Ad -hoc Net works Mobile Communications

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1. 02/28/251
WIRELESS AD-HOC
NETWORKS
Presented By,
Mr.S.Palanivel Rajan,
Assistant Professor,
Department of ECE,
Kamaraj College of Engineering and Technology,
Virudhunagar, Tamilnadu.

2. 02/28/25
Cellular and Ad Hoc Wireless Networks
The following figure represents different wireless networks.
•Infrastructure: cellular wireless networks
•Ad hoc: wireless sensor networks
•Hybrid: mesh networks
Cellular Wireless
Networks
Hybrid Wireless
Networks
Wireless Mesh
Networks
Wireless Sensor
Networks
2

3. 02/28/25
What is an Ad hoc Network
3
Collection of mobile wireless nodes forming a network
without the aid of any infrastructure or centralized
administration
Nodes have limited transmission range
Nodes act as a routers

4. 02/28/254
Ad Hoc Networks
Ad hoc -- a Latin phrase which means "for this
[purpose]".
An autonomous system of mobile hosts
connected by wireless links, often called Mobile
Ad hoc NETworks (MANETs)

5. 02/28/25
Why Ad Hoc Networks ?
Setting up of fixed access points and backbone infrastructure
is not always viable
Infrastructure may not be present in a disaster area or war zone
Infrastructure may not be practical for short-range radios;
Bluetooth (range ~ 10m)
Ad hoc networks:
Do not need backbone infrastructure support
Are easy to deploy
Useful when infrastructure is absent, destroyed or impractical
5

6. 02/28/256
Characteristics of MANET
No fixed infrastructure
Dynamic changing topology
Mobile devices join/leave the network unexpectedly;
they can also move freely
Energy-constrained
Limited bandwidth
Each node also serves as router
Help to relay packets received from neighbors
Interoperation with the Internet

7. 02/28/25
Scalable, reliable, consistent,
distributed service
7
Calendar+ service
Integrate dynamic traffic & schedule
Doctor prescription service
track health indicators
Doctor write prescription
Follow me kiosk service
receive and transmit messages
Fridge & shopping service
Fridge records stock
Suggests shopping based on recipe
Shopping guide in store
Sensor services
exercise monitor
biometrics
traffic information
services
Sensors mobile devices

Services while on move

8. 02/28/25
Comparison between Cellular & Ad Hoc
Wireless Networks
Cellular Networks Ad Hoc Wireless Networks
Fixed infrastructure-based Infrastructure less
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)
Frequent path breaks due to mobility
High cost and time of deploymentQuick and cost-effective deployment
Reuse of frequency spectrum through
geographical channel reuse
Dynamic frequency reuse based on carrier
sense mechanism
Easier to employ bandwidth reservationBandwidth reservation requires complex
medium access control protocols

9. 02/28/25
Applications of Ad hoc Networks
Military applications
•Ad hoc wireless networks is useful in establishing communication in a
battle field.
Collaborative and Distributed Computing
•A group of people in a conference can share data in ad hoc networks.
•Streaming of multimedia objects among the participating nodes.
Emergency Operations
•Ad hoc wireless networks are useful in emergency operations such as search
and rescue, and crowd control.
9

10. 02/28/2510
Comparison
MANETs vs. Wired networks
In MANETs, each node also works as router for
forwarding packets
In wired networks, routers perform routing task
MANETs vs. Managed wireless networks
No infrastructure in MANETs
Special node known as access point (AP) in managed
wireless networks

11. 02/28/2511
A MANET Example

12. 02/28/25
MANET: Mobile Ad hoc Networks
12
A collection of wireless mobile nodes dynamically forming a
network without any existing infrastructure and the relative
position dictate communication links (dynamically changing).

13. 02/28/25
Mobile Ad Hoc Networks (MANET)
Host movement frequent
Topology change frequent
No cellular infrastructure. Multi-hop wireless links.
Data must be routed via intermediate nodes.
A
B
A
B
13

14. 02/28/25
Applications
Personal area networking
cell phone, laptop, ear phone, wrist watch
Military environments
soldiers, tanks, planes
Civilian environments
taxi cab network
meeting rooms
sports stadiums
boats, small aircraft
Emergency operations
search-and-rescue
policing and fire fighting
14

15. 02/28/25
Traffic networks
“Smart cars” and “smart roads”
Onboard systems “talk” to the
“road”:
Map obstacles and delays
Obtain maps
Inform the road of its actions
15

16. 02/28/25
Military applications
Combat regiment in the field
Perhaps 4000-8000 objects in constant
unpredictable motion…
Intercommunication of forces
Proximity, function, plan of battle
Special issues
Low probability of detection
Random association and topology
16

17. 02/28/2517
Mobile Devices
Laptop computers
Pagers, cellular phones, PDAs
In-car navigators -Dash Express
Dash units talk to each other and form
a network that connects to the Internet
Traffic speed data is sent back to the company,
then broadcast back to all local dash units
Sensors

18. 02/28/2518
Wireless Sensor Network (WSN)
An emerging application area for MANETs
A collection of cheap to manufacture, stationary,
tiny sensors
Network lifetime -- power as a major driving
issue
Battlefield surveillance, environment monitoring,
health care, etc.

