority to control the network characteristics. Due to this absence of authority, traditional techniques of network management and security are scarcely applicable to MANETs.
MANETs are a set of mobile devices which are of low or limited power capacity, computational capacity, memory, bandwidth etc. by default. So in order to achieve a secure and reliable communication between nodes, these resource constraints make the task more enduring.
Figure. 1. A typical MANET
Albeit the security requirements (availability, confidentiality, integrity, authentication, non repudiation)  remain the same whether be it the fixed networks or MANETs, the MANETs are more susceptible to security attacks than fixed networks due their inherent characteristics. Securitizing the routing process is a particular challenge due to open exposure of wireless channels and nodes to attackers, lack of central agency/infrastructure, dynamic topology etc.. The wireless channels are accessible to all, whether meaningful network users or attackers with malicious intent. The lack of central agency inhibits the classical server based solutions to provide security. The dynamic topology entails that at any time any node whether legitimate or malicious can become a member of the network and disrupt the cooperative communication environment by purposely disobeying the routing protocol rules.
1.1 Routing Protocols in MANETs
The nodes in MANETs perform the routing functions in addition to the inherent function of being the hosts. The limitation on wireless transmission range requires the routing in multiple hops. So the nodes depend on one another for transmission of packets from source nodes to destination nodes via the routing nodes. The nature of the networks places two fundamental requirements on the routing protocols. First, it has to be distributed. Secondly, since the topology changes are frequent, it should compute multiple, loop-free routes while keeping the communication overheads to a minimum.
.1 Types of routing protocols.
Based on route discovery time, MANET routing protocols fall into three general categories:
a) Proactive routing protocols
b) Reactive routing protocols
c) Hybrid routing protocols
1.1.2 PROACTIVE ROUTING PROTOCOLS
Proactive MANET protocols are table-driven and will actively determine the layout of the network. The complete picture of the network is maintained at every node, so route selection time is minimal. But the mobility of nodes if high then routing information in the routing table invalidates very quickly, resulting in many short lived routes. This also causes a large amount of traffic overhead generated when evaluating these unnecessary routes. For large size networks and the networks whose member nodes make sparse transmissions, most of the routing information is deemed redundant. Energy conservation being very important in MANETs, the excessive expenditure of energy is not desired. Thus, proactive MANET protocols work best in networks that have low node mobility or where the nodes transmit data frequently. Examples of proactive MANET protocols include Optimized Link State Routing (OLSR) .
1.1.3 REACTIVE ROUTING PROTOCOLS
Reactive MANET protocols only find a route to the destination node when there is a need to send data. The source node will start by transmitting route requests throughout the network. The sender will then wait for the destination node or an intermediate node (that has a route to the destination) to respond with a list of intermediate nodes between the source and destination. This is known as the global flood search, which in turn brings about a significant delay before the packet can be transmitted. It also requires the transmission of a significant amount of control traffic. Thus, reactive MANET protocols are most suited for networks with high node mobility or where the nodes transmit data infrequently. Examples of reactive MANET protocols include Ad Hoc On-Demand Distance Vector (AODV) , Dynamic Source Routing (DSR) , Temporally Ordered Routing Algorithm (TORA) , and Dynamic MANET on Demand (DYMO) .
1.1.4 HYBRID ROUTING PROTOCOLS
Since proactive and reactive routing protocols each work best in oppositely different scenarios, there is good reason to develop hybrid routing protocols, which use a mix of both proactive and reactive routing protocols. These hybrid protocols can be used to find a balance between the proactive and reactive protocols. The basic idea behind hybrid routing protocols is to use proactive routing mechanisms in some areas of the network at certain times and reactive routing for the rest of the network. The proactive operations are restricted to a small domain in order to reduce the control overheads and delays. The reactive routing protocols are used for locating nodes outside this domain, as this is more bandwidth-efficient in a constantly changing network.
1.2 Protocols used in MANETs
AODV (Ad hoc On-demand Distance Vector)
AODV is an on-demand routing protocol. The AODV algorithm gives an easy way to get change in the link situation. For example if a link fails notifications are sent only to the affected nodes in the network. This notification cancels all the routes through this affected node. It builds unicast routes from source to destination and that's why the network usage is least. Since the routes are build on demand so the network traffic is minimum. AODV does not allow keeping extra routing which is not in use . If two nodes wish to establish a connection in an ad hoc network then AODV is responsible to enable them to build a multi-hop route. AODV uses Destination Sequence Numbers (DSN) to avoid counting to infinity that is why it is loop free. This is the characteristic of this algorithm. When a node send request to a destination, it sends its DSNs together with all routing information. It also selects the most favorable route based on the sequence number .
