Extending MANET Routing Protocol by Adding

Extending MANET Routing Protocol by adding

Gateway Mode

1Asish P Mathew, 2 Lakshmi K S

Rajagiri School of engineering and technology, kakkanad, kochi

Abstract— A Mobile Ad-Hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without using any centralized access point, infrastructure, or centralized administration. Routing protocols for ad hoc wireless networks can be classified into several types based on route discovery, data delivery and route maintains. In this paper, try to improve the performance of an already existing routing protocol named AODV [Ad hoc On-Demand Distance-Vector Routing Protocol] by modifying its basic structure.

In this work, proposed a new variant of AODV routing protocol that is a combination of AODV+ and R-AODV. The proposed protocol, R-AODV [M], simulated with NS-2 (version 2.34) and we compared the performance indicator in hybrid ad hoc network scenario. The experiment result shows that our modified protocol outstanding in many situations. This paper mainly focuses on why I select AODV for my research? What performances are improved?

Index Terms— Mobile Ad Hoc Networks (MANETs), routing misbehavior, Ad hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR), Destination- Sequenced Distance Vector (DSDV) ,Gateways, Reverse AODV (RAODV)

I. INTRODUCTION

Mobile ad-hoc network [MANET] is widely popular at beginning of 20-th century for data monitoring and mining. Depends on the area of working MANET are mainly classified into Vehicular Ad hoc Networks (VANETs), Internet based mobile ad hoc networks (iMANET) and Intelligent vehicular ad hoc networks (InVANETs). An ad hoc network is collection of nodes that do not need a fixed infrastructure. This type of network formed and partitioned dynamically and they don’t have any centralized monitor facility. The nodes are mobile, so it uses air as the medium of connectivity. For example, in a conference room ad hoc network formed between employees Laptops or workstations. Usually the performance of nodes in ad hoc network is crucial in many cases like available memory,

power, bandwidth and many other factors. The networks usually not used for fixed data transmission.

The primary challenge of design a MANET is maintain device to properly route traffic. Such network may standalone or incorporated with Internet. The growth of mobile and Laptops make MANET as a popular research topic. In this paper is mainly focus on the following points:

1. Study the working of varies MANET routing protocols.

2. Performance Comparison of DSDV, DSR, AODV

routing protocol.

3. AODV reactive routing protocol is expanding to support communication between the MANET and the Internet.

4. Propose a new variant of AODV routing Protocol, called R-AODV[m].

5. Simulation using ns2 to determine the performance of modified protocol.

II. STUDY THE WORKING OF VARIES MANET ROUTING PROTOCOLS

There are several ways to study MANETs. One solution is based on various routing protocols like AODV, DSR and DSDV. These protocols often used as the base of other protocols shall be evaluated. The common working ideas of all these protocols are similar except connection establishment, Packet delivery and route updating and maintains. Fig 1 depicts a simple classification of different routing protocols. The characteristics of each are described in following sections.

A. DSDV

Destination-Sequenced Distance Vector [DSDV] is a proactive, hop-by hop distance vector protocol which use Bellman-Ford algorithm. In which each node maintain a routing table listing next hop and distance to each neighboring nodes. The entries in the list change dynamically so it requires periodic advertisement for its routing table update. In addition, when the network encounters any major change the advertisement happens. This periodic update makes some unnecessary traffic flows and disturbing the mobile nodes if they are in sleep mode. In this way nodes exchange information if destination is long range.

B. DSR

Fig 1. Routing Protocols

RREQ messages. To avoid traffic overflow each host keep Host id, Broadcast id couple. That means each host keep record of RREQ message its forward. Route maintains phase use RRER messages for indicating broken paths. To avoid RREP looping and freshness of the route, destination sequence number is used. The sequence number is monotonically increased based on the route maintains phase. The larger sequence number indicate fresher route. The sequence number of the RREP message always greater than or equal to corresponding RREP message to avoid source to adopt older path. When initiator receives more than one RREP, select the message with larger sequence number. Suppose initiator receives more than one path [RREP] with same sequence number, select path with shortest distance. AODV have some added advantage over other protocols, its low byte order and loop free routing using the destination sequence number are important features.

