Electronic Business: Concepts, Methodologies, Tools, and Applications (4-Volumes) P105 potx

It is clear that the ability of a mobile ad hoc QHWZRUNWRGHOLYHUGHSHQGVJUHDWO\RQWKHWUDI¿F load, type of routing protocol used, and choice of parameter values such as buffer time.. Point-

the other hand, reactive or on-demand routing

protocols learn and maintain active routes only

When a new route is needed for a new connection,

source of the connection broadcasts,

network-wide, a route request (RREQ) The intended

destination responds by a route reply (RREP)

containing the path information This process is

called route discovery To minimize the number

of transmissions and speedup route discovery, the

intermediate nodes that have the requested route

may respond to a RREQ

The two most commonly used transport

pro-tocols are user datagram (UDP) and

transmis-sion control (TCP) protocols For compatibility

reasons, an ad hoc wireless network must support

these protocols However, TCP is tuned for use

on wired networks and does not work well for

multihop wireless networks

Despite several years of research, the

perfor-mance of current multihop wireless networks

is unpredictable To illustrate the performance

issue, we present in Figure 1 the overall network throughput of an 8-node ad hoc network with 7 constant bit rate (CBR) connections, representa-WLYHRIYRLFHRYHU,3WUDI¿FRYHU8'3WUDQVSRUW layer (Boppana, 2006) Even though nodes are stationary, the performance varies widely with time, owing to noise and interference caused by transmissions in the network

Mobility makes it harder to sustain perfor-mance in an ad hoc wireless network To illustrate the performance issues further, we simulated a 50-node mobile ad hoc network in a 1,000 m x

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& Varadhan, 1997) Each node has a transmis-sion range of 250 m and nodes move in random directions with an average speed of 10 m/s (22.5 miles/hour) and a top speed of 20 m/s We used

a 2 Mbps channel rate for easier analysis (The current WiFi technology provides various channel rates ranging from 1 Mbps to 54 Mbps, though in practice, the higher rates are used only when the communication nodes are close to each other.)

Figure 1 Throughput of a wireless ad hoc network with stationary nodes The vertical bars indicate throughputs over 1-second intervals The horizontal line indicates the throughput averaged thus far The ad hoc network is built using off-the-shelf Linksys 54G routers reprogrammed with Linux operating system Ad hoc on demand distance vector (AODV) routing protocol is used to discover and maintain routes.

First, we illustrate the available bandwidth

(BW) for a connection without taking any

conten-tion or interference for wireless channels (Dyer,

2002) The available BW is based on the number

RIKRSVUHTXLUHGWRUHDFKIURPDVSHFL¿HGVRXUFH node to its destination node

Next, we present performance of this network XQGHU&%5WUDI¿FORDG:HYDULHGWKHORDGIURP

Figure 2 Capacity of a single transport-layer connection in a simulated ad hoc network Owing to the nature of shared transmission space, the capacity of a connection varies inversely proportional to the number of hops from sender to receiver.

Figure 3 Packet delivery rates of various ad hoc network routing protocols

very low to very high, gradually, and measured the

performance of the network We simulated four

recent routing protocols: destination sequenced

distance vector (DSDV) (Perkins, 2000), adaptive

distance vector (ADV) (Boppana & Konduru,

2001), ad hoc on demand distance vector (AODV)

(Perkins, Belding-Royer, & Das, 2003), and

dynamic source routing (DSR) (Johnson, Maltz,

& Hu, 2003) The delivery rate (fraction of

in-jected packets that are delivered to destinations)

for this network with various routing protocols

is indicated in Figure 3 DSDV and ADV are

proactive routing protocols and AODV and DSR

are on demand routing protocols Two variants of

ADV are shown based on the amount of time a

packet is buffered within a node when there is no

route It is clear that the ability of a mobile ad hoc

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load, type of routing protocol used, and choice of

parameter values (such as buffer time)

Despite these performance issues, ad hoc

networks are likely to be the dominant form of

local area networks used in future for several

reasons

• Technology developments will make the

basic WiFi protocol robust and improve

nominal speeds further (Varshney, 2003)