There are three AODV messages i.e. Route Request (RREQs), Route Replies (RREPs), and Route Errors (RERRs) . By using UDP (user datagram protocol) packets, the source to destination route is discovered and maintain by these messages. For example the node which request, will use its IP address as Originator IP address for the message for broadcast. It simply means that the AODV not blindly forwarded every message. The number of hops of routing messages in ad hoc network is determined by Time-To-Live (TTL) in the IP header.
When the source node wants to create a new route to the destination, the requesting node broadcast an RREQ message in the network . In the figure 1.3 the RREQ message is broadcasted from source node A to the destination node B. The RREQ message is shown by the black line from source node A to many directions. The source node A broadcasts the RREQ message in the neighbor nodes. When the neighbor nodes receive the RREQ message it creates a reverse route to the source node A. This neighbor node is the next hop to the source node A. The hop count of the RREQ is incremented by one. The neighbor node will check if it has an active route to the destination or not. If it has a route so it will forward a RREP to the source node A. If it does not have an active route to the destination it will broadcast the RREQ message in the network again with an incremented hop count value. The figure 1.3 shows the procedure for finding the destination node B. The RREQ message is flooded in the network in searching for finding the destination node B. The intermediate nodes can reply to the RREQ message only if they have the destination sequence number (DSN) equal to or greater than the number contained in the packet header of RREQ.
The intermediate nodes forward the RREQ message to the neighbor nodes and record the address of these nodes in their routing cache. This information will be used to make a reverse path for RREP message from the destination node, it is shown in the below figure 1.3. The destination node B replies with RREP message denoted by the dotted orange line, the shortest path from destination B to source A. The RREP reached to the originator of the request. This route is only available by unicasting a RREP back to the source. The nodes receiving these messages are cached from originator of the RREQ to all the nodes.
When a link is failed an RERR message is generated. RERR message contains information about nodes that are not reachable. The IP addresses of all the nodes which are as their next hop to the destination.
All the routing information about the network is stored in the table. The routing table have these route entries; (i) destination IP address, (ii) Destination Sequence Number (DSN), (iii) Valid Destination Sequence Number flag (iv) other state and routing flags (e.g., valid, invalid, repairable being repaired) (v) network interface (vi) hop count (number of hops needed to reach destination) (vii) next hop (viii) the list of precursors and lifetime (Expiration time of the route).
Figure 1.3: RREQ and RREP messages in MANET using AODV
In AODV routing mechanism, the AODV protocol first broadcasts RREQ packet in order to discover the paths required by a source node to destination node as shown in Figure 1.4. In response, once the RREQ packet reaches the destination or an intermediate node (any node on the route between the source and destination node) with a fresh enough route to destination node, the destination or intermediate node responds by unicasting a route reply (RREP) packet as shown in Figure 1.5. Once the source node receives the RREP packet, it starts sending its data packets through the route enclosed within the RREP packet.
Figure 1.4: Propagation of route request (RREQ).
Figure 1.5: The path of a routing reply (RREP).
Routing Attacks in MANETs
All of the routing protocols in MANETs depend on active cooperation of nodes to provide routing between the nodes and to establish and operate the network. The basic assumption in such a setup is that all nodes are well behaving and trustworthy. Albeit in an event where one or more of the nodes turn malicious, security attacks can be launched which may disrupt routing operations or create a DOS (Denial of Service) condition in the network.
Due to dynamic, distributed infrastructure less nature of MANETs, and lack of centralized authority, the ad hoc networks are vulnerable to various kinds of attacks. The challenges to be faced by MANETs are over and above to those to be faced by the traditional wireless networks. The accessibility of the wireless channel to both the genuine user and attacker make the MANET susceptible to both passive eavesdroppers as well as active malicious attackers. The limited power backup and limited computational capability of the individual nodes hinders the implementation of complex security algorithms and key exchange mechanisms. There is always a possibility of a genuine trusted node to be compromised by the attackers and subsequently used to launch attacks on the network. Node mobility makes the network topology dynamic forcing frequent networking reconfiguration which creates more chances for attacks.
