challenges in mobile ad hoc networks

8/18/2019 Challenges in Mobile Ad Hoc Networks

1/11

CHALLENGES IN MOBILE AD HOC NETWORKS

ABSTRACT:

In the near future, a pervasive computing

environment can be expected based on the

recent progresses and advances in

computing and communication technologies.

Next generation of mobile communication

will include both popular infrastructured

wireless networks and novel

infrastructureless mobile ad-hoc networks

(MAN!s". A MAN! is a collection of

wireless nodes that can d#namicall# form a

network to exchange information without

using an# pre-existing fixed network

infrastructure. $ireless ad-hoc networks are

increasingl# being used in the battlefield,

emergenc# search, rescue missions. !he

special features of MAN! bring great

opportunities together with severe

challenges. !his report describes the

concept, features, status and fundamental

problems of ad hoc networking. %pecial

attention is paid on network la#er routing

strateg# and intrusion detection in MAN!s.

1. INTRODUCTION

&ur future living environments are likel# to

be based upon information resources

provided b# the connections of various

communication networks for users. New

small devices like 'ersonal igital

Assistants ('As", mobile phones, and

laptops enhance the information processing

and accessing capabilities with mobilit#. !o

cater the needs of such devices, modern

technologies should adopt new model of

pervasive computing including new

architectures, standards, devices, services,

tools and protocols.

Mobile computing is the one of the most

important technolog# supporting pervasive

computing. Advances in both hardware and

software techni)ues have enabled the spread

of mobile hosts and wireless networking to

masses. *enerall#, there are two modes in

which wireless mobile nodes can

communicate+

1. Infrastructured+ In this mode, all the

communication among the mobile nodes

goes through a base station. A ase

station is also known as access point.

!hese base stations are connected to the

fixed infrastructure or wired networks.

. Infrastructure!ess+ !his mode of communication is known as a mobile ad

hoc network(MAN!". A MAN! is

collection of wireless nodes that can

d#namicall# form a network to exchange

De"t. I.T# AITS


2/11

information without using an# pre-

existing fixed network infrastructure.

!his is a ver# important part of

communication technolog# that supports

trul# pervasive computing, because in

man# contexts information exchange

between mobile units cannot rel# on an#

fixed network infrastructure, but on

rapid configuration of a wireless

connections on-the-fl#. A t#pical

example of this mode of communication

is people sitting in the conference room

and exchanging data among them

without an# fixed infrastructure.

. RELATED BACKGROUND

.1 MANET C$nce"t

A mobile ad hoc network is a collection of

wireless nodes that can d#namicall# be set

up an#where and an#time without using an# pre-existing network infrastructure. It is an

autonomous s#stem in which mobile hosts

connected b# wireless links are free to move

randoml#. In MAN!, nodes act both as

host and routers. !he traffic t#pes in ad hoc

networks are )uite different from those in an

infrastructured wireless network, including+

. %eer&t$&%eer+ ommunication

between two nodes, which are within

one hop.

/. Re'$te&t$&Re'$te: ommunication

between two nodes be#ond a single

hop but which maintain a stable route

between them. !his ma# be the result

of several nodes sta#ing within

communication range of each other in

a single area or possibl# moving as a

group. !he traffic is similar to

standard network traffic.

0. D(na')c Traff)c+ !his occurs when

nodes are d#namic and moving

around. 1outes must be reconstructed.

!his results in a poor connectivit# and

network activit# in short bursts.

. MANET *eatures

MAN! has the following features+

Aut$n$'$us ter')na!+ In MAN!,

each mobile host is autonomous node,

which ma# function as both a host and a

router. In other words, besides the basic

processing abilit# as a host, the mobile

nodes can also perform switching

functions as a router. %o usuall#

endpoints and switches are

indistinguishable in MAN!.

/ D)str)+uted $"erat)$n+ %ince there is

no background network for the central

control of the network operations, the

control and management of the network

is distributed among the terminals. !he

nodes involved in a MAN! should

collaborate amongst themselves and

De"t. I.T# AITS /


3/11

each node acts as a rela# as needed, to

implement functions e.g. securit# and

routing.

0 Mu!t)&,$" r$ut)n-+ asic t#pes of ad

hoc routing algorithms can be single-hop

and multi-hop. %ingle-hop MAN! is

simpler than multihop in terms of

structure and implementation, with the

cost of lesser functionalit# and

applicabilit#. $hen delivering data

packets from a source to its destination

out of the direct wireless transmission

range, the packets should be forwarded

via one or more intermediate nodes.

2 D(na')c net$r/ t$"$!$-(+ %ince the

nodes are mobile, the network topolog#

ma# change rapidl# and unpredictabl#

and the connectivit# among the

terminals ma# var# with time. MAN!

should adapt to the traffic and

propagation conditions as well as the

mobilit# patterns of the mobile network

nodes. !he mobile nodes in the network

d#namicall# establish routing among

themselves as the# move about, forming

their own network on the fl#. Moreover,

a user in the MAN! ma# not onl#

operate within the ad hoc network, but

ma# re)uire access to a public fixed

network.

