Proactive and Reactive MANET Protocols Analysis
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Published: Mon, 12 Feb 2018
Ad hoc network
A mobile ad hoc network (MANET) is consisting of wireless mobile nodes. The communication of these mobile nodes is carried out without any centralized control. Routing is a critical issue in MANET. The focus of this thesis is on the performance of routing protocols. We compare three routing protocols in MANET i.e. AODV, DSR and OLSR. OPNET is the simulation tool. These routing protocols performance are analyzed by three important metrics: delay, network load and throughput. All the three routing protocols are explained in a deep way with metrics. The comparison analysis will be carrying out about these protocols and in the last the conclusion will be present. That which routing protocol is the best for mobile ad hoc network.
MANET stands for Mobile Ad hoc Network. A decentralized autonomous wireless system which consists of free nodes. MANET sometimes called mobile mesh network. MANET is a self configurable wireless network. A MANET consists of mobile nodes, a router with multiple hosts and wireless communication devices. The wireless communication devices are as transmitters, receivers and antennas. These antennas can be of any kind. These nodes can be fixed or mobile. The term node referred to as, which are free to move arbitrarily in every direction. These nodes can be a mobile phone, laptop, personal digital assistance, MP3 player and personal computer. These nodes located, might be in cars, ships, airplanes or with people having small electronic devices . Nodes can connect to each other randomly and forming arbitrary topologies. Nodes communicate to each other and also forward packets to neighbor nodes as a router. The ability of self configuration of these nodes makes them more suitable for urgently required network connection. For example in disaster hit areas where there is no communication infrastructure. It is greatly desired to have a quick communication infrastructure. MANET is the quick remedy for any disaster situation. The word Ad hoc means ‘For a special purpose’. So MANET a spontaneous network is useful when dealing with wireless devices in which some of the devices are part of the network only for the duration of a communication session and the need for a dynamic network topology is prominent. The MANET working group (WG) within the Internet Engineering Task Force (IETF) working specifically on developing IP routing protocols topologies. In order to improve mobile routing and interface definition standards for use within the Internet protocol suite .
After huge research work on MANET, still MANET does not have complete formed Internet based standards. The identification of experimental Request For Comments (RFCs) since 2003  is used. In these RFCs the questions are unanswered concerning of implementation or deployment of these routing protocols. But these proposed algorithms are identified as a trial technology and there is a high chance that they will develop into a standard . Extensive research work in this area has continued since then with major studies on different routing protocols such as Ad hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR), Temporarily Ordered Routing Algorithm (TORA) and Optimized Link State Routing (OLSR) . Also on the standardization of routing and interface solutions for mobile networking support through Internet Engineering Task Force (IETF) Mobile Ad hoc network (MANET) Working Group WG .
Aims and Objectives
There are two groups of routing protocols. Proactive MANET protocol, Reactive MANET Protocol, and the third are derived from both called Hybrid MANET Protocol. The Proactive MANET protocol is generally called table driven protocol. It detects the network layout periodically. It tries to maintain the routing table at every node. From which a route to the destination from the source can be detected with less delay. Proactive MANET protocols provide good reliability and low latency for deciding a route. Proactive MANET protocol is not suitable for the node moving with high speed. The routing information in the routing table cannot be updated in the routing table. If a node is not moving, then its routing table information is updated continuously. It makes much traffic overhead and also waste network resources as bandwidth . Proactive MANET protocol is also not suitable for large scale MANETs.
Whereas Reactive MANET Protocol is called on-demand routing protocol. Reactive MANET Protocol finds the route when a source node requests to communicate with the other. On-demand approach is suitable for the nodes with high mobility. Nodes that transmit data rarely. The main drawback of reactive routing protocols is that the source node broadcasts the routing requests in the whole network. Then it waits for the responses. This route discovery procedure produces significant delay .
Hybrid MANET Protocol integrates the merits of Proactive MANET protocol and Reactive MANET Protocol. Zone routing protocol (ZRP) and two zone routing protocols is the example of hybrid of MANET protocol.
Our goal in this Masters thesis is to evaluate the performance of Proactive and Reactive MANET protocols. These protocols have different behaviors for wireless routing aspects. The main problem is to choice the correct and efficient routing protocol for MANET. The main questions arise for the evaluation of these problems.