The attacks on MANETs can be categorized as active or passive. In passive attacks the attacker does not send any message, but just listens to the channel. Passive attacks are non disruptive but are information seeking, which may be critical in the operation of a protocol. Active attacks may either be directed to disrupt the normal operation of a specific node or target the operation of the whole network. A passive attacker listens to the channel and packets containing secret information (e.g., IP addresses, location of nodes, etc.) may be stolen, which violates confidentiality paradigm. In a wireless environment it is normally impossible to detect this attack, as it does not produce any new traffic in the network.
The action of an active attacker includes; injecting packets to invalid destinations into the network, deleting packets, modifying the contents of packets, and impersonating other nodes which violates availability, integrity, authentication, and non repudiation paradigm. Contrary to the passive attacks, active attacks can be detected and eventually avoided by the legitimate nodes that participate in an ad hoc network . In , the authors have surveyed attacks on
MANETs and their countermeasures on protocol layer wise criteria. In , B.Kannhavong et al. have surveyed newer attacks like flooding, black hole, link with holding, link spoofing, replay, wormhole, colluding misrelay and their countermeasures. In ,  the authors have presented an overview of secure routing protocols (Authenticated routing for ad hoc networks (ARAN), Ariadne, Secure AODV (SAODV), Secure Efficient Ad hoc Distance vector routing protocol (SEAD), Secure Routing Protocol (SRP), Secure Link-State Protocol (SLSP) ) in MANETs. Following are the well known routing attacks in MANETs.
Flooding Attack : Routing Table Overflow:
The attacker node floods the network with bogus route creation packets to fake (non-existing) nodes or simply sends excessive route advertisements to the network. The purpose is to overwhelm the routing-protocol implementations, by creating enough routes to prevent new routes from being created or to overwhelm the protocol implementation. Proactive routing protocols, as they create and maintain routes to all possible destinations are more vulnerable to this attack.
Black Hole Attack:
MANET attacks are categorized according to their emission into two main categories: passive attacks, and active attacks. In passive attacks, the intruder only performs some kind of monitoring on certain connections to get information about the traffic without injecting any fake information, e.g. an eavesdropping attack. In active attacks, the intruder performs an effective violation on either the network resources or the data transmitted; this is done by causing routing disruption, network resource exhaustion, and node breaking. One of the dangerous active attacks is the BHA . BHA in MANETs is a serious security problem to be solved, in which the attacker injects false routing information in the received routing packets in order to advertise itself as having the best route to the destination. If the attacker in BHA succeeds in gaining the route, it can intercept the coming and perform eavesdropping, denial-of-service, or man-in-the-middle attacks. For example, in Figure 1.6, node N1 wants to send data packets to node N6 and initiates the route discovery process. We assume node N2 to be an attacker node with no fresh enough route information to the destination node N6. However, node N2 claims directly that it has the route to the destination whenever it receives RREQ packet from node N1 and sends the RREP packet response directly to source node N1. In this case, the node N2 forms a black hole in the network. Node N2can easily misroute the network traffic to itself and cause an attack to the network.
Figure 1.6: The black hole attack.
In order to fake AODV using BHA, the attacker may use one of the two methods:
· sending a RREP packet towards the source node with a high enough sequence number.
· sending a RREP packet to the source node with a small enough hop count number.
In most cases, the BHA attacker gains the route if the routing protocol does not protect itself. This is because the BHA attacker does not follow the routing protocol rules by responding directly to the source node. Hence, the BHA attacker replies quicker than the real destination node or any other nodes in the network.
As MANET has dynamic topology, no centralized monitoring and limited physical security so it is more vulnerable to attacks and one of them is Black Hole Attack which in turns made difficult to decrease the overhead for whole network.
Particularly in Protocols like AODV in which overhead is more and if it is attacked by some sort of attack like Worm hole or Black hole. So some solutions are proposed to avoid these types of attacks which include traditional multipath algorithms. Due to large deployment of applications in different specific networks, black hole attacks increased exponentially which produces difficult results to handle.
Routing Table Poisoning Attack:
Different routing protocols maintain tables which hold information regarding routes of the network. In poisoning attacks, the attacker node generates and sends fictitious traffic, or mutates legitimate messages from other nodes, in order to create false entries in the tables of the participating nodes. Another possibility is to inject a RREQ packet with a high sequence number.
