Wireless mobile ad hoc networks consist of mobile nodes interconnected by wireless multi-hop communication paths. Unlike conventional wireless networks, ad hoc networks have no fixed network infrastructure or administrative support. The topology of such networks changes dynamically as mobile nodes join or depart the network or radio links between nodes become unusable. In this chapter, I will introduce wireless ad hoc networks, and discuss their inherent vulnerable nature. Considering the inherent vulnerable nature of ad hoc networks, a set of security requirements is subsequently presented. The chapter also introduces the quality of service issues that are relevant for ad hoc networks.

Ad hoc networking

Conventional wireless networks require as prerequisites a fixed network infrastructure with centralized administration for their operation. In contrast, so-called (wireless) mobile ad hoc networks, consisting of a collection of wireless nodes, all of which may be mobile, dynamically create a wireless network amongst themselves without using any such infrastructure or administrative support [1, 2]. Ad hoc wireless networks are self-creating, self-organizing, and self-administering. They come into being solely by interactions among their constituent wireless mobile nodes, and it is only such interactions that are used to provide the necessary control and administration functions supporting such networks.

Mobile ad hoc networks offer unique benefits and versatility for certain environments and certain applications. Since no fixed infrastructure, including base stations, is prerequisite, they can be created and used “any time, anywhere.” Such networks could be intrinsically fault-resilient, for they do not operate under the limitations of a fixed topology.

In an ad hoc network, each node is expected to forward the packets of its immediate neighbor to a node closer to destination. Without cooperation of the nodes in the neighborhood, a packet cannot make its journey from a source to destination. If the neighboring nodes are selfish or compromised, then the correct forwarding of the packets through them may not be possible. Compromised nodes often subvert the underlying routing protocol in such a way that a packet gets forwarded to an arbitrary destination, where packets may be subjected to content modification, identity tampering, or simply dropped. This chapter examines the problem of securing the routing protocols of ad hoc networks.

Security aware routing

The desirable properties of a secure route, which are timeliness, ordering, authentication, authorization, data integrity, confidentiality, and non-repudiation are summarized in Table 7.1. The table also indicates the well known techniques that are often employed in practice in achieving these properties in a routing protocol. For example, time stamps are used to ensure timeliness and sequence numbers are used in packet headers to ensure ordering of the routing messages.

The route discovery process is an integral part of a routing protocol, which finds paths between a source–destination pair. When a route discovery process is initiated to find a path that satisfies certain specific criteria such as QoS constraints and if such a route is indeed found, then such a routing protocol is known as a QoS-aware routing protocol [1].

Security and quality of service in ad hoc wireless networks have recently become very important and actively researched topics because of a growing demand to support live streaming audio and video in civilian as well as military applications. While a couple of books have appeared recently that deal with ad hoc networks, a comprehensive book that deals with security and QoS has not yet appeared. I am confident that this book will fill that void.

The book grew out of a need to provide reading material in the form of book chapters to graduate students taking an advanced wireless networking course that I was teaching at the Virginia Polytechnic Institute and State University. Some of these book chapters then subsequently appeared as chapters in handbooks and survey papers in journals.

This book contains eight chapters in total, of which five chapters deal with various aspects of security for wireless networks. I have devoted only one chapter to the quality of service issue. Chapter 1 introduces basic concepts related to an ad hoc network, sets the scene for the entire book by discussing the vulnerabilities such networks face, and then produces a set of security requirements that these networks need to satisfy to live up to the challenges imposed by the vulnerabilities. Chapter 1 also introduces basic concepts regarding quality of service as it relates to ad hoc networks.

Ad hoc networks are vulnerable not only to attacks from outside but also from within. Moreover, these attacks can be active as well as passive. In this chapter, I will discuss the various possible attacks on wireless ad hoc networks; this will then facilitate the discussion about designing the security schemes for such attacks in subsequent chapters. The significance of the various security needs discussed in Chapter 1 now comes to the fore, since any attack essentially disrupts either the operational mechanisms, or the security mechanisms including the security apparatus.

Attack classification

Ad hoc networks are typically subjected to two different levels of attacks. In the first level of attack, the adversary focusses on disrupting the basic mechanisms of the ad hoc network, such as routing, which are essential for proper network operation, and in the second level of attacks, the adversary tries to damage the security mechanisms employed by the network, such as key management schemes or cryptographic algorithms in use. This can be one way of classifying attacks. Alternatively, attacks against ad hoc networks can be classified into two groups in a different way:

1. Passive attacks which involve only eavesdropping on the data that is being communicated in the network. Examples of passive attacks include covert channels, traffic analysis, sniffing to compromised keys, etc., and

2. Active attacks which involve specific actions performed by adversaries, for instance, the replication, modification, and deletion of exchanged data among the nodes.