Recently, evolving WiFi technology based

on MIMO antennas is shown to sustain

higher data rates than a fast ethernet

• Extensive ongoing research on networking

software will result in better routing and

transport protocols that will exhibit better

performance characteristics (Boppana &

Zheng, 2005; Desilva, 2004; Dyer, 2002)

• There are no alternatives to mobile ad hoc

networks for military combat situations In

fact, Department of Defense (DoD) is one

of the early and largest funding agencies for

research in this area

• Wireless networks streaming audio and

video will be ubiquitous in consumer homes

Ad hoc networks are particularly attractive

because they require no new wiring and satisfy location and space constraints easily (IEEE CCNC, 2006) Already, many con-sumers with high-speed broadband access have a WiFi-based network (in infrastructure mode using one access point or in multihop mode using additional WiFi extender de-vices) connecting multiple laptops wirelessly within their homes Apple’s Airport Express

is a commercial product designed to stream audio over WiFi channels The newer WiFi technology based on IEEE 802.11n or the ultra wideband (UWB) wireless technology will likely be used for high-resolution video streaming due to higher BW offered by this technology However, UWB will be used

to complement WiFi networks rather than replace them

• WiFi based ad hoc networks are the start-ing point to other types of networks, such

as RFID networks and vehicular ad hoc networks (VANETs) (IEEE CCNC, 2005)

In the next two sections, we address twin GH¿FLHQFLHVRIDGKRFQHWZRUNVSUHGLFWDEOHSHU-formance and security First, we describe how to make the performance of WiFi networks robust, and then how to address some of the security issues that require attention in wireless networks

MIXED WIRELESS NETWORKS

Given the weaknesses of ad hoc wireless networks, the area covered by them tends to be small Instead, PL[HGQHWZRUNVFRQVLVWLQJRI¿[HGLQIUDVWUXFWXUH nodes and mobile user nodes are suitable for a medium-range network spanning, for example,

a metropolitan area (Boppana & Zheng, 2005) Point-to-point wired, cellular, or WiMAX (based

on the IEEE 802.16 standard (IEEE 802.16, 2004) for metropolitan area wireless networks) wireless OLQNVDPRQJ¿[HGQRGHVDQGZLUHOHVVOLQNVIRU all nodes can be used for connectivity These

networks take advantage of reliability and high

bandwidth of wired infrastructure backbone, and

ÀH[LELOLW\DQGORZFRVWRIZLUHOHVVOLQNVXVLQJDG

hoc networking concepts Because these networks

make use of ad hoc networking, there is no need

IRU¿[HGQRGHVWRFRYHUDOOWKHGHVLUHGDUHD,ID

¿[HGQRGHLVXQDYDLODEOHDVDQHLJKERUDPRELOH

node can send its data through other mobile nodes

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We illustrate this with an example network

shown in Figure 4 This network has several mobile

nodes that can communicate only via WiFi links

and several relatively stationary nodes (denoted,

infrastructure nodes) with point-to-point (p2p)

links among them A network of this type can

provide multiple paths among user nodes For

example, node 8 in the upper left portion of the

network can go through 12 and 13 or A and C to

reach node 16 Ad hoc routing is used in cases when a user node is not near an infrastructure node For example, node 10 can reach node 4 via node 6

With the advent of new technologies, it is feasible to design such mixed networks The WiFi is a popular short haul (for distances less WKDQPZLUHOHVVOLQNSURWRFRO7KH¿[HGLQ-frastructure nodes and p2p links among them are QRWGLI¿FXOWWRVHWXS7KHSSOLQNVFDQEHZLUHG links or long-haul wireless links For example, the new IEEE 802.16 (IEEE 802.16, 2004) is an example of long-haul (for distances less than 10 Km) wireless link protocols The infrastructure QRGHVFDQEHDOUHDG\H[LVWLQJ¿[HGQRGHVFRQ-nected via p2p links (for example, access points connected to the Internet), or semi-permanent nodes that remain stationary for a few hours

