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[MOBILE AD-HOC NETWORK (MANET)]

2015DR. B.C ROY ENGINEERING COLLEGE DURGAPUR

MONODIP SINGHA ROY M.TECH (ECE) 1st YEAR REG NO:151200410028

MOBILE AD-HOC NETWORKS

ABSTRACT

AD-hoc network (called as computer-to computer network) is a temporary network used to share for presentation, sharing files and even internet among computer and other devices. An ad-hoc network is a local area network (LAN) that is built spontaneously as devices connect. Instead of relying on a base station to coordinate the flow of messages to each node in the network, the individual network nodes forward packets to and from each other. In Latin, ad hoc literally means "for this," meaning "for this special purpose" and also, by extension, improvised .The use of mobile ad hoc networks (MANETs) has been widespread in many applications, including some mission critical applications, and as such security has become one of the major concerns in MANETs. Due to some unique characteristics of MANETs, prevention methods alone are not sufficient to make them secure; therefore, detection should be added as another defense before an attacker can breach the system. In general, the intrusion detection techniques for traditional wireless networks are not well suited for MANETs.

INTRODUCTION

Ad-hoc networking is often justified by scenarios where you do not want or where you cannot deploy & manage an infrastructure. Spontaneous meetings (at work, airport): exchange files, play games. Special circumstances: disaster relief. Or simply cabeling costs, management overhead: old building, “wearable LAN”, wireless headset.

In the next generation of wireless communication systems, there will be a need for the rapid deployment of independent mobile users. Significant examples include establishing survivable, efficient, dynamic communication for emergency/rescue operations, disaster relief efforts, and military networks. Such

2 | P a g e M A N E T

network scenarios cannot rely on centralized and organized connectivity, and can be conceived as applications of Mobile Ad Hoc Networks. The set of applications for MANETs is diverse, ranging from small, static networks that are constrained by power sources, to large-scale, mobile, highly dynamic networks. The design of network protocols for these networks is a complex issue. Regardless of the application, MANETs need efficient distributed algorithms to determine network organization, link scheduling, and routing. However, determining viable routing paths and delivering messages in a decentralized environment where network topology fluctuates is not a well-defined problem. While the shortest path (based on a given cost function) from a source to a destination in a static network is usually the optimal route, this idea is not easily extended to MANETs. Factors such as variable wireless link quality, propagation path loss, fading, multiuser interference, power expended, and topological changes, become relevant issues. The network should be able to adaptively alter the routing paths to alleviate any of these effects. Moreover, in a military environment, preservation of security, latency, reliability, intentional jamming, and recovery from failure are significant concerns. Military networks are designed to maintain a low probability of intercept and/or a low probability of detection. Hence, nodes prefer to radiate as little power as necessary and transmit as infrequently as possible, thus decreasing the probability of detection or interception. A lapse in any of these requirements may degrade the performance and dependability of the network.

BACKGROUND

A mobile ad hoc network (MANET) is a continuously self-configuring, infrastructure-less network of mobile devices connected without wires.

Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router. The primary challenge in building a MANET is equipping each device to continuously maintain the information required to properly route traffic. Such networks may operate by themselves or may be connected to the larger Internet. They may contain one or multiple and different transceivers between nodes. This results in a highly dynamic, autonomous topology.

MANETs are a kind of Wireless ad hoc network that usually has a routable networking environment on top of a Link Layer ad hoc network.


MANETs consist of a peer-to-peer, self-forming, self-healing network. MANETs circa 2000-2015 typically communicate at radio frequencies (30 MHz - 5 GHz).

The growth of laptops and 802.11/Wi-Fi wireless networking has made MANETs a popular research topic since the mid-1990s. Many academic papers evaluate protocols and their abilities, assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other. Different protocols are then evaluated based on measures such as the packet drop rate, the overhead introduced by the routing protocol, end-to-end packet delays, network throughput, ability to scale, etc.

Fig: Ad-Hoc Wireless

[1] Types of MANET

There are different types of MANETs including:

InVANETs – Intelligent vehicular ad hoc networks make use of artificial intelligence to tackle unexpected situations like vehicle collision and accidents.

Vehicular ad hoc networks (VANETs) – Enables effective communication with another vehicle or helps to communicate with roadside equipments.

Internet Based Mobile Ad hoc Networks (iMANET) – helps to link fixed as well as mobile nodes.


[2] Characteristics of MANET

In MANET, each node acts as both host and router. That is it is autonomous in behavior.

Multi-hop radio relaying- When a source node and destination node for a message is out of the radio range, the MANETs are capable of multi-hop routing.

Distributed nature of operation for security, routing and host configuration. A centralized firewall is absent here.

The nodes can join or leave the network anytime, making the network topology dynamic in nature.

Mobile nodes are characterized with less memory, power and light weight features.

The reliability, efficiency, stability and capacity of wireless links are often inferior when compared with wired links. This shows the fluctuating link bandwidth of wireless links.

Mobile and spontaneous behavior which demands minimum human intervention to configure the network.

All nodes have identical features with similar responsibilities and capabilities and hence it forms a completely symmetric environment.

High user density and large level of user mobility. Nodal connectivity is intermittent.

[3] MANET Challenges

Manet environment has to overcome certain issues of limitation and inefficiency. It includes:

The wireless link characteristics are time-varying in nature: There are transmission impediments like fading, path loss, blockage and interference that add to the susceptible behavior of wireless channels. The reliability of wireless transmission is resisted by different factors.

Limited range of wireless transmission – The limited radio band results in reduced data rates compared to the wireless networks. Hence optimal usage of bandwidth is necessary by keeping low overhead as possible.