This causes all other legitimate RREQ packets with lower sequence numbers to be deleted . Routing table poisoning attacks can result in selection of non optimal routes, creation of routing loops, bottlenecks and even partitioning certain parts of the network.
The wormhole attack involves the cooperation between two attacking nodes . One attacker captures routing traffic at one point of the network and tunnels it to another point in the network that shares a private high speed communication link between the attackers, and then selectively injects tunnel traffic back into the network. The two colluding attacker can potentially distort the topology and establish routes under the control over the wormhole link.
Location Disclosure Attack:
In this attack, the privacy requirements of an ad hoc network are compromised. Through the use of traffic analysis techniques or with simpler probing and monitoring approaches an attacker is able to discover the location of a node, and the structure of the network.
Rushing Attacks :
The attacker (initiator) node initiates a Route Discovery for the target node. If the ROUTE
REQUESTs for this Discovery forwarded by the attacker are the first to reach each neighbor of the target, and then any route discovered by this Route Discovery will include a hop through the attacker. That is, when a neighbor of the target receives the rushed REQUEST from the attacker, it forwards that REQUEST, and will not forward any further REQUESTs from this Route Discovery. When non attacking REQUESTs arrive later at these nodes, they will discard those legitimate REQUESTs. As a result, the initiator will be unable to discover any usable routes (i.e., routes that do not include the attacker) containing at least two hops (three nodes).
The attack incurs due to lack of authenticity and it grants provision for any node to corrupt other node's legitimate information. Nodes usually keep information of perceived malicious nodes in a blacklist. This attack is relevant against routing protocols that use mechanisms for the identification of malicious nodes and propagate messages that try to blacklist the offender. An attacker may fabricate such reporting messages and tell other nodes in the network to add that node to their blacklists and isolate legitimate nodes from the network .
Solutions for attacks
Multipath Routing Algorithm:
In MANET, all the nodes in the networks are equity, and functions as terminal as well router. There is difference in performance instead of function. The main advantage of the structure is that there are multiple paths between source-destination pairs. So it can distribute traffic into multiple paths, decrease congestion and eliminate possible "bottleneck". But MANET with the plane structure will increase routing control overhead, the scalability problem is likely to happen.
Utilizing clustering algorithm to construct hierarchical topology may be a good method to solve these problems. An adaptive mobile cluster algorithm can sustains the mobility perfectly and maintains the stability and robustness of network architecture.
To support the multi hop and mobile characteristics of wireless ad hoc network, the rapid deployment of network and dynamic reconstruction after topology changes are effectively implemented by clustering management. Clustering management has five outstanding advantages over other protocols. First, it uses multiple channels effectively and improves system capacity greatly. Second, it reduces the exchange overhead of control messages and strengthens node management. Third, it is very easy to implement the local synchronization of network. Fourth, it provides quality of service (QoS) routing for multimedia services efficiently. Finally, it can support the wireless networks with a large number of nodes.
Review of Literature
E. A .Mary Anita, V. Vasudevan, in 2010  explains the security in wireless ad-hoc networks. They propose a certificate basedauthentication mechanism to counter the effect of black holeattack. Nodes authenticate each other by issuing certificates to neighboring nodes and generating public key without the need ofany online centralized authority. The proposed scheme isimplemented in two phases: certification phase and authentication phase following the route establishment process of On DemandMulticast Routing Protocol (ODMRP). Simulations show thatBHS-ODMRP is as effective as ODMRP in discovering andmaintaining routes in addition to providing the required security. They proposed some good explanation and solution to avoid black hole attacks.
Rajpal Singh Khainwar, Mr. Anurag Jain, Mr. Jagdish Prasad Tyagi,in 2011  elaborates the multipath algorithm with performance evaluation and elimination of wormhole attacker node in MANET.They explained that more security is required in comparison to wired network. Wireless networks are susceptible to many attacks, including an attack known as the wormhole attack. The wormhole attack is very powerful, and preventing the attack has proven to be very difficult. In wormhole attacks, one malicious node tunnels packets from its location to the other malicious node. Such wormhole attacks result in a false route with fewer. If source node chooses this fake route, malicious nodes have the option of delivering the packets or dropping them. Theyspecifically consider Wormhole attack. Instead of detecting suspicious routes as in previous methods and they implement a new method which detects malicious nodes and works without modification of protocol, using a hop-count and time delay analysis from the user's point of view without any special environment assumptions. The proposed work is simulated using OPNET and results showing the advantages of proposed work.
