Be exposed to Ad-Hoc networks

1. Unit – IV
AD-HOC NETWORKS

2. • Ad-Hoc Basic Concepts - Characteristics -
Applications - Design Issues - Routing -
Essential of Traditional Routing Protocols -
Routing Protocols - Vehicular Ad Hoc networks
(VANET) - MANET Vs VANET - Security.

3. B
A
C
D
E
Switching Center
+
Gateway
Path from C to E
Base Station Mobile Node
Figure A cellularnetworks.
53

4. B
A
C
F
D
E
Path from C to E
Mobile Node Wireless Link
Figure. An ad hoc wireless networks
64

5. Differences between cellular networks and ad hoc wireless
networks
Cellular Networks Ad Hoc Wireless Networks
Fixed infrastructure-based Infrastructure-less
Single-hop wireless links Multi-hop wireless links
Guaranteed
bandwidth (designed
for voice traffic)
Shared radio channel
(more suitable for best-effort data traffic)
Centralized routing Distributed routing
Circuit-switched
(evolving toward packet switching)
Packet-switched
(evolving toward emulation of
circuit switching)
Seamless connectivity
(low call drops during handoffs)
Frequency path
break due to
mobility
High cost and time of deployment Quick and cost-effective deployment
Reuse of frequency spectrum
through geographical channel
reuse
Dynamic frequency reuse based on
carrier sense mechanism
7
5

6. Differences between cellular networks and ad hoc
wireless networks (cont.)
Easier to achieve time synchronization Time synchronization is difficult
and consumes bandwidth
Easier to employ bandwidth reservation Bandwidth reservation requires
complex medium access control
protocols
Application domains include mainly
civilian and commercial sector
Application domains include battlefields,
emergency search and rescue operation,
and collaborative computing
High cost of network
maintenance (backup power
source, staffing, etc.)
Self-organization and maintenance
properties are built into the network
Mobile hosts are of relatively low complexity Mobile hosts require more intelligence
(should have a transceiver as well
as routing/switching capacity)
Major goals of routing and call admission
are to maximize the call acceptance ratio
and minimize the call drop ratio
Man aim of routing is to find paths
with minimum overhead and also
quick reconfiguration of broken
paths
Widely deployed and currently in the
third generation
Several issues are to be addressed for
successful commercial deployment
even though widespread use exists in
defense
8
6

19. characteristics of adhoc network
• Lack of fixed Infrastructure
– Nodes can communicate
• Directly within the transmission range
• Through multi-hop communication
• Dynamic topology
– Network topology changes unpredictably
– Rate of topology change
• Movement speed of the mobile devices

20. – Vary with time and MANET application
• Bandwidth constrained, variable capacity links
– Have low bandwidth capacity
– Factors that affects Bandwidth
• Fading
• Noise
• Interference
• Energy Constrained operation
– Small battery
• Store very limited amounts of energy
– Transmissions and Processing during routing
consumes energy

21. • Increased Vulnerability
– Prone to new types of security threads
– Security Threads
• Eavesdropping
• Spoofing
• Denial-of-service (DoS)
– Difficult to identify the attacker
• Device keep moving
• Do not have a global identifier
– Nodes are vulnerable to capture and compromise

22. Applications
• Communication among portable computers
– Portability should be within the range of wireless
hub
• Reduce device flexibility and mobility
• Example
– Cell phone
– Laptop
– Ear phone
– Wrist watch
• Group of people in a conference can share data

23. • Environmental Monitoring
– Collection of various types of data about the
environment in which it is deployed
– Applications
• Environmental Management
• Security Monitoring
• Road Traffic Monitoring
• Road Traffic Management
– Continuous data collection from remote locations
– Miniature Sensors
• Effective means of gathering environmental
information
– Rainfall
– Humidity
– Presence of animal, etc.,

24. – Environmental Monitoring Application
• Deploys large number of sensors nodes in environment
• Deploys adhoc sensor networks to collect data from remote locations
• Sensor nodes respond with commands issued by data collection
centre
• MANETs efficiently handle
• Military
– Set up an adhoc network in a frontline battle field with various
military equipment
• Take advantage of an information network among
– Soldiers
– Vehicles
– Military Information Headquarters
• Emergency Applications
– Adhoc networks can be easily and rapidly deployed
• Search and rescue operation after a natural disaster
• Policing and Fire fighting
• crowd control