First question is which routing protocol provides a better performance in Mobile Ad hoc Networks? This will give the overall performance of each routing protocol. Second question is what factors influence the performance of these routing protocols? Finally we address the main key differences in these routing protocols. To answer all these questions, we will model some of MANET scenarios with different parameters. To evaluate the performance of Proactive MANET protocol and Reactive MANET Protocols as, AODV, DSR and OLSR with respect to some parameters as delay, network load and throughput. In simulating these scenarios we come to know that no single routing protocol among Proactive MANET protocol and Reactive MANET Protocol is superior in terms of overall network performance. For example one protocol is good in average delay while other is best in network load and throughput. The performance of these routing protocols greatly depends on network load and delay. So the best protocol can give low delay and high throughput.
Scope of the thesis
As we know the two categories of routing protocols. Reactive, proactive, and the derived one from reactive and proactive protocols are referred to as hybrid routing protocol. The hybrid protocol is a combination of both reactive and proactive routing protocols. In this thesis, we considered three routing protocols. Two of them are reactive protocols i.e. AODV and DSR. One of them is proactive protocol i.e. OLSR. In this thesis we evaluate the behavior of these routing protocols when implemented in the network. We look that how these protocols affect the network performance, and how the routing protocols behave in these networks. There is no need to go in depth the design of these routing protocol algorithms. But we will give a detailed explanation of these routing protocols. That we are able to explain their effects on the network. We did not consider the effects of varying pause time of the mobile nodes in our simulations. These pause time will be kept constant in all the scenarios. Energy consumption of the routing protocol algorithms was also not considered in the thesis.
The thesis is mainly divided into six chapters. Chapter 1 introduces the topic. In this chapter we discuss the MANET with detail, and also the research question. Chapter 2 presents the background of our work. Types of wireless networks and some part of related work with example. Chapter 3 gives the state of the art. It gives the full theoretical background and concepts of the ad hoc mobile network routing protocols i.e. reactive MANET protocols and proactive MANET protocols. Chapter 4 is about the performance metrics: delay, network load and throughput and also about the simulation tool OPNET Modeler 14.5. Chapter 5 gives the results and an analysis of all the routing protocols simulated. In chapter 6, the conclusion and future work is presented.
Chapter 2 Background and Related Work
In this chapter we present the background of our work. Types of wireless networks and some part of related work with example.
MANET have a dynamic nature, a large number of applications make them ideal to use. Quick deployment and minimal configuration of MANET in emergencies such as natural disaster makes them more suitable. The growth of technology makes increase in Wi-Fi capable laptops, mobile phones, MP3 players and other small portable devices. Hence a reason for MANET popularity.
Extensive research work has been done on the performance evaluation of routing protocols using NS2 network simulator. Different methods and simulation environments give different results for MANET routing protocols performance. We need to look in a broader view for the effects of these routing protocols which are not considered in a specific environment. The theme of this project is to evaluate the performance of Proactive MANET protocols (PMP) and Reactive MANET Protocols (RMP) in OPNET Modeler 14.5 under varying network load . For all these comparisons we will use FTP traffic to look the effects of the ad hoc network protocols. The project goal is to give an extra source of comparison statistics in the research field. In our simulation we have wireless routing protocols carrying FTP traffic. These simulations performed will have a strong link with the theoretical concepts and also with the expected performance in practical implementations. This study work will give a great benefit in the future research work.
Extensive research works has been done in the field of MANET routing protocols. Different routing protocols were simulated in different kind of simulators. Here we will discuss different research papers on the performance of MANET routing protocols. In this thesis work we simulate three MANET routing protocols in the OPNET modeler 14.5. AODV, DSR and OLSR were simulated against three different parameters i.e. delay, network load and throughput. The results show that OLSR is best in network delay than AODV and DSR. The protocols best in the network delay must be the finest in the network throughput. Below we will study now different simulators with different routing protocols and their performance.
These routing protocols DSDV, AODV, DSR and TORA were simulated using NS2 . Analysis gives different results for every parameter differently. In finding shortest path between the source and destination nodes, delay, DSDV performs well than AODV, DSR and TORA. DSR perform well in network load balancing than DSDV, AODV and TORA. DSDV has good jitter than AODV, TORA and DSR respectively. The results given in  analyse DSR and DSDV in idealized and realistic simulation environments on their performance. Another paper in reference  gives conclusion in mobile ad hoc network that reactive protocols i.e. AODV and DSR perform well when the network load is moderate. In reference  the reactive protocols are saving much resource like energy. It analyse that the proactive protocols perform well in heavy network traffic load.