H. A. Esmaili, M. R. KhaliliShoja, Hosseingharaee, in 2011  elaborates theMobile ad hoc networks (MANETs) are dynamic wireless networks without any infrastructure. These networks are weak against many types of attacks. One of these attacks is the black hole. In this attack, a malicious node advertises itself as having freshest or shortest path to specific node to absorb packets to itself. The effect of black hole attack on ad hoc network using AODV as a routing protocol will be examined in this research. Furthermore, they investigate solution for increasing security in these networks. Simulation results using OPNET simulator depict that packet delivery ratio in the presence of malicious nodes, reduces notably.
EktaKamboj, Harish Rohil, in 2011  explains that mobile ad-hoc network which dynamically set up temporary paths between mobile nodes which acts both as router and hosts to send and receive packets. As MANET has dynamic topology, no centralized monitoring and limited physical security so it is more vulnerable to attacks and one of them is Black Hole Attack. This attack can be easily implemented in AODV during the routing discovery process. In the Black Hole attack, a malicious node impersonates as destination node either by showing highest destination sequence number or by advertising itself as having the shortest path to destination node. Once the forged route has been established the malicious node is able to become a member of the active route and intercept all communication packets across that node. An intrusion detection system is introduced to detect Black Hole Attack on AODV in MANET using fuzzy logic. This IDS uses two factors that is forward packet ratio and destination sequence number. These factors are implemented using fuzzy logic in which fidelity level is checked and compared against threshold value and detected whether there is black hole attack or not. The proposed IDS have been tested using NS2.
DrKarimKonate, Abdourahime Gaye, in 2011 done work dedicated to study attacks and countermeasure in MANET. After a short introduction to what MANETs are and network security they present a survey of various attacks in MANETs pertaining to fail routing protocols. They present the different tools used by these attacks and the mechanisms used by the secured routing protocols to counter them. They also study a mechanism of security, named the reputation, proposed for the MANETs and the protocol which implements it as well as its vulnerabilities. This work ends with a proposal to fend off some of these attacks like Blackhole cooperative, Blackmail, Overflow, Selfish and an implementation of this solution on a compiler of C named Dev.-C++ in order to make comparative tests with the mechanisms already proposed.
Inferences drawn from literature survey
After reviewing many papers we found that MANET has dynamic topology, no centralized monitoring and limited physical security so it is more vulnerable to attacks and one of them is Black Hole Attack. This attack can be easily implemented in AODV during the routing discovery process. In the Black Hole attack, a malicious node impersonates as destination node either by showing highest destination sequence number or by advertising itself as having the shortest path to destination node. Many solutions are there for solving but due to dynamic nature these problems kept on rising and need more solutions accordingly. We can introduce some better multipath routing solution for Blackhole attack in MANET.
MANET is a mobile ad-hoc network which dynamically set up temporary paths between mobile nodes which acts both as router and hosts to send and receive packets. As MANET has dynamic topology, no centralized monitoring and limited physical security so it is more vulnerable to attacks and one of them is Black Hole Attack. In Black hole attack a malicious node makes use of the vulnerabilities of the route discovery packets of the routing protocol to advertise it as having the shortest path to the node whose packets it wants to intercept . This attack can be easily implemented in AODV during the routing discovery process. In the Black Hole attack, a malicious node impersonates as destination node either by showing highest destination sequence number or by advertising itself as having the shortest path to destination node. Once the forged route has been established the malicious node is able to become a member of the active route and intercept all communication packets across that node. Our research will focus on providing solution for this problem by enhancing multipath algorithm by integrating it with two factors that is forward packet ratio and destination sequence number. These factors will be implemented using existing multipath algorithm which can prevent black hole attacks in MANET networks.
To have a performance evaluation of AODV using HTTP traffic under black hole attack in MANET.
To achieve better solution for avoiding the black hole attack in Mobile Ad-hoc Network.
To simulate the Mobile Ad-hoc Network under attack and implement solutions for it in OPNET Simulator.