The Dynamic Source Routing [DSR] is an on-demand routing protocol based on source routing. The nodes are communicated when it requires data exchange. Route discovery and maintains based on dynamic change in topology. Usually DSR keeps multiple routes to destination this may help easy load balancing and fault tolerance. Suppose a node wants to communicate with any other node. First it looks on its route cache. If it found a valid route, the sender uses this route for data propagation. Otherwise it initiate route discovery phase.

The routing protocol is combination of Route Discovery and Route Maintenance. In DSR, the sender does not found a valid route in its cache. The sender broadcast a ROUTE REQUEST, by specifying destination and unique source id. Each node receiving the REQUEST appends its own address and rebroadcast the REQUEST. When the REQUEST reaches its target, it sends positive ROUTE REPLY back to the initiator through the REQUEST flows including accumulated list of path address. Initiator updates the route cache and forwards the data. DSR have Route Maintenances mechanism by means of passive acknowledgement. If limited number of node unable to send a packet, it returns ROUTE ERROR to the original source of the packet. The sender removes broken link from its route cache initiate a fresh Route discovery procedure.

C. AODV

Ad Hoc On-Demand Distance Vector [AODV] is reactive routing protocol. The main advantage of this protocol each node does not keep entire topology and avoid periodic update. The mobile nodes generate traffic only when it needs to discover or maintain a route. The expiration time is used for dynamic route maintains.

AODV protocol is purely on demand and based distance vector technology. Each host only knows how to reach its neighbors. When source wants to send something, it will broadcast ROUTE REQUEST [RREQ]. Whenever destination gets an route request it immediately generate a ROUTE REPLY [RREP] and unicast back to the source. If a RREP packet is send, the packet will append the route to the destination through this packet. So there exists more than on path to destination, a mobile host may receive more than one

III. PERFORMANCE COMPARISON OF DSDV, DSR AND AODV ROUTING PROTOCOLS

This section emphasis simulating the performance of varying ad hoc routing protocols DSDV, DSR, AODV with varying number of mobile nodes. For wireless simulation, numbers of open source software available in the market NS2, NetSim, OPNET are some of them. Here choose NS2 for performance comparison.

The NS2 is discrete event simulation software, it simulates events such as sending, receiving, forwarding and dropping packets. The latest version NS-allinone-2.34 supports almost all popular routing protocols such as DSDV, DSR and AODV. NS-2 use Object Tool Command Language [OTCL] as its front end and C++ for its backend compilation. The performance metrics are graphically visualized in XGRAPH [Fig 3, 4, 5, 6, and 7]. NS-2 also offers visual representation of topology and node movement in a Network Animator [NAM]. Fig 2 shows data-flow of simulation environment.

Fig 2. Simulation Model

Network of nodes placed in 1000m X 800m block area. The performance of DSDV, DSR, AODV are evaluated by keeping network speed and pause time constant and varying the network size [number of mobile nodes]. Table 1. Shows the simulation parameter used in this valuation.

Table 1. Parameter values for Simulation

The simulation results are shown in following subsection in the form of line charts. While analyzing these protocols with chain topology and focus on following performance metric such as:

1. Generated Packets vs. Number of nodes

2. Received Packets Vs. numbers of nodes

3. Total Dropped Packets Vs. numbers of nodes.

4. Packet Delivery Ratio Vs. numbers of nodes

5. Average End to End delay Vs. numbers of nodes

Fig 3. Generated Packets

Fig 4. Received Packets Vs. numbers of nodes

Fig 5. Total Dropped Packets Vs. numbers of nodes.