In  there are different conclusions about the MANET routing protocols. DSDV, AODV and DSR were simulated in NS2. The reactive protocol AODV outperforms than DSDV and DSR in maintaining connection by sequentially exchange of information for TCP based traffic. The packets are delivered when the node mobility is low and failed to deliver at high mobility. DSR perform well than DSDV at all mobility. In  DSR perform well than DSDV and AODV for packet dropping rate (PDR), delay and throughput. DSR generates less network load than AODV.
In reference , the simulation was done in QUALNET simulator. The author wrote that AODV shows best performance in low and medium node density. Where as in high node density both OLSR and DSR outperforms. The author wrote in , that DSR is selected for file transfers where delivery and throughput are critical factors. OLSR performs well in both low and high node density. It is stated in  that OLSR is best suited in application oriented traffic e.g. streaming traffic, voice and video traffic. In application based traffic delay is a critical factor.
Types of Wireless Networks
Before we discuss the wireless networks types, a small difference between wired and wireless network is discussed. A network that sends data from one point to another point with cable or wire is called wired network. The data sent over a network which uses wireless medium from one device to another device is called wireless network. In wireless network data is transmitted from one point to another through wireless links. For communication the devices have to be in the transmission or radio range of each other. Wireless networks are divided into two main groups. First infrastructure wireless network and second is Ad hoc or infrastructure-less network.
Fixed network topology is deployed in infrastructure network. These deployed, fixed networks have base stations or access points from which wireless nodes can get connected. All the base stations or access points are connected with the main network through wired links (fiber optic, twisted or coaxial cable) or wireless link. The base station or access point is one of the important units of infrastructure networks. All of the connections will have to pass from the access point. A wireless node can connect to anyone of the access points in its range.
Ad hoc Networks
An Ad hoc network is deployed where wireless network infrastructure is not available. This kind of ad hoc network is called infrastructure less network. In ad hoc network each node is connected through wireless links. These nodes connected to each other and also act as a router, by forwarding data to other nodes. There is no restriction on these nodes to join or leave the network. Thus the network has no vital infrastructure. Ad hoc networks have two forms; one is static ad hoc networks (SANET), the other is called mobile ad hoc network (MANET). Commercial implementation of ad hoc network becomes possible due to the development of new technology such as 802.11 .
The main reason to deploy this kind of network is the flexibility and easiness of deployment. A suitable network for emergency and surveillance use. But with all these qualities, ad hoc network operation is very difficult to handle. Each and every node is responsible for its operation to maintain its routing table and also forwarding packets to its neighbors as routers. MANET has different topology changes while deployed. So ad hoc network need an efficient routing protocol. To construct an efficient routing protocol is a tough and tedious task.
Mobile Ad hoc Networks
As mentioned before an ad hoc network is a wireless network, which do not have a centralized and fixed infrastructure. MANET is referred to a wireless ad hoc network. In which nodes are free to move arbitrarily. In a MANET, mobile nodes transmit and receive the traffic. Also mobile nodes can act like routers by forwarding the neighbors traffic to the destination. As the routers are mostly multi hops . MANET does not need base stations of wired infrastructure. The mobile nodes in wireless network range can communicate with each other. MANET is self organized network. The mobile nodes form a network automatically without a fixed infrastructure and central management . The mobile nodes have transmitters and receivers with smart antennas, which enable the mobile nodes to communicate with other mobile nodes in the network. The topology of the network change every time by getting in and out of the mobile nodes in the network. In the beginning MANET was designed for military use but now the MANET is used in many areas. Such as in disaster hit areas, data collection in some region, in rescue missions, virtual classes and conferences . This concept with ad hoc network makes the full name of mobile ad hoc network (MANET). By growing the network, combined with the node mobility. The challenges of self configuration of the network become more evident. Security in the MANET is a very important issue. Many techniques were defined for the security of MANET. Intrusion detection technique is investigated in reference . Mobile nodes in the network waste much energy by joining in and out with connection to wireless network. This connection and reconnection create energy limitation in the network.