Our research will focus providing better solutions for prevention of black hole attack in MANET networks.We will start with simple multipath algorithm with factors like forward packet ratio and destination sequence number for Ad-hoc on demand protocol. We will do our implementation in Following Phases:
1st Phase: This phase will contain the basic functionality and layout of network using servers and ad-hoc devices.
2nd Phase: In this phase, we will implement the different tasks to network by configuring the task management through task manger in OPNET. After configuring tasks, we will configure the traffic type i.e. FTP and HTTP. After all configurations of applications, finally we will configure the profile for different scenarios.
3rd Phase: In this phase, we will put some malicious nodes into implemented networks with different scenarios containing variation in number of mobile nodes.
4th Phase: We will implementmultipath algorithm with some changes as discussed earlier.
5th Phase: We will finally analyze the results by removing black hole attack and by comparing our proposed scheme to some simple network.
There are different kinds of parameters for the performance evaluation of the AODV routing protocol. These have different behaviors of the overall network performance. We have evaluated three parameters for the comparison of our study on the overall network performance. These parameters are delay, network load, and throughput for protocols evaluation. These parameters are important in the consideration of evaluation of the routing protocols in a communication network. AODV protocol needs to be checked against certain parameters for their performance under black hole attacks. To check protocol effectiveness in finding a route towards destination, we have looked to the source that how much control messages it sends. It gives the routing protocol internal algorithm's efficiency. If the routing protocol gives much end to end delay so probably this routing protocol showing bad effects due to the black hole attacks. Overall, these parameters shows the variation of AODV updates and routing with respect to normal AODV routing, AODV routing with single black hole attack, AODV routing with two black hole attacks and AODV routing with three black hole attacks.
The packet delay is the time of creation of a packet by the source node up to the destination node reception. At this time a packet starts to move across the working network. Time usually expressed in seconds. Hence all the delays in the network are called packet end-to-end delay, like buffer queues and transmission time. This delay can be called as latency; it provides same sense as delay. Some applications are sensitive to packet delay such as voice is a delay sensitive application. Voice has a low average delay in the network. The HTTP is can compromise certain amount of delays. There are different kinds of activities because of which network delay is increased. Packet end-to-end delay is a measure of how sound a routing protocol adapts to the various constraints in the network to give reliability in the routing protocol . We have several kinds of delays which are processing delay (PD), queuing delay (QD), transmission delay (TD) and propagation delay (PD) . The queuing delay (QD) is not included, as the network delay has no concern with it .
6.2 Network Load
Network load represents the total load in bit/sec submitted to wireless LAN layers by all higher layers in all WLAN nodes of the network . When there is more traffic coming on the network, and it is difficult for the network to handle all this traffic so it is called the network load . The efficient network can easily cope with large traffic coming in, and to make a best network, many techniques have been introduced .
High network load affects the MANET routing packets and slow down the delivery of packets for reaching to the channel , and it results in increasing the collisions of these control packets. Thus, routing packets may be slow to stabilize. Network load is shown in the below figure 6.1.
Fig 6.1: Network Load Description
Throughput is defined as; the ratio of the total data reaches a receiver from the sender. The time it takes by the receiver to receive the last message is called as throughput . Throughput is expressed as bytes or bits per sec (byte/sec or bit/sec). Some factors affect the throughput as; if there are many topology changes in the network, unreliable communication between nodes, limited bandwidth available and limited energy . A high throughput is absolute choice in every network.
6.4 Software Environment
We are using the Optimized Network Engineering Tool (OPNET v14.0) software for our simulations. OPNET is a network simulator. It provides multiple solutions for managing networks and applications e.g. network operation, planning, research and development (R&D), network engineering and performance management. OPNET 14.0 is designed for modeling communication devices, technologies, protocols and to simulate the performance of these technologies.
OPNET Technologies provides solutions for the academic research, for example assessment and improvement of wireless network technologies such as WiMAX (Worldwide Interoperability for Microwave Access), Wi-Fi, UMTS (Universal Mobile Telecommunications System) and seamless communication. Design and assessment of MANET protocols, analysis of optical network, and enhancement in the core network technologies such as IPv6, MPLS, and power management schemes in wireless sensor network . Now a day OPNET is very useful software in research fields. The OPNET usability can be divided into four main steps. The OPNET first step is the modeling, it means to create network model. The sec step is to choose and select statistics. Third step is to simulate the network. Fourth and last step is to view and analyze results.