3 *!uctuat)n- !)n/ ca"ac)t(+ !he nature

of high bit-error rates of wireless

connection might be more profound in a

MAN!. &ne end-to-end path can be

shared b# several sessions. !he channel

over which the terminals communicate is

sub4ect to noise, fading, and interference,

and has less bandwidth than a wired

network. In some scenarios, the path

between an# pair of users can traverse

multiple wireless links and the link

themselves can be heterogeneous. &ne

effect of the relativel# low to moderate

capacities is that congestion is t#picall#

the norm rather than the exception i.e.

aggregate application demand will likel#

approach or exceed network capacit#

fre)uentl#.

5 Ener-(&c$nstra)ned $"erat)$n+ %ome

or all of the nodes in a MAN! ma#

rel# on batteries or other means for their

energ#. %uch devices need optimi6ed

algorithms and mechanisms that

implement the computing and

communicating functions.

7 L)')ted ",(s)ca! secur)t(+ MAN!s

are generall# more prone to ph#sical

securit# threats than are fixed cable

networks. !he increased possibilit# of

eavesdropping, spoofing and denial-of-

De"t. I.T# AITS 0


4/11

service attacks should be carefull#

considered.

.0. MANET Status

Ad hoc network is not a new concept. It was

first deplo#ed in militar# in 879s.

ommercial interest in such networks has

grown recentl# due to the advancement in

the wireless communication. A new working

group for MAN! has been formed within

the Internet ngineering !ask :orce (I!:"

to investigate and develop standards for Internet routing support for mobile, wireless

I' autonomous segments and develop a

framework for running I' based protocols in

ad hoc networks.

!he recent I standard ;9/. has

increased the research interest in the field.

Man# international conferences andworkshops have been held b# e.g. I and

AM. :or instance, Mobi


5/11

The following are the desirable properties

of MANET routing protocol:

1 D)str)+uted $"erat)$n+ %ince there is no

central point like wired network, each

and ever# node in the MAN! performs

routing.

L$$" freed$'+ !hough, if not

incorporated in the routing protocol, the

!!> value could be used to prevent

packet from roaming in the network for

arbitraril# long periods of time. ut, still

this propert# is desirable for efficient use

of resources and better overall

performance.

0 De'and&+ased $"erat)$n+ Instead of

assuming a uniform traffic distributionwithin the network and maintaining

routing information between all nodes at

all times, routing algorithm should adapt

to the traffic pattern on a demand or

need basis. It should be done in such a

wa# so that it could utili6e mobile nodes

energ# and network bandwidth more

efficientl# at the cost of increased route

discover# dela#.

3 %r$act)e $"erat)$n+ !his is the

opposite of demand-based operation. It

certain contexts, the additional latenc#

demand-based operation is unacceptable.

If bandwidth and energ# resources

permit, proactive operation is desirable

in these contexts.

4 Secur)t(+ $ithout some form of

network-level or link la#er securit#, a

MAN! routing protocol is vulnerable

to man# forms of attack. It ma# be

relativel# simple to snoop network

traffic, manipulate packet headers and

redirect routing messages, within a

wireless network without appropriate

securit# provisions.

5 6S!ee"7 "er)$d $"erat)$n+ As a result of

energ# conservation, or some other need

to be inactive, nodes of a MAN! ma#

stop transmitting andor receiving for

arbitrar# time periods. A routing

protocol should be able to accommodate

such sleep periods without overl#

adverse conse)uences.

8 Un)d)rect)$na! !)n/ su""$rt+ i-

directional links are t#picall# assumed in

the design of routing algorithms, and

man# algorithms are incapable of

functioning properl# over unidirectional

links. ut, unidirectional links can and

do occur in wireless networks.

De"t. I.T# AITS 3


6/11

E9a'"!e: Ad ,$c On&de'and D)stance

;ect$r R$ut)n-

Ad ,$c On&de'and D)stance ;ect$r


7/11

:igure /. 'ropagation of 1oute 1e)uest

'acket (11C"

:igure 0. 'ath taken b# the 1oute 1epl#

'acket (11'"

0. Intrus)$n detect)$n

Intrusion detection has become ver#

important within the realm of network

securit# especiall# in the case wireless ad

hoc networks. Intrusion detection is defined

as the method to identif# Dan# set of actions

that attempt to compromise the integrit#,

confidentialit# or availabilit# of a resourceE.

It is the techni)ues that attempt to detect

intrusion into a computer or network b#

observing the actions, securit# logs, or audit

data.

*$!!$)n- are s$'e "r)'ar( assu'"t)$ns

t,at ,as t$ +e 'ade ,en $r/)n- $n

)ntrus)$n detect)$n:

?ser and program activities are

observable, that is the information

regarding the usage of a s#stem b# a

user or program must be recordable

and anal#6able.

/ Normal and intrusive behavior must

have distinct characteristics.

In order to detect an intrusion attack, one

needs to make use of a model of intrusion.

!hat is, we need to know what an Intrusion

etection %#stem (I%" should look out for.

