Mobile Ad Hoc Networks
&
Vehicular Ad Hoc Networks
Overview
• MANETs
•
•
•
•
•
Challenges for MANETs
Routing protocols in MANETs
VANETs
What VANETs can provide?
Security requirements for VANETs
Architectures
Infrastructure
mode
Infrastructure-less/
distributed/ad-hoc
mode
What are MANETs (Mobile Ad Hoc Networks)?
• Formed by wireless hosts which may be mobile
• No pre-existing infrastructure
• Routes between nodes may potentially contain multiple hops
– Nodes act as routers to forward packets for each other
– Node mobility may cause the routes change
B
A
A
B
C
C
D
D
Why MANETs?
• Advantages: low-cost, flexibility
– Ease & Speed of deployment
– Decreased dependence on infrastructure
• Applications
– Military environments
• soldiers, tanks, planes
– Civilian environments
• vehicle networks
• conferences / stadiums
• outside activities
– Emergency operations
• search-and-rescue / policing and fire fighting
Challenges
• Collaboration
– Collaborations are necessary to maintain a MANET
and its functionality.
– How to collaborate effectively and efficiently?
– How to motivate/enforce nodes to collaborate?
• Dynamic topology
– Nodes mobility
– Interference in wireless communications
Routing Protocols: Overview
• Proactive protocols
– Determine routes independent of traffic pattern
– Traditional link-state and distance-vector routing protocols are
proactive
– Examples:
• DSDV (Dynamic sequenced distance-vector)
• OLSR (Optimized Link State Routing)
• Reactive protocols
– Maintain routes only if needed
– Examples:
• DSR (Dynamic source routing)
• AODV (on-demand distance vector)
• Hybrid protocols
– Example: Zone Routing Protocol (intra-zone: proactive; interzone: on-demand)
Routing Protocols: Tradeoff
• Latency of route discovery
– Proactive protocols may have lower latency since routes are
maintained at all times
– Reactive protocols may have higher latency because a route
from X to Y may be found only when X attempts to send to Y
• Overhead of route discovery/maintenance
– Reactive protocols may have lower overhead since routes are
determined only if needed
– Proactive protocols can (but not necessarily) result in higher
overhead due to continuous route updating
• Which approach achieves a better trade-off depends on
the traffic and mobility patterns
Dynamic Source Routing
•
J. Broch, D. Johnson, and D. Maltz, “The dynamic
source routing protocol for mobile ad hoc networks,”
Internet-Draft Version 03, IETF, October 1999.
• When node S wants to send a packet to node D, but
•
•
does not know a route to D, node S initiates a routing
process
Runs in three phases
 Route Discovery
 Route Reply
 Path Establishment
Route Discovery
 Source node S floods Route Request (RREQ)
 Each node appends own identifier when forwarding RREQ
Route Discovery in DSR
Y
Z
S
E
F
B
C
M
J
A
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G
H
K
I
D
N
Represents a node that has received RREQ for D from S
Route Discovery in DSR (contd..)
Y
Broadcast transmission
[S]
S
Z
E
F
B
C
M
J
A
L
G
H
K
I
D
N
Represents transmission of RREQ
[X,Y]
Represents list of identifiers appended to RREQ
Route Discovery in DSR (contd..)
Y
Z
S
E
[S,E]
F
B
C
A
M
J
[S,C]
H
G
K
I
L
D
N
Route Discovery in DSR (contd..)
Y
Z
S
E
[S,E,F,J]
F
B
C
M
J
A
L
G
H
K
I
D
[S,C,G,K]
N
Route Reply in DSR
•
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
Route Reply in DSR (contd..)
Y
Z
S
E
RREP [S,E,F,J,D]
F
B
C
M
J
A
L
G
H
K
I
Represents RREP control message
D
N
Route Reply in DSR (contd..)
•
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
Data Delivery in DSR
Y
DATA [S,E,F,J,D]
S
Z
E
F
B
C
M
J
A
L
G
H
K
I
Packet header size grows with route length
D
N
Some Other Routing Protocols
• Location information aided protocols
• Power-aware protocols
• Others …
• e.g., considering the stability of topology
Location-Aided Routing (LAR)
•
Y. Ko and N. Vaidya, “Location-aided routing (LAR) in
mobile ad hoc networks,” MobiCom'98.
• Exploits location information to limit scope of route request
•
flood
 Location information may be obtained using GPS
Expected Zone is determined as a region that is expected
to hold the current location of the destination
 Expected region determined based on potentially old location
information, and knowledge of the destination’s speed
•
Route requests limited to a Request Zone that contains the
Expected Zone and location of the sender node
•
B. Karp, and H. Kung, “Greedy Perimeter Stateless
Routing for Wireless Networks,” MobiCom 2000.
Power-Aware Routing
• Modification to DSR to make it power aware (for
simplicity, assume no route caching):
 Route Requests aggregate the weights of all traversed