25. Design Issues
• Network size and node density
• Network Size
– Refers to the geographic coverage area of the network
• Node Density
– Refers to the number of nodes per unit geographical area
• Clustering required for large networks to avoid network overhead
– Depends on node density
• Connectivity
• Refers to number of neighboring nodes with in transmission range
• Link between two nodes
• Link capacity refers bandwidth of the link
• In MANET
– Number of neighboring bodes
– Capacities of Links
» Vary significantly
• Network topology
• Refers connectivity among various nodes of the network
• Factors that affect the topology
– Mobility of nodes
– Hardware failures
– Discharged batteries
• Issues
– Rate at which the topology changes

26. • User traffic
• Design based on
– Node density
– Average rate of node movements
– Expected traffic
• Common traffic types
– Bursty traffic
– Large packets send periodically
– Combination of above two
• Operational environment
• Environment is either
– Urban
– Rural
– Maritime
• Supports Line of Sight (LoS) communication
• Requires different design of mobile networks due to difference in
– Node density
– Mobility Values

27. • Energy constraint
• Energy required for store and forward packets
– In MANETS, mobile nodes store and forward packets
» Nodes act as routers
• Routing consumes extra battery power

28. ROUTING IN MANET
• Purpose
– To find a path between source and destination
and to forward the packets appropriately
• Example
– Each node must be able to forward data for other
nodes
– Consider the following ad-hoc network

29. – a certain time t1
• Network topology will be shown as below

30. • In MANETs, routing is more expensive and
difficult due to
– Use minimum of available resources (such as
battery power) to find routes
– Nodes have to find route by themselves every
time before transmitting the packets

31. • Functions of each node in MANET
• Forward the packet to the next hop
• Before forwarding, Sender has to ensure that:
– the packet moves towards its destination
– the number of hops(path length) to destination is
minimum
– Delay is minimized
– Packet loss is mimimum through the path
– Path does not have a loop

32. Routing Challenges in MANET
• Host is no longer an end system - can also be an
acting intermediate system
• Changing the network topology over time
• Potentially frequent network partitions
• Every node can be mobile
• Limited power capacity
• Limited wireless bandwidth
• No centralized entity –distributed
• Presence of varying channel quality

33. ESSENTIALS OF TRADITIONAL
ROUTING PROTOCOLS
• Types
– Link state routing
– Distance vector routing
• Popular in packet-switched networks
• Finds the shortest path to the destination based on
number of hops in the route

34. LINK STATE PROTOCOLS (LSP)
• Link state denotes connection establishment of
one router with another router
• a neighboring node of a router will directly
communicate without any intermediate routers
• Also known as shortest path first algorithms
• Each routers learns about its own directly
connected networks
• Each node maintains a network topology based
on cost for each link

35. • Each router determines its local connectivity
information and floods to other nodes in the
network through link state advertisement
• Each router in the network stores the information
present in the link state advertisement in link
state packet database (LSPDB)
• All routers in network maintains
– LSPDB and
– Routing table
• Each routers in the network have identical LSPDB

36. Routing Process
• Router floods the Link state advertisement to all
of its neighbors
• A router receives this Link state advertisement
examines the sequence number and keeps the
most recent one by consulting its LSPDB
• The router forwards a copy to its neighbor
• Using Link state advertisement stored in LSPDB a
router constructs a tree using Dijikstra’s algorithm
• Using this algorithm a shortest path tree is
constructed edge by edge

37. Link State tree Construction
• Each router maintains two data structure
– A shortest path tree containing nodes
– List of candidates
• Initially this algorithm starts with both the data structures as empty
• It first adds itself as a route of the tree and add other neighboring
routers as nodes
• All routers are connected by emptying the candidate list
• The above step is repeated until candidate list is empty
• Once a network topology is formed a router uses its routing table to
find the shortest path to the destination
• Rooting loops are formed when two nodes sends packet to each
other endlessly
• Link state protocols are:
– Open Shortest Path First (OSPF)
• Intermediate System to Intermediate System (IS-IS)

38. DISTANCE VECTOR (DV) ROUTING
PROTOCOL
• Each node knows the distance (=cost) to its directly connected neighbors
• Routing decisions are based on number of hops the packet have to
traverse to reach the destination
• Here vector denotes distance and direction, that is number of hops to the
destination and the next hop to the router
• Also known as Distributed Bellman-Ford or RIP (Routing Information
Protocol)
• each router broadcast the routing information to all of its neighbors
• A node sends periodically a list of routing updates to its neighbors
• All the neighboring nodes updates its own routing table based on the
routers broadcasted information
• Routers does not know entire path to the destination. Instead they have:
– Direction in which packets have to be forwarded
– its own distance from destination
• popular routing protocols based on distance vector are
– Routing Information Protocol(RIP)
– Interior Gateway Routing Protocol (IGRP)

