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Chapter 13

Chapter 13. Ad Hoc Networks (Mobile, Mesh, Sensor). Outline. Introduction Characteristics of MANETs Applications Routing Table-driven Routing Protocols Source-initiated On-demand Routing Hybrid Protocols Vehicular Area Network (VANET) Security Issues in Mobile Ad hoc Networks (MANETs)

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Chapter 13

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  1. Chapter 13 Ad Hoc Networks (Mobile, Mesh, Sensor)

  2. Outline • Introduction • Characteristics of MANETs • Applications • Routing • Table-driven Routing Protocols • Source-initiated On-demand Routing • Hybrid Protocols • Vehicular Area Network (VANET) • Security Issues in Mobile Ad hoc Networks (MANETs) • Network Simulators • Summary

  3. Introduction • Two Basic Types of Wireless Networks:Infrastructure/Peer-to PeerRouter in a wired network, Access Point in a wirelessAd Hoc/Peer-to-Peer (mobile, mesh, sensor) • A Mobile Ad hoc Network (MANET) is an autonomous system of nodes (MSs) (also serving as routers) connected by wireless links • No infrastructure exists in a MANET • The network’s wireless topology may change dynamically in an unpredictable manner since nodes are free to move & each node has limited transmitting power • Information is transmitted in a store-and forward manner (peer-to-peer) using multi hop routing

  4. Introduction (Cont’d) • Each node is equipped with a wireless transmitter and a receiver with an appropriate antenna • We assume that it is not possible to have all nodes within each other’s radio range • When the nodes are close-by i.e., within radio range, there are no routing issues to be addressed • At a given point in time, wireless connectivity in the form of a random multi-hop graph exists between the nodes

  5. MS2 MS4 Asymmetric link MS3 MS5 MS7 Symmetric link MS1 MS6 A Mobile Ad Hoc Network (MANET) MS2

  6. A B Direct Transmission versus Multi-hop A C D E B • Energy ConsumptionGlobal Considerstions Unit Inefficiencies distance is small so a ~ -2 • Time delay

  7. Characteristics of MANETs • Dynamic topologies: Network topology may change dynamically as the nodes are free to move • Bandwidth-constrained, variable capacity links: Realized throughput of wireless communication is less than the radio’s maximum transmission rate Collision occurs frequently • Energy-constrained operation: Some nodes in the ad hoc network may rely on batteries or other exhaustible means for their energy • Limited physical security: More prone to physical security threats than fixed cable networks

  8. Applications • Defense applications: On-the-fly communication set up for soldiers on the ground, fighter planes in the air, etc. (Decentralized command & control) • Crisis-management applications: Natural disasters, where the entire communication infrastructure is in disarray • Tele-medicine: Paramedic assisting a victim at a remote location can access medical records, can get video conference assistance from a surgeon for an emergency intervention • Tele-Geoprocessing applications: Combines geographical information system, GPS and high capacity MS, Queries dependent of location information of the users, and environmental monitoring using sensors • Vehicular Area Network: in providing emergency services and other information in both urban and rural setup • Virtual navigation: A remote database contains geographical representation of streets, buildings, and characteristics of large metropolis and blocks of this data is transmitted in rapid sequence to a vehicle to visualize needed environment ahead of time • Education via the internet: Educational opportunities on Internet to K-12 students and other interested individuals. Possible to have last-mile wireless Internet access

  9. Routing in MANETS - Goals • Provide the maximum possible reliability - use alternative routes if an intermediate node fails • Route network traffic through the path with least cost metric • Give the nodes the best possible response time and throughput Need for Routing • Route computation must be distributed. Centralized routing in a dynamic network is usually very expensive • Routing computation should not involve the maintenance of a global state • Fewer nodes must be involved in route computation • Each node must care about the routes to its destination and must not be involved in frequent topology updates • Stale routes must be either avoided or detected • Broadcasts should be avoided (highly unreliable) • If topology stabilizes, routes must converge to optimal routes • It is desirable to have a backup route when the primary route has become stale

  10. Routing Classification The existing routing protocols can be classified as: • Proactive: when a packet needs to be forwarded, the route is already known • Reactive: Determine a route only when there is data to send Routing protocols may also be categorized as: • Table Driven protocols • Source Initiated (on demand) protocols • Hybrid protocols

  11. Protocol Characteristics

  12. Vehicular Area Network (VANET) • Basic objective is to find some relevant local information, such as close by gas stations, • restaurants, grocery stores, and hospitals, • Primary motivation is to obtain knowledge of local amenities

  13. Vehicular Area Network (VANET) • Hello beacon signals are sent to determine other vehicle in the vicinity • Table is maintained and periodically updated in each vehicle • Vehicle in an urban area move out relatively low speed of up to 56 km/hr while • Speed varies from 56 km/hr to 90 km/hr in a rural region • Freeway-based VANET could be for emergency services such as accident, traffic-jam, traffic detour, public safety, health conditions, etc. • Early VANET used 802.11-based ISM band • 75 MHz has been allocated in 5.850 - 5.925 GHz band • Coverage distance is expected to be less than 30 m and data rates of 500 kbps • FCC has allocated 7 new channels of in 902 - 928 MHz range to cover a distance of up to 1 km using OFDM • It is relatively harder to avoid collision or to minimize interference • slotted ALOHA does not provide good performance • Non-persistent or p-persistent CSMA is adopted

  14. Vehicular Area Network (VANET)

  15. Security Issues in MANETs • Missing authorization facilities hinders the usual practice of distinguishing nodes as trusted or non-trusted • Malicious nodes can advertise non-existent links, provide incorrect link state information, create new routing messages and flood other nodes with routing traffic • Attacks include active interfering, leakage of secret information, eavesdropping, data tampering, impersonation, message replay, message distortion, and denial-of-service (DoS) • Encryption and authentication can only prevent external nodes from disrupting the network traffic • Internal attacks are more severe, since malicious insider nodes are protected with the network’s security mechanism

  16. Disrupting Routing Mechanism by a Malicious Node • Changing the contents of a discovered route • Modifying a route reply message, causing the packet to be dropped as an invalid packet • Invalidating the route cache in other nodes by advertising incorrect paths • Refusing to participate in the route discovery process Routing mechanism attacked by: • Modifying the contents of a data packet or the route via which that data packet is supposed to travel • Behaving normally during the route discovery process but drop data packets causing a loss in throughput • Generate false route error messages whenever a packet is sent from a source to a destination

  17. Attacks by a Malicious Node • Can launch DoS attack • A large number of route requests due to DoS attack or a large number of broken links due to high mobility • Can spoof its IP and send route requests with a fake ID to the same destination • Routing protocols like AODV have many vulnerabilities • Authority of issuing authentication is a problem as a malicious node can leave the network unannounced

  18. Security Approaches • Intrusion Detection System (IDS) • Automated detection • Subsequent generation of an alarm • IDS is a defense mechanism that continuously monitors the network for unusual activity and detects adverse activities • Capable of distinguishing between attacks originating from inside the network and external ones • Intrusion detection decisions are based on collected audit data • Intrusion Response Mechanism (IRM) • Depends on the type of intrusion • Likely responses include: reinitializing communication channels between nodes, identifying the compromised nodes, and staring a re-authentication process among all nodes

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