!here are two t#pes of models emplo#ed in

current I%+

An$'a!( Detect)$n+ !he first model

bases its detection upon the profile of a

De"t. I.T# AITS 7


8/11

userFs normal behavior. It anal#6es the

userFs current session and compares

them to the profile representing the

userFs normal behavior. It raises alarm

if significant deviation is found during

the comparison of audit data and userFs

profile. !his t#pe of detection s#stem

is well suited to detect known or

previousl# not encountered attacks.

/ M)suse Detect)$n+ It bases its

detection upon comparison of userFs

session or commands with the rule

base of techni)ues used b# the

attackers previousl#. !his model looks

for known attacks in the userFs

behavior. A t#pical misuse detection

s#stem takes in audit data for anal#sis

and compares the data to large

database of known attack signatures.

M$st $f t,e IDS ta/e e)t,er a net$r/&

+ased $r ,$st>+ased a""r$ac, +ased $n

t,e s$urce $f aud)t data.

Net$r/&+ased IDS


9/11

intrusion detection algorithms must be made

to work on this partial and locali6ed

information.

:urther, there ma# not be a clear separation between normalc# and anomal# in wireless

ad hoc network. A node that sends out false

routing information could be the one that

has been compromised, or merel# the one

that is temporaril# out of s#nc due to

ph#sical movement. I ma# find it

increasing difficult to distinguish false

alarms from real intrusion.

T,e f$!!$)n- are t,e des)ra+!e features $f

Intrus)$n Detect)$n S(ste' f$r MANET:

1. !he I% should not introduce a new

weakness in the MAN!. !hat is,

the I% itself should not make a

node an# weaker than it alread# is.. An I% should run continuousl# and

remain transparent to the s#stem and

users.

0. !he I% should use as little s#stem

resources as possible to detect and

prevent intrusions. I%s that re)uire

excessive communication among

nodes or run complex algorithms are

not desirable.

3. It must be fault-tolerant in the sense

that it must be able to recover from

s#stem crashes, hopefull# recover to

the previous state, and resume the

operations before the crash.

4. Apart from detecting and responding

to intrusions, an I% should also

monitor itself and detect if it has

been compromised b# an attacker.

5. An I% should have a proper

response. In other words, an I%

should not onl# detect but also

respond to detected intrusions,

preferabl# without human

intervention.

8. Accurac# of the I% is another ma4or

factor in MAN!s. :ewer false

positives and false negatives are

desired.

?. It should interoperate with other

intrusion detection s#stems to

collaborativel# detect intrusions.

E9a'"!e: A D)str)+uted IDS

D)str)+uted IDS:

In their pioneering work on intrusion

detection in MAN!s, Ghang and >ee

describe a distributed and cooperative

intrusion detection model where ever# node

in the network participates in intrusiondetection and response H0. In this model, an

I% agent runs at each mobile node, and

performs local data collection and local

detection, whereas cooperative detection and

De"t. I.T# AITS 8


10/11

global intrusion response can be triggered

when a node reports an anomal#. It

considers abnormal updated to routing

tables.

!he internals of an I% agent are structured

into six pieces, as shown in :igure. ach

node does local intrusion detection

independentl#, and neighboring nodes

collaborativel# work on a larger scale.

Individual I% agents placed on each and

ever# node run independentl# and monitor

local activities (including user, s#stems, and

communication activities within the radio

range", detect intrusions from local traces,

and initiate responses. Neighboring I%

agents cooperativel# participate in global

intrusion detection actions when an anomal#

is detected in local data or if there is

inconclusive evidence. !he data collection

module gathers local audit traces and

activit# logs that are used b# the local

detection engine to detect local anomal#.

etection methods that need broader data

sets or re)uire collaborations among local

I% agents use the cooperative detection

engine. oth the local and global responsemodules provide intrusion response actions.

!he local response module triggers actions

local to this mobile node (e.g., an I% agent

alerting the local user", while the global one

coordinates actions among neighboring

nodes, such as the I% agents in the network

electing a remedial action. A secure

communication module provides a high-

confidence communication channel among

I% agents.

!his I% presents a distributed and

cooperative intrusion detection architecture

based on statistical anomal# detection

techni)ues. !his article was among the first

that had such a detailed distributed design.

Figure 4. An intrusion detection

system for MANETS

3. CONCLUSION

!his report describes the background

information of MAN!s, which includes

concepts, features and status. !hereafter, it

covers the two main challenges of MAN!s

i.e. 1outing and Intrusion detection in detail.Barious issues concerning different aspects

of ad hoc wireless networks are discussed.

MAN! is one of the most important and

essential technologies in current times.

De"t. I.T# AITS 9


11/11

MAN!s can be exploited in a wide area of

applications, from militar#, emergenc#

rescue, law enforcement, commercial, to

local and personal contexts. It has alread#

gained critical mass among researchers in

academia as well as in industr#. Moreover,

there is also a flurr# of activit# in the

standards bodies in this area. Man# routing

protocols designed for ad hoc networks have

been proposed as Internet raft and 1: of

I!:.

challenges in mobile ad hoc networks

Documents