links
Destination responds with a Route Reply to a Route
Request if
• it is the first RREQ with a given (“current”) sequence number,
•
or
its weight is smaller than all other RREQs received with the
current sequence number
Geography Adaptive Fidelity
• Each node associates itself with a square in a virtual grid
• Node in each grid square coordinate to determine who will
sleep and how long
[Y. Xu, et al. “Geography Adaptive Fidelity in Routing,”
Mobicom’2001]
Grid head
Research in Other Layers
• Transport layer
•
A survey: A. Hanbali, E. Altman, P. Nain, “A Survey of
TCP over Mobile Ad Hoc Networks (2004)”.
• Application layer
 Data management
•
e.g., B. Xu, A. Ouksel, and O. Wolfson, "Opportunistic
Resource Exchange in Inter-vehicle Ad Hoc Networks," MDM,
2004.
 Distributed algorithms
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•
•
•
clock synchronization
mutual exclusion
leader election
Byzantine agreement
VANETs
What is VANET
Vehicular Ad–Hoc Network, or VANET

a form of Mobile ad-hoc network

provide communication
- among nearby vehicles
- between vehicles
- nearby fixed equipment
Introduction

How vehicular communications work
- road-side infrastructure units (RSUs),
named network nodes, are equipped
with on-board processing and wireless
communication modules
How vehicular communications work
- vehicle-to-vehicle (V2V) and vehicle-to-infrastructure
(V2I) communication will be possible
What can VANETs provide ?
What can VANETs provide ?
The VANETs can provide





Safety
Efficiency
Traffic and road conditions
Road signal alarm
Local information
Challenges
Research directions
 Outline challenges for VANET
- availability, mobility
 Describe particular attacks
-DoS, alteration attacks
 Suggest solution towards attacks
Security Requirements for VANETs
1.
2.
3.
4.
5.
6.
7.
8.
Message Integrity
Message Non-Repudiation
Entity Authentication
Access Control Authorization
Message Confidentiality
Privacy and Anonymity
Availability
Liability Identification
Security Requirements for VANETs
(contd..)

Message Integrity
- Message must be protected from any
alteration

Message Non-Repudiation
- The sender of a message cannot deny having sent
a message

Entity Authentication
- The receiver is ensured that the sender generated a
message
- The receiver has evidence of the liveness of the sender
Security Requirements for VANETs
(contd..)

Access Control
- determined locally by policies
- authorization established what each
node is allowed to do in the network

Message Confidentiality
- the content of a message is kept
secret from those nodes that are not
authorized to access it
Security Requirements for VANETs
(contd..)

Privacy and Anonymity
- vehicular communication (VC)
systems should not disclose
any personal and private
information of their users
- any observers should not know any future
actions of other nodes
- anonymity may not be a reasonable requirement
for all entities of the vehicular communications
system
Security Requirements for VANETs
(contd..)

Availability
- protocols and services should remain
operational even in the presence of
faults

Liability Identification
- users of vehicles are liable for their deliberate or
accidental actions that disrupt the operation of other
nodes
System Model

Vehicular communications system
- Users
- Network nodes
- Authorities
System Model (contd..)

Users
-user is the owner or the
driver or a passenger
of the vehicle

Network Nodes
- processes running on computing platforms
capable of wireless communication
- Mounted on vehicles and road-side units
(RSUs)
System Model (contd..)

Authorities
- public agencies or
corporations with
administrative powers
- for example, city or state
transportation authorities
System Model (contd..)

1.
2.
3.
4.
5.
6.
VC system operational assumptions
Authorities
Vehicle Identification and Credentials
Infrastructure Identification and Credentials
User Identification and Credentials
User and Vehicle Association
Trusted Components
System Model (contd..)

Authorities
- trusted entities or nodes
- issuing and manage identities and
credentials for vehicular network
- establish two-way communication with nodes

Vehicle Identification and Credentials
- unique identity V
- a pair of private and public keys, kv and KV
- certificate CertX{KV, AV} issued by
authority X
- V denotes on-board central
processing and communication
module
System Model (contd..)
Note. From “Securing Vehicular Communications – Assumptions, Requirements, and Principles,” by P.
Papadimitratos, V. Gligor, J-P Hubaux, In Proceedings of the Workshop on Embedded Security in
Cars (ESCAR) 2006, November 2006.
Recap
• MANETs
•
•
•
•
•
Challenges for MANETs
Routing protocols in MANETs
VANETs
What VANETs can provide?
Security requirements for VANETs
Questions ??
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