Secure communication in cellular
and ad hoc environments
Bharat Bhargava
bb@cs.purdue.edu
Department of Computer Sciences,
Purdue University
This is supported by Motorola Communication
Research Lab & National Science Foundation
Team at Motorola:
Jeff Bonta
George Calcev
Benetido Fouseca
Trefor Delve
Team at Purdue University:
X. Wu
Research scientist (receives his
PhD from UC-Davis)
Y. Lu
PhD student
G. Ding
PhD student
W. Wang
PhD student
Problem statement
How to provide secure, continuous,
and efficient connectivity for a
mobile unit in a structured (cellular
based) or unstructured (ad hoc)
network environment?
3
Challenges
• Dynamic topology
– Movement, node failure, etc.
• Heterogeneous and decentralized control
• Limited resources
– Bandwidth, processing ability, energy
• Unfriendly environment
– Selfish nodes, malicious attackers
4
Research contributions
• Combining advantages of cellular systems and ad
hoc networks to enable a more secure network
structure and better performance
• Designing routing protocols for ad hoc networks
that adapt to both network topology and traffic
congestion
• Designing intruder identification protocols in ad
hoc networks
• Conducting experimental studies in heterogeneous
wireless environments and evaluating our protocols
5
Research directions
• Cellular-aided Mobile Ad Hoc Network
(CAMA)
• Adaptive and Heterogeneous Mobile
Wireless Networks
• Intruder Identification in Ad Hoc Networks
6
Cellular-aided Mobile Ad Hoc
Network (CAMA)
CAMA: Problem Statement
How to realize commercial peer-to-peer
applications over mobile wireless ad hoc
networks?
Papers:
“Integrating Heterogeneous Wireless Technologies:
Cellular-Aided Mobile Wireless Ad hoc Networks
(CAMA)”, submitted to ACM Special Issues of the
Journal on Special Topics in Mobile Networking
and Applicaitons (MONET).
8
Challenges
• Authentication and accounting
– No fixed membership
• Security concern
– Open medium without any centralized control
• Real time services
– Dynamic topology and slow routing
information distribution
9
Current Environment
Cellular network provides:
• Wide coverage
• Multiple services with single cellular ID
• Small packet service in 3G network
• Wireless terminals with different protocols
10
CAMA Description
• Integration of cellular network and ad hoc
network
• CAMA agent works as centralized server
attached to the cellular network
• CAMA agent provides ad hoc nodes
information such as authentication, routing
support, keys through cellular channel
• Data transmission uses ad hoc channel
11
CAMA Environment
12
Major Ideas
• Use signals via cellular network for ad hoc
routing and security managements
• Centralized CAMA agent provides control
over distributed ad hoc network
13
CAMA vs. ad hoc network
CAMA has advantages over pure ad hoc
networks in:
• Simple network authentication and
accounting
• Routing server for more accurate routing
decisions
• Certification authority for key distribution
• Central security check point for intrusion
detection
14
CAMA vs. cellular/WLAN
CAMA has advantages over cellular/WLAN
integrated network in:
• No extra fixed infrastructure
– No access point needed
• No ad hoc channel radio coverage limit
– Multi-hop ad hoc link
• No transmission bottleneck
– Not all traffic need going through a single node
15
Impact
• Cellular service combined with low-cost,
high-data-rate wireless service
16
Research Questions
• Feasibilities in commercial applications
requires:
– Development of routing algorithm and
protocols for multimedia service
– Investigation of CAMA vulnerabilities
– Development of security protocols for key
distribution and intrusion detection
– Evaluation of gain in ad hoc network
– Evaluation of overhead in cellular network
17
Methodology of Research
• Building algorithms and protocols
• Developing bench marks and performance metrics
on multi-media service
• Conducting experimental studies
– Using ns-2
– Using common platform simulator from Motorola Inc.
• Comparing with ad hoc routing protocols
– Ad hoc on-demand distance vector routing (AODV)
– Destination source routing (DSR)
18
Research of Interest to Motorola
• Evaluating CAMA routing in realistic simulation
environment:
– Radio environment
• Adaptive data rate determined by signal-noise-ratio (SNR)
– Node mobility
• Exponentially distributed speed
– Node density
• 400 users/sq.km to 14800 users/sq.km
– Traffic pattern
• VoIP, TCP, Video
– Inaccurate position information
• Error of 5m to 100m
19
Research of Interest to Motorola (ctn.)
• Authentication
– By CAMA agent
– By mobile nodes
• Accounting
– Charging rate
– Award to intermediate nodes
20
Research of Interest to Motorola (ctn.)