)LJXUH $ PL[HG QHWZRUN ZLWK PRELOH XVHU DQG ¿[HG LQIUDVWUXFWXUH QRGHV GHQRWHG E\ FLUFOHV DQG diamonds, respectively The infrastructure nodes are interconnected by point-to-point links, denoted by dashed lines, for infrastructure support and to provide multiple paths All nodes are capable of using

a common wireless technology, such as WiFi The radio range of infrastructure nodes is indicated by a circular shaded region.

and have p2p links implemented using a

dif-ferent wireless technology More importantly,

elaborate design and implementation to ensure

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is not necessary, since gaps in the coverage can

be managed using ad hoc networking, provided

there is enough node density

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networks, we simulated a 60-node network in a

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network simulator (Zeng, Bagrodia, & Gerla,

7KHUHDUHRU¿[HGQRGHVDQGWKH

remaining nodes are mobile with speeds ranging

from 1 to 29 m/s The nominal WiFi link speed

is 2 Mbps, and p2p links are full-duplex 2 Mbps

7KH¿[HGQRGHVDUHSODFHGLQDJULGSDWWHUQDQG

RQO\DGMDFHQW¿[HGQRGHVDUHFRQQHFWHGWRHDFK

other by a p2p link We used ADV and AODV as

the routing protocols for the pure ad hoc network

WKHQHWZRUNZLWK¿[HGQRGHVDQGADV static

$'96PRGL¿HGYHUVLRQRI$'9WRWDNHDGYDQ-tage of p2p links where possible, for the other two

networks ADVSnF indicates the performance of

mixed network with n¿[HGQRGHV7KHGHOLYHU\

rates are given in Figure 5 (See Boppana & Zheng,

2005 for more information.)

$GGLQJDIHZSSOLQNVOLQNVZLWK¿[HG nodes) improves the delivery rate and overall SHUIRUPDQFH RI WKH QHWZRUN VLJQL¿FDQWO\ ,W LV even more illustrative to see the delivery rate, throughput, and packet latencies of a 1,000-node network in a 6 Km u 6 Km area There are 0, 9, RU¿[HGQRGHVSODFHGLQDJULGSDWWHUQZLWK RQO\DGMDFHQW¿[HGQRGHVFRQQHFWHGE\SSOLQNV 7KHQHWZRUNZLWK¿[HGQRGHVGHQRWHVWKHSXUH

ad hoc network

These results clearly illustrate the performance EHQH¿WVRIXVLQJGLIIHUHQWOLQNWHFKQRORJLHVLQD mostly WiFi based ad hoc network They also offer unique business opportunities (Markoff, 2006)

• Mixed networks are easy to set up since the number of stationary nodes required is small (2.5% in the 1,000-node network example) Owing to the use of ad hoc networking con-cepts, they are not likely to suffer the irksome gaps that are common in cellular networks

In fact, the existing cellular networks can

be improved using these techniques Several cellular networking companies are actively pursuing this type of networks to comple-ment cellular networks

Figure 5 Performance of 60-node mixed and pure ad hoc networks

Figure 6 Delivery rates of 1,000-node mixed networks

Figure 7 Throughput of 1,000-node mixed networks

Figure 8 Packet latencies for 1,000-node mixed networks

• They lower the cost of setting up a

met-ropolitan area network to the extent that

citywide organizations, such as municipal

government agencies or delivery service

companies, can set up their own mixed

network to provide wireless broadband

ac-cess without having a telecom company as

the carrier

SECURITY IN WIRELESS

NETWORKS

Besides performance, security is an important

issue in wireless ad hoc networks The traditional

security issues on the Internet are keeping data

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solution is to encrypt the data by the source