19. 02/28/2519
WSN Example

20. 02/28/2520
Security Requirements in MANETs

21. 02/28/2521
Security Solution Constraints
Lightweight
Decentralized
Reactive
Fault-tolerant

22. 02/28/2522
Challenges
No infrastructure
Peer-to-peer architecture with multi-hop routing
Mobile device physical vulnerability
Stringent resource constraints
Wireless medium
Node mobility

23. 02/28/2523
Threats

24. 02/28/2524
MANETs Security
Routing security
Data forwarding security
Link layer security
Key management
Intrusion detection systems (IDSs)

25. 02/28/25
Routing and Mobility
Finding a path from a source to a destination
Issues
Frequent route changes
amount of data transferred between route changes may be much smaller
than traditional networks
Route changes may be related to host movement
Low bandwidth links

Goal of routing protocols
decrease routing-related overhead
find short routes
find “stable” routes (despite mobility)
25

26. 02/28/25
Mobile IP
Router
1
Router
3
Router
2
S
MH
Home
agent
26

27. 02/28/25
Mobile IP
Router
1
Router
3
Router
2
S MH
Home agent
Foreign agent
move
Packets are tunneled
using IP in IP
27

28. 02/28/25
Routing Protocols
Proactive protocols
Traditional distributed shortest-path protocols
Maintain routes between every host pair at all times
Based on periodic updates; High routing overhead
Example: DSDV (destination sequenced distance vector)
Reactive protocols
Determine route if and when needed
Source initiates route discovery
Example: DSR (dynamic source routing)
Hybrid protocols
Adaptive; Combination of proactive and reactive
Example : ZRP (zone routing protocol)
28

29. 02/28/25
Dynamic Source Routing (DSR)
When node S wants to send a packet to node D, but does not
know a route to D, node S initiates a Route discovery
Source node S floods Route Request (RREQ)
Each node appends own identifier when forwarding RREQ
29

30. 02/28/25
Route Discovery in DSR[1/6]
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
Represents a node that has received RREQ for D from S
M
N
L
30

31. 02/28/25
Route Discovery in DSR[2/6]
B
A
S
E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
Y
Broadcast transmission
M
N
L
[S]
[X,Y] Represents list of identifiers appended to RREQ
31

32. 02/28/25
Route Discovery in DSR[3/6]
B
A
S
E
F
H
J
D
C
G
I
K
• Node H receives packet RREQ from two neighbors:
potential for collision
Z
Y
M
N
L
[S,E]
[S,C]
32

33. 02/28/25
Route Discovery in DSR[4/6]
B
A
S
E
F
H
J
D
C
G
I
K
• Node C receives RREQ from G and H, but does not forward
it again, because node C has already forwarded RREQ once
Z
Y
M
N
L
[S,C,G]
[S,E,F]
33

34. 02/28/25
Route Discovery in DSR[5/6]
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
M
• Nodes J and K both broadcast RREQ to node D
• Since nodes J and K are hidden from each other, their
transmissions may collide
N
L
[S,C,G,K]
[S,E,F,J]
34

35. 02/28/25
Route Discovery in DSR[6/6]
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
• Node D does not forward RREQ, because node D
is the intended target of the route discovery
M
N
L
[S,E,F,J,M]
35

36. 02/28/25
Destination D on receiving the first RREQ, sends a Route
Reply (RREP)
RREP is sent on a route obtained by reversing the route
appended to received RREQ
RREP includes the route from S to D on which RREQ was
received by node D
36

37. 02/28/25
Route Reply in DSR
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
RREP [S,E,F,J,D]
Represents RREP control message
37

38. 02/28/25
Node S on receiving RREP, caches the route included in the
RREP
When node S sends a data packet to D, the entire route is
included in the packet header
hence the name source routing
Intermediate nodes use the source route included in a packet
to determine to whom a packet should be forwarded
38

39. 02/28/25
Data Delivery in DSR
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
DATA [S,E,F,J,D]
Packet header size grows with route length
39