Packet losses due to errors in transmission – MANETs experience higher packet loss due to factors such as hidden terminals that results in collisions, wireless channel issues (high bit error rate (BER)), interference, and frequent breakage in


paths caused by mobility of nodes, increased collisions due to the presence of hidden terminals and uni-directional links.

Route changes due to mobility- The dynamic nature of network topology results in frequent path breaks.

Frequent network partitions- The random movement of nodes often leads to partition of the network. This mostly affects the intermediate nodes.

[4] MANET Security

The aims of Ad hoc networks and particularly MANET have in recent years not only seen widespread use in commercial and domestic application areas but have also become the focus of intensive research. Applications of MANET’s range from simple wireless home and office networking to sensor networks and similarly constrained tactical network environments. Security aspects play an important role in almost all of these application scenarios given the vulnerabilities inherent in wireless ad hoc networking from the very fact that radio communication takes place (e.g. in tactical applications) to routing, man-in-the-middle and elaborate data injection attacks.

Protecting Mobile ad-hoc network, an ad hoc routing protocol is a convention, or standard, that controls how nodes decide which way to route packets between computing devices in a mobile ad-hoc network. In ad hoc networks, nodes do not start out familiar with the topology of their networks; instead, they have to discover it. The basic idea is that a new node may announce its presence and should listen for announcements broadcast by its neighbors. Each node learns about nodes nearby and how to reach them, and may announce that it, too, can reach them. Note that in a wider sense, ad-hoc protocol can also be used literally, that is, to mean an improvised and often impromptu protocol established for a specific purpose.

I) Reactive Approach:

Seeks to detect security threats and react accordingly. This type of protocols maintains fresh lists of destinations and their routes by periodically distributing


routing tables throughout the network. The main disadvantages of such algorithms are:

1. Respective amount of data for maintenance.

2. Slow reaction on restructuring and failures.

There are two main things in re-active routing protocols first is that it never take initiative in order to take routes for network, second is that whenever it creates routes it will developed on demand by flooding mechanism. In such kind of routing protocols there are some advantages and disadvantages which are given below:

Whenever they need to find out the routes they use bandwidth otherwise it will not use bandwidth.

There is lot of overhead because of the flooding process. At start there is delay in the network.

There are three steps which will explain the complete procedure of the re-active routing protocols:

1. If there are two nodes at position A and position B which want to communicate.

2. In order to communicate with the B, A needs to flood the routes towards the B.

3. In order to create communication between A and B unicast feedback will come back.

II) Proactive Approach:

Attempts to prevent an attacker from launching attacks through various cryptographic techniques: This type of protocols maintains fresh lists of destinations and their routes by periodically distributing routing tables throughout the network. The main disadvantages of such algorithms are:

1. Respective amount of data for maintenance.


2. Slow reaction on restructuring and failures.

In pro-active routing protocols the mechanism is different than the re-active routing protocols. In this category of protocols basically routes are depends upon the traffic control which is continuous. All routing information maintained at any time of the network because we know that network is dynamic which changes its size by making its size increasing or decreasing. There are also some advantages and disadvantages in this type of protocols which we will discuss here. Basically there are two main things which are keep in mind first one is that due to the continuous control traffic mechanism there is lot of overhead on the network which is one of the drawback of the pro-active routing protocols. One good thing among the pro-active routing protocols is that all the time routes are available, due to this way there is an ease of communication among the nodes or devices

[5] MANET Usage Areas

Military Scenario Sensor Usage Rescue Operation Student on Campus Free internet connection sharing Conferences

[6] PROS and CONS

PROS:

Separation from central network administration. Self-configuring nodes are also routers. Self-healing through continuous re-configuration. Scalability incorporates the addition of more nodes. Mobility allows ad hoc networks created on the fly in.


CONS:

Limited resources and physical security. Intrinsic mutual trust vulnerable to attacks. Lack of authorization facilities. Volatile network topology makes it hard to detect malicious

nodes. Security protocols for wired networks cannot work for ad hoc

networks.

[7] CONCLUSION

A Mobile Ad-Hoc Network (MANET) is an autonomous collection of mobile users that communicate over relatively bandwidth constrained wireless links. Since the nodes are mobile, the network topology may change rapidly and unpredictably over time. The network is decentralized, where all network activity including discovering the topology and delivering messages must be executed by the nodes themselves, i.e., routing functionality will be incorporated into mobile nodes.

MANETs are a new technology increasingly used in many applications. These networks are more vulnerable to attacks than wired networks. Since they have different characteristics, conventional security techniques are not directly applicable to them. Researchers currently focus on developing new prevention, detection and response mechanism for MANETs.


[8] REFERENCES

[1]. D. Johnson and D. Maltz, “Dynamic Source Routing in Ad Hoc Wireless Networks,” Mobile Computing, T. Imielinski and H. Korth, Ed., Kluwer, 1996. [2]. C. Perkins and E Royer, “Ad Hoc On-Demand Distance Vector Routing,” 2nd IEEE Workshop. Mobile Comp. Sys. And Apps, 1999. [3]. IEEE Std. 802.11, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” 1997.[4]. Sridhar Iyer, “Mobile Ad-Hoc Networks”, IIT Bombay.[5]. Andreas Tønnesen, “Introduction to MANET”.[6]. “Wireless Ad-Hoc Network” – Wikipedia.[7]. Md. Mahbubul Alam, And Tanmoon Taz Shetu, “Congestion control in Mobile Ad-Hoc Networks (MANETs)”, APRIL 2011.


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