ap-plication and decrypt it by the destination

applica-tion (Schneier, 1996) Intermediate nodes cannot

examine the contents and cannot alter it without

being detected by the destination Since only

some applications need it, this is implemented as

an end-to-end solution (that is, the host

comput-ers or applications at both ends of a connection

invoke and manage the security features) These

techniques are also applicable to secure data

communication on wireless networks

In this section, we address a different type

of security problem: crippling the network with

false route information (Hu, Perrig, & Johnson,

2002; Marti, Giuli, Lai, & Baker, 2000; Zhou &

Haas, 1999;) These attacks are on the control

WUDI¿FUDWKHUWKDQGDWDWUDI¿F:LUHOHVVQHWZRUNV

are more susceptible to this type of attack than

wired networks for two reasons: (a) physical

access to a network port is not necessary with

wireless networks, (b) peer dissemination of

routing information and network topology leads

to highly leveraged, hard to detect hacker attacks

on wireless networks The issue of unauthorized

access to network can be addressed using

wire-less link-level encryption and decryption

(wire-less protected access or WPA) and server-based

authentication (Varshney, 2003) We describe the second issue in detail

7KHDWWDFNVRQFRQWUROWUDI¿FRUURXWLQJSUR-WRFROFDQEHFODVVL¿HGLQWRWZRFDWHJRULHV

• Denial of service (DoS) or resource consum-ing attack

• Falsifying routes and dropping/delaying data packets

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In a routing protocol such as AODV, route dis-coveries depend on network-wide dissemination FDOOHGÀRRGLQJRI55(4FRQWUROSDFNHWVIURPD source node seeking route to its destination node

A RREQ broadcasted by a source is rebroad-casted by its neighbors to their neighbors This is repeated until the destination receives a copy of this RREQ and responds with an RREP control packet that establishes the route between source and destination A single RREQ broadcasted by

a source node results in up to (n-1) additional broadcast transmissions in the wireless network, where n is the number of nodes in the network This feature can be exploited by a malicious node

to launch highly leveraged denial-of-service at-tacks in mobile ad hoc networks These malicious nodes behave like the normal nodes in all aspects except that they initiate frequent control packet ÀRRGV7KLVLVKDUGWRGHWHFWVLQFHDQ\QRUPDOQRGH with frequently broken routes could legitimately initiate frequent route discoveries

Figure 9 shows the loss of throughput in a 100-node mobile ad hoc network with AODV

as the routing protocol and one malicious node initiating routing attacks Even 1 RREQ/s by the malicious node causes measurable drop in throughput (Desilva & Boppana 2005)

Fortunately, a simple and inexpensive solution WRWKLVSUREOHPH[LVWV8VLQJVWDWLVWLFDOSUR¿OLQJ

of control activity of other nodes, each node can independently determine overactive nodes and effectively shut them off from causing permanent damage to network performance (Desilva &

Bop-pana 2005) With this solution implemented, the

performance of the network under attack is shown

in Figure 10 Regardless of the attack rate, the

normal network throughput is sustained

The other type of security attack on routing

protocol is based on falsifying routes by the

mali-cious node in order to place itself in the path of

an active route This often involves the malicious node claiming a better route than any other node

to reach a destination Data packets received on this route are dropped or delayed arbitrarily by the malicious node This type of attack is called the blackhole attack The impact of such attacks can be severe on network performance

Figure 9 Loss of throughput with bogus route discoveries by a malicious node in a 100-node mobile

ad hoc network The offered CBR load to network is kept constant at 300, 400, or 500 Kbps, and the throughput achieved is measured as a function of attack rate by the malicious node The attack rate of zero RREQs/second denotes the normal network

)LJXUH(IIHFWLYHQHVVRIVWDWLVWLFDOSUR¿OLQJLQWKHH[DPSOHDGKRFQHWZRUNXQGHU'R6DWWDFN

Figure 11 illustrates the impact of a blackhole

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network with AODV routing protocol The

mali-cious nodes send false RREPs in response to 1%

of RREQs they hear The detection of such an

attack is expensive

The proposed solutions to mitigate such

at-tacks use hashing and symmetric cryptographic

techniques (Hu et al 2002; Zhou & Haas 1999)

This makes the solution even more expensive

than the attack itself since each control packet

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GHYHORSHI¿FLHQWVROXWLRQVWRWKHVHGDPDJLQJEXW

low frequency attacks

RFID WIRELESS NETWORKS

Several organizations, including Wal-Mart and Proctor & Gamble (P&G), are currently testing and deploying UDGLR IUHTXHQF\ LGHQWL¿FDWLRQ (RFID) technology in their supply chains In ad-dition, the Department of Defense has mandated that its suppliers tag their products at the pallet level using RFID tags The potential advan-tages of RFID technology in the supply chain are numerous RFID technology has the ability

to provide up-to-the-minute information on sales

of items, and thus can give an accurate picture

of the inventory levels This accuracy may lead

to reduction in inventory levels, thus causing a reduction in inventory costs RFID technology