40. 02/28/25
Dynamic Source Routing: Advantages
Routes maintained only between nodes who need to
communicate
Reduces overhead of route maintenance
Route caching can further reduce route discovery overhead
A single route discovery may yield many routes to the
destination, due to intermediate nodes replying from local
caches
40

41. 02/28/25
Ad Hoc On-Demand Distance Vector
Routing (AODV)
DSR includes source routes in packet headers
Resulting large headers can sometimes degrade performance
Particularly when data contents of a packet are small
AODV attempts to improve on DSR by maintaining routing
tables at the nodes, so that data packets do not have to
contain routes
AODV retains the desirable feature of DSR that routes are
maintained only between nodes which need to communicate
41

42. 02/28/25
Routing in AODV
Route Requests (RREQ) are forwarded in a manner similar
to DSR
When a node re-broadcasts a Route Request, it sets up a
reverse path pointing towards the source
AODV assumes symmetric (bi-directional) links
When the intended destination receives a Route Request, it
replies by sending a Route Reply (RREP)
Route Reply travels along the reverse path set-up when
Route Request is forwarded
42

43. 02/28/25
Route Requests in AODV[1/3]
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
Represents a node that has received RREQ for D from S
M
N
L
43

44. 02/28/25
Route Requests in AODV [2/3]
B
A
S
E
F
H
J
D
C
G
I
K
Represents transmission of RREQ
Z
Y
Broadcast transmission
M
N
L
44

45. 02/28/25
Route Requests in AODV [3/3]
B
A
S
E
F
H
J
D
C
G
I
K
Represents links on Reverse Path
Z
Y
M
N
L
45

46. 02/28/25
Reverse Path Setup in AODV
B
A
S
E
F
H
J
D
C
G
I
K
• Node C receives RREQ from G and H, but does not forward
it again, because node C has already forwarded RREQ once
Z
Y
M
N
L
46

47. 02/28/25
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
47

48. 02/28/25
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
• Node D does not forward RREQ, because node D
is the intended target of the RREQ
M
N
L
48

49. 02/28/25
B
A
S
E
F
H
J
D
C
G
I
K
Z
Y
M
N
L
Forward links are setup when RREP travels along
the reverse path
Represents a link on the forward path
49

50. 02/28/25
Route Request and Route Reply
Route Request (RREQ) includes the last known sequence number for the
destination
An intermediate node may also send a Route Reply (RREP) provided that it
knows a more recent path than the one previously known to sender
Intermediate nodes that forward the RREP, also record the next hop to
destination
A routing table entry maintaining a reverse path is purged after a timeout
interval
A routing table entry maintaining a forward path is purged if not used for a
active_route_timeout interval
50

51. 02/28/25
Link Failure detection
A neighbor of node X is considered active for a routing table entry if the
neighbor sent a packet within active_route_timeout interval which was forwarded
using that entry
Neighboring nodes periodically exchange hello message
When the next hop link in a routing table entry breaks, all active neighbors are
informed
Link failures are propagated by means of Route Error (RERR) messages, which
also update destination sequence numbers
51

52. 02/28/25
Route Error
When node X is unable to forward packet P (from node S to node D) on link
(X,Y), it generates a RERR message
Node X increments the destination sequence number for D cached at node X
The incremented sequence number N is included in the RERR
When node S receives the RERR, it initiates a new route discovery for D using
destination sequence number at least as large as N
When node D receives the route request with destination sequence number N,
node D will set its sequence number to N, unless it is already larger than N
52

53. 02/28/25
AODV: Summary
Routes need not be included in packet headers
Nodes maintain routing tables containing entries only for
routes that are in active use
At most one next-hop per destination maintained at each
node
DSR may maintain several routes for a single destination
Sequence numbers are used to avoid old/broken routes
Sequence numbers prevent formation of routing loops
Unused routes expire even if topology does not change
53

54. 02/28/25
Temporally-Ordered Routing Algorithm
(TORA)
Route optimality is considered of secondary importance; longer routes may be
used
At each node, a logically separate copy of TORA is run for each destination,
that computes the height of the node with respect to the destination
Height captures number of hops and next hop
Route discovery is by using query and update packets
TORA modifies the partial link reversal method to be able to detect partitions
When a partition is detected, all nodes in the partition are informed, and link
reversals in that partition cease
54