39. MANETS VS TRADITIONAL ROUTING
MANETs Routing Traditional Networks
Each node acts as a router Nodes do not participate in packet routing
Topology is dynamic Topology is static
IP-based addressing scheme does not work Simple IP-based addressing scheme is deployed

41. PROACTIVE (TABLE-DRIVEN)
PROTOCOLS
• Also known as table-driven routing protocols
• Each node in the routing table maintains information about routes to
every other node in the network
– Tables are updates frequently due to
• Changes in network topology
– Node Movements
– Nodes shutting down
– Nodes can determine the best route to a destination
• Generates a large number of control messages to keep the routing tables
up-to-date
– Generates overhead which consumes large part of available bandwidth
• Drawback
– Does not suitable for large networks
• Size of routing table is large
• Example
– Destination Sequenced Distance Vector (DSDV) protocol

42. DESTINATION SEQUENCED DISTANCE-
VECTOR (DSDV)
• It is a table-driven (Pro-active) routing protocol
• Based on classical distributed Bellman-Ford routing
mechanism
• Routing loop is avoided by using number sequencing
• Each mobile node maintains a routing table in terms of
number of hops to each destination.
• Routing table updates are periodically transmitted
• Each entry in the table is marked by a sequence number
which helps to distinguish stale routes from new ones, and
thereby avoiding loops.
• Updated routing tables are exchanged periodically to
maintain table consistency

43. • Important steps in operation of DSDV
• Each router collects information from all its neighbor
• The node determines the shortest path to the
destination
• A new routing table is generated
• The router broadcasts the generated table to its
neighbors
• The neighboring nodes reconstructs their own routing
table
• This process continues till information becomes stable
in the network

44. • Routing table updates in DSDV are distributed by
two different types of update packets:
• Full dump: This type of update packet contains all
the routing information available at a node. As a
consequence, it may require several Network
Protocol Data Units (NPDUs) to be transferred if
the routing table is large. Full dump packets are
transmitted infrequently if the node only
experiences occasional movement.
• Incremental: This type of update packet contains
only the information that has changed since the
latest full dump was sent out by the node. Hence,
incremental packets only consume a fraction of
the network resources compared to a full dump.

46. Advantages
• DSDV was one of the early algorithms
available. It is quite suitable for creating ad
hoc networks with small number of nodes.
Since no formal specification of this algorithm
is present there is no commercial
implementation of this algorithm.
• DSDV guarantees for loop free path.

47. Disadvantages
• DSDV requires a regular update of its routing
tables, which uses up battery power and
a small amount of bandwidth even when the
network is idle.
• Whenever the topology of the network
changes, a new sequence number is necessary
before the network re-converges; thus, DSDV
is not suitable for highly dynamic networks.

48. REACTIVE (ON-DEMAND) PROTOCOLS
• Also called as On-demand routing protocol
• Nodes do not maintain up-to-date routing
information
– New routes are discovered only when required
• Uses flooding technique to determine the route
– Flooding technique is used when the node does not
have routing knowledge
• Advantages
– Reduce large overheads

49. – Eliminate periodic updates
– Adaptive to network dynamics
• Disadvantages
– High flood-search overhead
– Mobility, distributed traffic
– High route acquisition latency
• Example
– Dynamic Source Routing (DSR)
– Adhoc on-demand distance vector routing (AODV)

50. DYNAMIC SOURCE ROUTING (DSR)
• Developed for MANETs with small diameter and less mobility
• It is a source initiated On-demand (reactive) routing protocol
• Uses source routing, the sender determines the complete sequence
of the node to travel
• Exchanges routing table periodically
• Each node maintains a route cache which contains list of all nodes
• When a node finds a new route it adds in its cache
• Also maintains sequence counter to identify last request generated
• The protocol consists of two major phases: Route Discovery, Route
Maintenance

51. Route Discovery
• When a mobile node has a packet to send to some
destination, it first consults its route cache to check
whether it has a route to that destination.
• If it is an un-expired route, it will use this route.
• If the node does not have a route, it initiates route
discovery by broadcasting a Route Request packet.
• This Route Request contains the address of the
destination, along with the source address.
• Each node receiving the packet checks to see whether
it has a route to the destination. If it does not, it adds
its own address to the route record of the packet and
forwards it.