Adversaries attempt to change the behavior of the operational mechanisms in active attacks while they are subtle in their activities in passive attacks.

Wireless networks are typically divided into three classes depending on their range of transmissions. We have personal area networks (PANS) that have a very low transmission range, of the order of several meters; Bluetooth happens to be the representative network or technology when wireless personal area networks are mentioned. On a slightly larger transmission scale, of the order of 100–200 meters, we have wireless local area networks (LANs), known as 802.11 or WiFi, which are very well deployed all over the world. The personal area and local area networks have been primarily designed for indoor applications. Networks that have transmission in the range of several kilometers are known as wireless wide area networks (WANs), and cellular networks of different vintages are prime examples of such networks. So any discussion of security in a wireless environment will not be complete unless the proposed security schemes for these three distinct networks are examined. In this chapter, I briefly go over the security schemes of wireless PAN, LAN, and WAN networks. For readers interested in knowing more about these topics, appropriate references are highlighted. I begin this chapter by discussing WiFi security, followed by cellular network security, and concluding with the security of personal area networks.

Wireless local area networks (IEEE 802.11) security

Introduction

A wireless local area network (WLAN) is a flexible data communication system implemented as an extension to, or as an alternative to, a wired LAN. Wireless local area networks transmit and receive data over the air via RF technology, minimizing the need for any wired connections, and in turn, combining data connectivity with user mobility.

Wireless mobile ad hoc networks consist of mobile nodes interconnected by wireless multi-hop communication paths. Unlike conventional wireless networks, ad hoc networks have no fixed network infrastructure or administrative support. The topology of such networks changes dynamically as mobile nodes join or depart the network or radio links between nodes become unusable. Supporting appropriate quality of service for mobile ad hoc networks is a complex and difficult issue because of the dynamic nature of the network topology and generally imprecise network state information, and has become an intensely active area of research in the last few years. This chapter presents the basic concepts of quality of service support in ad hoc networks for unicast communication, reviews the major areas of current research and results, and addresses some new issues. The focus is on routing issues associated with quality of service support. The chapter concludes with some observations on areas for further investigation.

Introduction

Mobile ad hoc networks offer unique benefits and versatility for certain environments and certain applications. Since a fixed infrastructure, including base stations, is not necessary, they can be created and used “any time, anywhere.” Second, such networks could be intrinsically fault-resilient, for they do not operate under the limitations of a fixed topology. Indeed, since all nodes are allowed to be mobile, the composition of such networks is necessarily time varying. Addition and deletion of nodes occur only by interactions with other nodes; no other agency is involved.

The previous chapters discussed mandatory security requirements, which include confidentiality, authentication, integrity, and non-repudiation. These, in turn, require some form of cryptography, certificates, and signatures. Some other security-related mechanisms include user authentication, explicit transaction authorization, end-to-end encryption, accepted log-on security (biometrics) instead of separate personal identification numbers (PINs) and passwords, intrusion detection, access control, logging, and audit trail. In this chapter, I present some of the security schemes that govern trust among the communicating entities. Governance of the trust can be based on principles and practices of key management in distributed networks or other means such as authentication. Additionally, this chapter discusses several well known methods that are related to key management and authentication.

The resurrecting duckling

The resurrecting duckling security model [1] has been developed to solve the secure transient association problem. An example of this would be when a person buying a remote control would not want any other person to be able to use another remote control bought at the same shop to work at his place, but then the remote control has to work for some other person who might buy it from the first owner. Like a duckling, who considers the first moving object it sees to be its mother, in the same way a device would recognize the first entity that sends it a secret key as its owner. When necessary, the owner could later clear the imprinting and let the device change its owner.

Intrusion detection has, over the last few years, assumed paramount importance within the broad realm of network security; more so in the case of wireless ad hoc networks. These are networks that do not have an underlying infrastructure and the network topology is constantly changing. The inherently vulnerable characteristics of wireless ad hoc networks make them susceptible to attacks and countering attacks might end up being too little too late. Secondly, with so much advancement in hacking, if attackers try hard enough, they will eventually succeed in infiltrating the system. This makes it important to monitor constantly (or at least periodically) what is taking place on a system and look for suspicious behavior. Intrusion detection systems (IDSs) do just that: monitor audit data, look for intrusions to the system, and initiate a proper response (e.g., email the systems administrator, start an automatic retaliation, etc.). As such, there is a need to complement traditional security mechanisms with efficient intrusion detection and response. This chapter discusses the problem of intrusion detection in mobile ad hoc networks and presents the solutions that have been proposed so far.