The main purpose of developing the ad hoc routing protocols to cope with the dynamic nature of MANET. The routing protocols efficiency can be determined by the battery power consumption. Energy is consumed during participation of a node in a network and also in routing of traffic. The routing protocol which adapts to the connection tearing and mending is also considered vital. Such routing protocols are AODV, DSR and OLSR, TORA, Wireless Routing Protocol (WRP), Zone Routing Protocol, and Two-Zone Routing Protocol (TZRP) . We will discuss reactive and proactive routing protocols i.e. AODV, DSR and OLSR in chapter 3 respectively. The internet engineering task force (IETF) MANET working group (WG) was dedicated to standardize the routing protocols in MANET. RFC 2501 specifies the charter of the working group .
An Example of MANET Application
The versatility and self configuration of MANET makes them a best choice for a wide range of applications. MANET can be used in natural disaster areas, pre planed strategic event like surveillance, data collecting in some regions, conferences and virtual classes. In such areas where the fixed infrastructure is not available before. Like earthquake hit areas where the fixed infrastructure has been destroyed, in flooded areas, fire or explosion hit areas, train or air plane crash . A very common use of MANET is during business conferences. The only and key attribute that make MANET ideal is their self configuration and low cost of deployment.
Here we will present one practical example. In a virtual class, a WiMAX radio link may be established. Then a MANET access network can be established to give coverage to those areas that is difficult to cover. The nodes far away from the base station rely on midway nodes for communication. Thus provide a best communication network in such hostile situation. Above in figure 1, a deployed MANET over WiMAX backbone is shown. In this figure the mobile nodes and the WiMAX_WLAN Router form a MANET. These nodes are connected to the WiMAX_WLAN router and the router is further connected to the WiMAX network. The router is working like a boundary between the MANET and the WiMAX. The WiMAX_WLAN router is capable of translation between the MANET protocols and the WiMAX network protocols, and also the backbone protocols the WiMAX is connected with. The figure 1 is shown above.
Chapter 3 Ad hoc Networks Routing Protocols
The theoretical concepts of ad hoc routing protocols are discussed in this chapter. The behaviors of proactive and reactive routing protocols will be analyzed.
Routing means to choose a path. Routing in MANET means to choose a right and suitable path to the destination from the source. Routing terminology is used in different kinds of networks. In telephony technology, electronic data networks and in the internet network, the term routing is used. Here we are more concern about routing in mobile ad hoc networks. Routing protocols in mobile ad hoc network means that the mobile nodes will search for a route or path to connect to each other and share the data packets. Protocols are the set of rules through which two or more devices (mobile nodes, computers or electronic device) can communicate to each other. In mobile ad hoc networks the routing is mostly done with the help of routing tables. These tables are kept in the memory cache of these mobile nodes. When routing process is going on, it route the data packets in different mechanisms. The first is unicast, in which the source directly sends the data packets to the destination. The second is broadcast; it means the source node sends messages to all the near and far nodes in the network. The third is anycast, in this the source node sends data packet to anyone which is not in the node group.
Routing has two basic types, which are as under
- Static Routing
- Dynamic Routing
- Static routing is done by the administrator manually to forward the data packets in the network. Static routing is permanent. No any administrator can change this setting . These static routers are configured by the administrator, which means there is no need to make routing tables by the router.
- Dynamic Routing is automatically done by the choice of router. It can route the traffic on any route depend on the routing table. Dynamic routing allows the routers to know about the networks and the interesting thing is to add this information in their routing tables. This is shown in the figure 3.1 below. In dynamic routing the routers exchange the routing information if there is some change in the topology . Exchanging information between these dynamic routers learn to know about the new routes and networks. Dynamic routing is more flexible than static routing. In dynamic routing it have the capability to overcome the overload traffic. Dynamic routing uses different paths to forward the data packets. Dynamic routing is better than static routing.
There are several kinds of routing protocols for wireless ad hoc networks. These routing protocols are categorized as reactive or proactive routing protocols . The ad hoc routing protocols which have both proactive and reactive merits, is called hybrid routing protocols. The first kind of protocol is proactive or table driven routing protocol. The second kind of protocol is called reactive or on-demand routing protocol. The first kind of protocol is simply called Proactive MANET Protocol (PMP). Proactive routing protocol detects the layout of the network actively. A routing table can be maintained at every node. From which a route can be determined with less delay. The proactive routing protocols provide good reliability on the current network topology  and low latency for deciding a route. The OLSR is a proactive routing protocol.