Fig 6. Packet Delivery Ratio Vs. numbers of nodes

Fig 7. Average End to End delay Vs. numbers of nodes

Simulation results are listed in Table 2. Wherefrom the best performing protocol is select for optimize MANET performance. In slow speed mobile nodes, Packet sent and received difference in AODV is more than DSR with scenario mobile nodes moving at 5ms [2].In high speed mobile nodes, Packet sent and received difference in AODV is more than DSR with scenario mobile nodes moving at 10ms [2].In very high speed mobile nodes, Packet sent and received difference

in AODV is more than DSR with scenario mobile nodes moving at 15ms [2].Considering small number of hops, Packet sent and received difference in DSR is less than AODV, but total packet sent amount is very high in AODV than DSR. As AODV is sent 2409 TCP packets where as in DSR sent only

20 TCP packets in 150 sec and hence TCP packet lost rate is also less in DSR and which is inefficient than AODV as it is able to send only few packets during time interval. Considering large number of hops, Packet sent and received difference in DSR is less than AODV, but total packet sent amount is very high in AODV than DSR. As AODV is sent

1342 TCP packets where as in DSR sent only 18 TCP packets in 150 sec and hence TCP packet lost rate is also less in DSR and which is inefficient than AODV as it is able to send only few packets during time interval [2].

Table 2. Best Performing Protocol

IV. AODV REACTIVE ROUTING PROTOCOL IS EXTENDED TO SUPPORT COMMUNICATION BETWEEN MANET AND INTERNET

Simulation result shows that DSR and AODV are equally best in ad hoc routing field. Further research, I need to concentrate one of the above protocols. In this paper mainly focus on AODV because network with high traffic and mobility the performance of this protocol is stable. There exist many variations of AODV, for example One of AODV variant that has been successful overcoming the disadvantages of basic AODV is R-AODV (Reverse-AODV).Most of the situation the sensor network is purely ad hoc. However, occasionally some situations nodes in MANET need to access Internet. We need some special purpose gateways [Base station] to connect MANET to infrastructure networks. Although some papers discussed about MANET routing protocol in hybrid network, it is a challenging task to increase AODV performance in that kind of network. In this paper, gateway module is implemented in R-AODV routing protocol, so mobile nodes could access Internet through a node that act as the gateway. We called our protocol is R-AODV[m].

In hybrid ad hoc network gateway can act as the communicating agent between MANET and public internet. For MANET nodes wishes to communicate with wired node in outside domain, it needs global internet connectivity through base-station nodes. Any MANET node may act as gateways but in order to ensuring the reliability and throughput of the network usually follows some well-defined criteria’s. Consider any hybrid ad-hoc domain there may one or more gateways are provisioned. In this paper, we examine performance of AODV+, R-AODV and R-AODV[m]. The reason we considering these protocols are they may support gateway mode in hybrid ad-hoc network. Fig 8 shows a simple hybrid ad-hoc network scenario. Here, we extend wireless simple wireless topology to create a mixed scenario consisting of wired and wireless nodes.

Fig 8. Hybrid Network

A. AODV+

In AODV+, a gateway module is added to work in hybrid environment. The nodes in this scenario can be connected each other and with nodes in infrastructure network through specialized base-station nodes.

Gateway Operation: When a gateway receive valid RREQ message. These protocol checks, if there may other valid route in its local cache. If the address is not found, the gateway immediately sends a RREP message with an I flag [RREP-I] back to the initiator of RREQ. Suppose the gateway found a valid route it forward the RREP message normal in addition of it optionally send a RREP-I back to initiator of RREQ. This mechanism will generate a default route for increasing reliability. Gateway keeps this route limited period of time; this may help mobile nodes for future internet access. There are three methods to discover gateway node in the network. In reactive method, mobile node initiates the gateway selection procedure. In proactive method, gateway discovery procedure is automatically executed by already existing gateway in periodic manner. There is another method named hybrid approach, it’s a combination of above two.

B. R-AODV

The extended AODV called Reverse-AODV [R-AODV]. In on-demand routing protocol losing a RREP of AODV protocol make series impact on entire routing procedure. RREP loss leads to source needs to reinitiate the route discovery process which cause increase the traffic congestion, leads to more power consumption, reduce throughput and increase end-to- end delay. The main aim of R-AODV is to avoid RREP loss and improve the performance of AODV. R-AODV follows the same procedure for route discovery. But route reply it use special manner. We call route replay message Reverse-request [R-RREQ]. R-AODV protocol can reply from destination to source if there is at least one path to source node. In this manner, R-AODV prevents a large number of retransmissions of route request messages, and hence diminishes the congestion in the network. Moreover, R-AODV will improve the routing performance such as packet delivery ratio and end- to-end delay.