52. • Route Reply message containing path information is
sent back to the source either by
– the destination, or
– intermediate nodes that have a route to the destination
– Reverse the order of the route record, and include it in
Route Reply.
– Unicast, source routing
• If the node generating the route reply is the
destination, it places the route record contained in the
route request into the route reply.
• Each node maintains a Route Cache which records
routes it has learned and overheard over time

64. AD HOC ON-DEMAND DISTANCE
VECTOR (AODV)
• AODV = Ad Hoc On-demand Distance Vector
• Routing protocol designed for wireless and
mobile ad hoc networks
• AODV is an improvement over DSDV, which
minimizes the number of required broadcasts by
creating routes on demand.
• Route discovery and route maintenance are same
as DSR
• Uses hop-by-hop routing, Sequence numbers and
beacons

65. • A source node initiates a path discovery
process broadcasts a Route Request (RREQ)
packet to its neighbors.
• Source floods route request in the network.
• Reverse paths are formed when a node hears
a route request.
• Each node forwards the request only once
(pure flooding).
• Route reply forwarded via the reverse path.

67. ZONE ROUTING PROTOCOL (ZRP)

75. VEHICULAR ADHOC NETWORKS
(VANETs)
• A Vehicular Ad-hoc Network (VANET) is a type of
Mobile Ad-hoc Network (MANET) that is used to
provide communications between nearby
vehicles, and between vehicles and fixed
infrastructure on the roadside.
• Vehicular communication in VANETs can be
achieved by exchanging information using
Vehicle-to-Vehicle (V2V) and Vehicle-to-
Infrastructure (V2I) communications to
provide road safety, navigation, and other
roadside services.

76. Introduction
How vehicular communications work
- road-side infrastructure units (RSUs),
named network nodes, are equipped
with on-board processing and wireless
communication modules

77. How vehicular communications work
(Continue)
- vehicle-to-vehicle (V2V) and vehicle-to-infrastructure
(V2I) communication will be possible

79. What can VANET provide ?

80. Warnings!!!

81. traffic and road conditions

82. What can VANET provide
The VANET can provide
 Safety
 Efficiency
 Traffic and road conditions
 Road signal alarm
 Local information

83. Application Types
• Safety applications
– Used to send safety messages
• Nonsafety applications
– Provide an efficient and comfortable driving experience
– Categories
• Traffic management
– Used to improve traffic flow and resolve congestion on the road
• Infotainment
– Used for information and entertainment purposes
– Providing Internet access to passengers
» Data storage
» Video streaming
» Video calling

84. Challenges
• Intermittent connectivity
– Control and management of network connection among
vehicles and infrastructure is a key challenge
– Intermittent connections due to the high mobility of vehicles or
high packet loss in vehicular networks must be avoided
• High mobility and location awareness
– Future VANETs require high mobility and location awareness of
the vehicles participating in communication
– Each vehicle should have the correct position of other vehicles
in the network to cope with an emergency situation
• Heterogeneous vehicle management
– Large number of heterogeneous smart vehicles
– Management of heterogeneous vehicles and their sporadic
connections is another challenge of future VANETs

85. • Security
– Always a risk to the privacy of user’s data content and
location
– Vehicles communicating within the infrastructure
should allow users to decide what information should
be exchanged and what information should be kept
private
– Privacy can be assured by examining sensitive data
locally, instead of sending it to the cloud for analysis
• Support of network intelligence
– In future VANETs, there will be a large number of
sensors installed in vehicles, and the edge cloud
collects and preprocesses the collected data before
sharing them with other parts of the network

86. MANET Vs VANET
MANET VANET
MANET – Mobile AdhocNETwork VANET- Vehicular AdhocNETworks
Nodes moves randomly Nodes moves regularly
Mobility is low Mobility is high
Reliability is medium Reliability is high
Node lifetime depends on power source Node lifetime depends on vehicle life time
Network topology is sluggish and slow Network topology is frequent and fast

87. SECURITY ISSUES
• Lack of Physical boundary
– Mobile node act as a router and forwards packets
• Network boundaries become blurred
– Distinction between internal and external nodes
• Difficult to
– Deploy firewalls
– Monitor the incoming traffic
• Low Power RF transmissions
– Malicious node transmit and monopolise the medium
continuously
• Cause neighboring nodes to wait endlessly for message
transmission
– Signal Jamming leads to Denial-of-Service(DoS) attack

88. • Limited computational capabilities
– Reason
• Difficult to deploy compute-intensive security solutions
– Setting up a public key cryptosystem
• Inability to encrypt messages
– Invites a host of security attacks
• Limited power supply
– Attacker attempt to exhaust batteries by causing
• Unnecessary Transmissions
• Excessive computations

89. ATTACKS ON AD HOC NETWORKS
• Types of security attacks
• Passive Attack
– Target to monitor and steel the data exchanged in the network
without disrupting the network operations
– Example
• Snooping
• Eavesdropping
• Traffic Analysis
• Monitoring
• Active Attack
– Destructive and disturbs the normal functionality of the network
– Example
• Wormhole
• Black Hole
• Grey Hole
• Resource Consumption
• Routing Attacks