55. 02/28/25
Destination-Sequenced Distance-Vector
(DSDV)
Each node maintains a routing table which stores
next hop, cost metric towards each destination
a sequence number that is created by the destination itself
Each node periodically forwards routing table to neighbors
Each node increments and appends its sequence number when sending its local
routing table
Each route is tagged with a sequence number; routes with greater sequence
numbers are preferred
Each node advertises a monotonically increasing even sequence number for
itself
When a node decides that a route is broken, it increments the sequence
number of the route and advertises it with infinite metric
Destination advertises new sequence number
55

56. 02/28/25
Zone Routing Protocol (ZRP)
ZRP combines proactive and reactive approaches
All nodes within hop distance at most d from a node X are
said to be in the routing zone of node X
All nodes at hop distance exactly d are said to be peripheral
nodes of node X’s routing zone
Intra-zone routing: Proactively maintain routes to all nodes
within the source node’s own zone.
Inter-zone routing: Use an on-demand protocol (similar to
DSR or AODV) to determine routes to outside zone.
56

57. 02/28/25
Zone Routing Protocol (ZRP)
Radius of routing zone = 2
57

58. 02/28/2558
Routing Protocol Attacks
Attacks using modification
Redirection by modifying route sequence number
Redirection by modifying hop count
Source route modification
Tunneling

59. 02/28/2559
Routing Protocol Attacks
Attacks using fabrication
Falsifying route errors
Broadcast falsified routes
Spoofing attacks
Rushing attacks

60. 02/28/2560
Data Forwarding Security
Threats
Eavesdropping (passive attacks)
cryptography can help to prevent but how to detect
eavesdropping is still an open research topic
Dropping data packets (similar to selfishness)
Selfish behavior on data forwarding
Drops other nodes’ packets to preserve its resources, e.g.
battery power

61. 02/28/2561
Detection Solution against Selfishness
End-to-end feedbacks
Monitoring in promiscuous mode (watchdog)
Activity-based overhearing
Mutually according admission in neighborhood
Reputation based solution
Probing

62. 02/28/2562
Key Management
Most of the solutions for secure routing and
data forwarding rely on cryptography
Key management is problematic because of
the lack of any central infrastructure
Private key infrastructure
Public key infrastructure

63. 02/28/2563
Intrusion Detection Systems (IDS’s)
Proactive solutions cannot eliminate attacks
(secure routing layer, link layer mechanism)
IDS presents a second wall of defense
Assumptions
User and programs are observable
Normal and intrusion activities can be
distinguished

64. 02/28/2564
Problems with Traditional IDS’s in
MANETs
Infrastructure less nature of MANETs
No traffic concentration points for monitoring
Resource limitation of mobile devices
Lack of clear separation between normalcy
and anomaly
as nodes move around, the topology changes;
so each node should expect different traffic pattern
from its neighbors

65. 02/28/2565
Proposed Solutions
Distributed, host-based, anomaly-based, and
cooperative

66. 02/28/2566
Wireless Sensor Network (WSN)
Security
Consists of thousands or millions of tiny devices:
signal processing circuit,
micro-controller,
wireless transmitter/receiver,
embedded sensor

67. 02/28/2567
More Stringent Performance
Requirement
More stringent performance requirement
Energy efficiency -network lifetime
Auto-organization
Scalability to a high number of nodes

68. 02/28/2568
Security Issues
Key distribution and management
Scalable to a large number of sensor nodes
Remains to be unsolved
Key pre-deployment
Shared key discovery
Path-key establishment
Alternatives
Probabilistic key sharing protocols

69. 02/28/2569
More Issues
Secure routing
Most routing protocols are quite simple in WSN,
thus more vulnerable to attacks. Some new attacks
are:
Sinkhole attacks
Hello flood attacks
Solutions
SPINS -two building block security protocols: SNEP and
µTESLA
INSENS -intrusion-tolerant routing protocol

70. 02/28/25
Security Challenges in Ad Hoc
Networks [1/2]
70
Lack of Infrastructure or centralized control
Key management becomes difficult
Dynamic topology
Challenging to design sophisticated & secure routing protocols
Communication through Radio Waves
Difficult to prevent eavesdropping
Vulnerabilities of routing mechanism
Non-cooperation of nodes
Vulnerabilities of nodes
Captured or Compromised

71. 02/28/25
Security Challenges in Ad Hoc
Networks [2/2]
71
Challenges in ad hoc network security
The nodes are constantly mobile
The protocols implemented are co-operative in nature
There is a lack of a fixed infrastructure to collect audit data
No clear distinction between normalcy and anomaly in ad hoc networks
Secure the Routing Mechanism
A mechanism that satisfies security attributes like authentication, confidentiality,
non-repudiation and integrity
Secure the Key Management Scheme
Robust key certification and key distribution mechanism

72. 02/28/2572