• Key assignment
– Group key assignment
• For entire ad hoc network
• For nodes along an active route
– Session key assignment
• For peer-to-peer communication
21
Research of Interest to Motorola (ctn.)
• Intrusion detection
– Information collection
• Information for different intrusions
– Malicious judging rule
• Quick malicious node elimination vs. probability of
wrong judgment
• Detection cost vs. gain
22
Adaptive and Heterogeneous
Mobile Wireless Networks
Problem statement
How to provide continuous connectivity for
a mobile unit to a network in which every
node is moving?
Papers:
“Secure Wireless Network with Movable Base Stations”, being
revised for IEICE/IEEE Joint Special Issue on Assurance
Systems and Networks.
“Study of Distance Vector Routing Protocols for Mobile Ad
Hoc Networks”, in Proceedings of IEEE International
Conference on Pervasive Computing and Communications
(PerCom), 2003.
24
Challenges
• Dynamic topology
– Movement, node failure, energy problem, etc.
• Decentralized control
• Limited bandwidth
– Congestion is typically the norm rather than the
exception. [RFC 2501]
25
Research contributions
• Routing protocols for mobile ad hoc
networks that adapt to not only network
topology, but also traffic and congestion.
• Architecture, design of protocols, and
experimental evaluation in heterogeneous
wireless environments
26
Broad impacts
• Sensor networks
• Military networks
27
Two network environments
considered
• Mobile ad hoc networks
– No centralized control
• Large scale heterogeneous wireless
networks with control in base stations
– Wireless networks with movable base stations
(WNMBS)
28
Research questions in mobile ad
hoc networks
• Development of ad hoc routing protocols that adapt
to traffic load and network congestion.
– Identify the network parameters that impact the
performance of routing protocols.
– Determine the appropriateness of on-demand and
proactive approaches (given specific routing requirements
and network parameters).
– Identify features of ad hoc networks that can be used to
improve routing.
29
Related work (routing protocol)
• Destination-Sequenced Distance Vector (DSDV) [Perkins/Bhagwat,
SigComm’94] (Nokia)
• Ad-hoc On-demand Distance Vector (AODV) [Perkins/Royer/Das,
WMCSA’99, IETF draft 98-03] (Nokia, UCSB, SUNY-Stony Brook)
• Dynamic Source Routing (DSR) [Johnson/Maltz, Mobile Computing’96,
IETF draft 03] (Rice Univ., CMU)
• Zone Routing Protocol (ZRP) [Haas/Pearlman/Samar, ICUPC’97, IETF draft
99-02] (Cornell)
• Adaptive Distance Vector (ADV) [Boppana/Konduru, InfoCom’01] (UT-San
Antonio)
• Source-Tree Adaptive Routing (STAR) [Garcia-Luna-Aceves/Spohn,
MONET’01] (UCSC, Nokia)
• Associativity-Based Routing (ABR) [Toh, Wireless Personal
Communications Journal’97] (Cambridge Univ.)
• Ad-hoc On-demand Multipath Distance Vector (AOMDV) [Marina/Das,
ICNP’01] (Univ. of Cincinnati)
30
Related work (cont’d)
Protocol
Approach
Routing information
uses
Additional
information
DSDV
Proactive
Distance Vector
DSR
On-demand
Source routing
AODV
On-demand
Distance Vector
ZRP
Hybrid
Distance Vector
ADV
Hybrid
Distance Vector
STAR
Proactive
Link State
ABR
On-demand
Distance Vector
Associativity
AOMDV
On-demand
Distance Vector
Multipath
31
Related work (performance
comparison)
• Comparison of DSDV, TORA, AODV and DSR
[Broch/Maltz/Johnson/Hu/Jetcheva,
MobiCom’98] (CMU)
• Scenario-based performance analysis of DSDV,
AODV, and DSR
[Johansson/Larsson/Hedman/Mielczarek/Degerma
rk, MobiCom’99] (Ericsson)
• Performance comparison of AODV and DSR
[Perkins/Royer/Das/Marine, IEEE Personal
Communications’01]
32
Methodology of research
• Developing benchmarks and performance
metrics for routing protocols
• Conducting experimental studies
– Determine guidelines for design
– Evaluate protocols
• Building algorithms and protocols
33
Ongoing research
• Study of proactive and on-demand
approaches
• Congestion-aware distance vector routing
protocol
• Packet loss study
34
Research study
• Investigate the proactive and on-demand approaches
– Generalize the results obtained from protocols to the
proactive and on-demand approaches
– Introduce power consumption as a performance metric
– Inject heavy traffic load
– Identify the major causes for packet drop
– Comprehensively study in various network environments
• Propose a congestion-aware routing protocol
35
Simulation experiments
• DSDV and AODV are studied by varying
network environment parameters
– Node mobility (maximum moving speed)
– Traffic load (number of connections)
– Network size (number of mobile nodes)
• Performance metrics
–
–
–
–
Packet delivery ratio
Average end-to-end delay
Normalized protocol overhead
Normalized power consumption
36
Simulation setup for
experiments
Simulator
ns-2
Examined protocols
DSDV and AODV
Simulation duration
1000 seconds
Simulation area
Transmission range
1000 m x 1000 m
250 m
Movement model
Random waypoint
Maximum speed
4 – 24 m/s
Traffic type
Data payload
Packet rate
Node pause time
Bandwidth
CBR (UDP)
512 bytes/packet
4 packets/sec
10 seconds
1 Mb/s
37
Motivation for a new proactive protocol
• The proactive protocols provide better support
for:
– Applications requiring QoS
• Timely propagate network conditions
– Intrusion and anomaly detection
• Constantly exchange the network topology information
• The proactive approach exhibits better
scalability with respect to the number of
mobile nodes and traffic load.