The second kind of protocol is simply called Reactive MANET Protocol (RMP). In these kinds of protocols the communication is only possible when the source node requests to communicate with the other node. Reactive MANET Protocols are mostly suited for nodes with high mobility or nodes that transmit data rarely. There are some reactive routing protocols which we will consider here. These reactive routing protocols include AODV, DSR and TORA.
An ad hoc routing protocol is a standard. That controls the decision of the nodes that which route the nodes have to take to the destination from the source node. When a node wants to join a network, it discovers the topology by announcing its presence, and listening to broadcasts from other nodes in the network. This routing discovery is performed differently according to the routing protocol algorithm implemented in the network.
Proactive Routing Protocols
The routing information about all the nodes is build and maintained by the proactive protocols. The proactive routing protocols are independent of whether or not the route is needed . Control messages are transmitted with periodically intervals. Even if there is no data flow still control messages are transmitted. Because of these control messages proactive routing protocols are not bandwidth efficient. There are many advantages and disadvantages of proactive routing protocols. One of its advantages is that the nodes can easily get routing information, and it easily starts a session. The disadvantages are, too much data kept by the nodes for route maintenance, when there is a particular link failure its reform is too slow.
OLSR (Optimized Link State Routing)
It is a proactive routing protocol in MANET. It is also called as table driven protocol because it permanently stores and updates its routing table. OLSR keeps track of routing table in order to provide a route if needed. OLSR can be implemented in any ad hoc network. Due to its nature OLSR is called as proactive routing protocol. MPR nodes are shown in the given figure 3.2. All nodes in the network do not broadcast the route packets. Just Multipoint Relay (MPR) nodes broadcast route packets. These MPR nodes can be selected in the neighbor of source node. Each node in the network keeps a list of MPR nodes. This MPR selector is obtained from HELLO packets sending between in neighbor nodes. These routes are built before any source node intends to send to a specified destination. Each and every node in the network keeps a routing table. This is the reason the routing overhead for OLSR is minimum than other reactive routing protocols and it provide a shortest route to the destination in the network. There is no need to build the new routes, as the existing in use route does not increase enough routing overhead. It reduces the route discovery delay.
Nodes in the network send HELLO messages to their neighbors. These messages are sent at a predetermined interval in OLSR to determine the link status. Here we can understand this by Figure 3.3. If node A and node B are neighbors, node A sends HELLO message to B node. If B node receives this message, we can say the link is asymmetric. If now B node sends the same HELLO message to A node. This is the same as first case, called asymmetric link. Now if the two way communication is possible then we can call it symmetric link, as shown in Figure 3.3. The HELLO messages contain all the neighbor information. This enables the mobile node to have a table in which it has information about all its multiple hop neighbors. A node chooses minimal number of MPR nodes, when symmetric connections are made. It broadcast TC messages with information about link status at predetermined TC interval . TC messages also calculate the routing tables. In TC messages MPR node information are also included.
Reactive Routing Protocols
Reactive routing protocols are called on-demand routing protocols. These routing protocols are called when they are required. So the routes are built when they are needed. These routes can be acquired by sending route requests through the network. Disadvantage of this algorithm is that it offers high latency in searching a network. We will consider AODV and DSR in this report. But the analysis will be of AODV and DSR in the fifth chapter.
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 the destination. The network usage is least. Since the routes are build on demand so the network traffic is minimum. AODV not allowing keeping extra routing which is not in use . Two nodes wish to establish a connection in an ad hoc network. AODV is responsible to enable them to build a multihop route. AODV is loop free. AODV uses Destination Sequence Numbers (DSN) to avoid counting to infinity. 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. One is Route Request (RREQs), Route Replies (RREPs), and Route Errors (RERRs) . By using UDP packets, the sources to destination routes are 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 3.4 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 broadcast 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 3.4 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 it in their routing table. The addresses of the neighbor nodes from which it get the RREQ message. This information will be used to make a reverse path for RREP message from the destination node. When the message reach to the destination node. It calculates the shortest path to the source. In the figure 3.4 it is shown. The destination node B replies with RREP message denoted by the dotted orange color line. From node A to node B the shortest path is the lower one shown with dotted line. These nodes routes information were saved in the routing tables and were used to build a reverse route from destination to the source node with the message RREP. The request reach to the destination and then RREP has 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).
DSR (Dynamic Source Routing)
Dynamic Source Routing Protocol is a reactive routing protocol. DSR is on demand routing protocol. It is a source routing protocol. It is a simple and efficient protocol. It can be used in multi hop wireless ad hoc networks .
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