)LJXUH,PSDFWRIEODFNKROHDWWDFNRYHUWLPHQDQRGHPRELOHDGKRFQHWZRUN7KHUHDUH¿YH malicious nodes sending false RREPs to 1% of RREQs they hear The attack starts at 200 seconds and VWRSVDWVHFRQGV7KHWUDI¿FORDGLV.ESV7KHWZRWKLFNOLQHVDWDQGVHFRQGSHULRGV indicate the start and end of the attack Vertical bars indicate delivery rates for 5-second periods The jagged horizontal line indicates the average network throughput from the most recent event—start of simulation, start of attack, or end of attack

at the pallet level has the potential to automate

the distribution of goods in the supply chain

between manufacturing plants, warehouses, and

retail stores of different organizations, which in

turn might reduce labor costs RFID tags allow

companies to identify all items, thus cutting down

losses from lost or misplaced inventory

For the purposes of this section, we assume the

supply chain is comprised of the manufacturer,

distributor, retailer, and the consumer As an item

with an RFID tag moves from one location to

an-other location in the supply chain, it may be read

at several different locations in the supply chain

:HGH¿QHDQRFID transaction to be an event that

corresponds to the reading of an RFID tag by an

RFID reader Each RFID transaction generates

data including the RFID tag (EPC), the reader id,

and other relevant pieces of information

The transition of an item with an RFID tag

from the manufacturer to the consumer is depicted

in Figure 12 In this paper, we assume that the

RFID tags are applied at the item, case, and

pal-let level For some items, this hierarchy-items in

cases and cases in pallets-may not be applicable,

and for some items this hierarchy may need to be changed However, the discussion in this chapter can be readily extended to other hierarchies As

an item is manufactured, an RFID tag is placed

on the item, which generates the item creation RFID transaction at the manufacturing facility Placing an item into a case, placing the case into

a pallet, as well as loading a pallet into a delivery truck generate different RFID transactions at the manufacturing facility At the distributor’s warehouse, placing the pallet into a warehouse shelf, and loading the pallet onto a delivery truck (to be delivered to the retail store) generate RFID transactions In a retail store, events such

as shelf replenishment, movement of an item from one shelf to another (possibly because of item misplacement), and sale of an item gener-ate RFID transactions At the consumer’s home,

a futuristic model suggests that the consumer’s refrigerator (or the storage area if the item does not need to be refrigerated) will be equipped with

an RFID tag reader; this results in RFID transac-tions being generated when an item is placed in the refrigerator and when an item is taken out of

Figure 12 Transition of an item from the manufacturer to the consumer in the supply chain and the relevant RFID transactions

RFID Transactions (12) Item placement/read

in the shelf or refrigerator (13) Shelf or refrigerator replenishment

RFID Transactions

(1) Item creation

(2) Item load into a case

(3) Case load into a

pallet

(4) Pallet load into a

delivery truck

Consumer’s House

RFID Transactions

(5) Pallet placement

in the warehouse (6) Pallet load into a delivery truck

RFID Transactions (7) Pallet unload in the retail store

(8) Unpacking of a pallet (9) Unpacking of a case in the retail store (10) Item placement/read

in the retail store shelf (11) Point of sale

Retail Store Distributor’s

Warehouse Manufacturing

Facility

some applications need it, this is implemented as

an end-to-end solution (that is, the host

comput-ers or applications at both ends of a connection

invoke and manage... are applied at the item, case, and

pal-let level For some items, this hierarchy-items in

cases and cases in pallets-may not be applicable,

and for some items this hierarchy... nodes) improves the delivery rate and overall SHUIRUPDQFH RI WKH QHWZRUN VLJQL¿FDQWO\ ,W LV even more illustrative to see the delivery rate, throughput, and packet latencies of a 1,000-node