38
Proposed protocol: Congestion Aware
Distance Vector (CADV)
• Problem with the proactive approach
– Congestion
• Objective:
– Dynamically detect congestion and route packets through lesscrowded paths
• Method:
– Characterize congestion and traffic load by using expected delay.
– Consider expected delay at the next hop as the secondary metric
to make routing decisions.
– Allow a one-hop longer route to be chosen.
– Use destination sequence number to avoid loop.
39
Design issues
• Use MAC layer callback to detect broken link
– Quick detection
– More triggered updates
– Whether re-queue a packet
• Allowing a one-hop longer route
– A one-hop shorter route may not replace the current one if it
introduces significantly more delay.
– To avoid short-lived loop, do not replace the current route with a
longer one if they have the same sequence number.
• Deal with fluctuation
– Use randomness in routing decisions to reduce fluctuation
40
CADV
• Components:
– Real time traffic monitor
– Traffic control
– Route maintenance module
• Route update:
– When broadcasts an update, every node advertises the expected
delay of sending a packet as:
D

E[ D ] 
i
n
L
• Route maintenance
– Apply a function f(E[D], distance) to evaluate the value of a route
41
Observations of CADV
• CADV outperforms AODV and DSDV in terms
of delivery ratio
• The end-to-end delay becomes longer because
longer routers may be chosen to forward packets
• The protocol overhead of CADV is doubled
compared with that of DSDV. It is still less than
that of AODV when the network is loaded
• CADV consumes less power per delivered packet
than DSDV and AODV do
42
Characteristics of wireless networks with
movable base stations
•
•
•
•
•
Large scale
Heterogeneity
Autonomous sub-nets
Base stations have more resources
Base stations take more responsibilities
43
Research questions
• How to organize the network?
– Minimize the effect of motion
– Minimize the involvement of mobile host
• How to build routing protocol?
– IP-compliant
– Cooperate with various intra-subnet routing protocols
• How to secure communications?
– Authenticate
– Maintain authentication when a host is roaming
44
Related work
• Integrating ad hoc and cellular
– Mobile-Assisted Connection-Admission (MACA)
[Wu/Mukherjee/Chan, GlobeCom’00] (UC-Davis)
– Integrated Cellular and Ad-hoc Relaying (iCAR)
[Wu/Qiao/De/Tonguz, JSAC’01] (SUNY-Buffalo)
– Multihop Cellular Networks (MCN) [Lin/Hsu, InfoCom’00] (Taiwan)
• Mobile base station
– Distributed, dynamic channel allocation [Nesargi/Prakash, IEEE
Transactions on Vehicular Technology’02] (UT-Dallas)
• Hierarchical structure
– Multimedia support for Mobile Wireless Networks (MMWN)
[Ramanathan/Steenstrup, MONET’98] (BBN Technologies)
– Clustering scheme for hierarchical control in multi-hop wireless
networks [Banerjee/Khuller, InfoCom’01] (UMD)
45
Methodology of research
• Building architecture, developing
algorithms and protocols
– Membership management
– Inter-subnet routing
– Intra- and inter-subnet authentication
• Evaluation through experiments
46
Research results
• Hierarchical mobile wireless network
(HMWN)
– Hierarchical membership management scheme
– Segmented membership-based group routing
protocol
– Protection of network infrastructure
– Secure roaming and fault-tolerant
authentication
47
Future research plan
• Develop congestion avoidance routing
protocol for ad hoc networks.
• Conduct experiments to study the effect of
implementing congestion avoidance at
different layers.
• Conduct a series of experiments to evaluate
HMWN.
48