Introduction

Wireless ad hoc networks have been in focus within the wireless research community. Essentially, these are networks that do not have an underlying fixed infrastructure. Mobile hosts “join” in, on the fly, and create a network on their own. With the network topology changing dynamically and the lack of a centralized network management functionality, these networks tend to be vulnerable to a number of attacks.

The IEEE has created a new standard, called IEEE 802.16, that deals with providing broadband wireless access to residential and business customers, and is popularly known as WiMax [1]. The Worldwide Interoperability for Microwave Access (WiMax) is a non-profit industry trade organization that is overseeing the implementation of this standard, which is expected to replace services like Cable, DSL, and T1 line for last-mile broadband network access. It can replace these services because it has a target transmission rate that can exceed 100 Mbps. The transmission range for the WiMax devices is stated to be up to 31 miles, which also far exceeds WiFi's transmission range of approximately 100 meters [2, 3]. With such a large transmission range, a single base station is capable of providing broadband connections to even an entire city. This chapter, briefly introduces the WiMax standard and then discusses the security and privacy features of such networks.

Introduction

The WiMax standard was designed with the ability to provide quality of service (QoS); as a result it can support delay-sensitive applications and services. Since it is connection oriented, it has the ability to perform per-connection QoS, allowing it to operate in both dedicated and best-effort situations.

The WiMax standard was created to meet the growing demand for broadband wireless access (BWA). This demand has proven to be challenging for service providers due to the absence of a global standard. Currently, many service providers have created proprietary solutions based on a modified version of 802.11 instead.

We have already seen that optical networks come in a large number of various flavors. Optical networks may have different topologies, may be transparent or opaque, and may deploy time, space, and/or wavelength division multiplexing (TDM, SDM, and/or WDM). They may comprise tunable devices, for example, tunable transmitters, tunable optical filters, and/or tunable wavelength converters (TWCs). Furthermore, to improve their flexibility optical networks may make use of reconfigurable optical add-drop multiplexers (ROADMs) and/or reconfigurable optical cross-connects. We will use the term optical switching networks to refer to all the various types of flexible and reconfigurable optical networks that use any of the aforementioned multiplexing, tuning, and switching techniques. Thus, optical switching networks are single-channel or multichannel (WDM) networks whose configuration can be changed dynamically in response to varying traffic loads and network failures by controlling the state of their tunable and/or reconfigurable network elements accordingly. Optical switching networks are widely deployed in today's wide, metropolitan, access, and local area networks and can be found at every level of the existing network infrastructure hierarchy.

End-to-end optical networks

Optical switching networks have been commonly used in backbone networks in order to cope with the ever-increasing amount of traffic originating from an increasing number of users and bandwidth-hungry applications. As shown in Fig. 2.1, optical switching networks can be found not only in wide area long-haul backbone networks but they also become increasingly the medium of choice in metro(politan), access, and local area networks (Berthelon et al., 2000). As a matter of fact, both telcos and cable providers are steadily moving the fiber-to-copper discontinuity point out toward the end users at the network periphery.

In this part, we discuss and describe in great detail various switching techniques for optical wide area networks (WANs). A number of different optical switching techniques have been proposed for backbone wavelength division multiplexing (WDM) networks over the last few years. Our overview will focus on the major optical switching techniques that can be found in today's operational long-haul WDM networks or are expected to be likely deployed in future optical WANs. In our overview we do not claim to provide a comprehensive description of all proposed switching techniques. Instead, we try to focus on the major optical switching techniques and describe their underlying principles and operation at length. We believe that our overview of carefully selected optical switching techniques fully covers the different types of switching techniques available for optical WANs and helps the reader gain sufficient knowledge to anticipate and understand any of the unmentioned optical switching techniques that in most cases might be viewed as extensions or hybrids of the optical switching techniques discussed. For instance, a so-called light-trail is a generalization of a conventional point-to-point lightpath in which data can be dropped and added at any node along the path, as opposed to a lightpath where data can be added only by the source and dropped only by the destination node, respectively (Gumaste and Zheng, 2005). Another good example is fractional lambda switching (FλS) (Baldi and Ofek, 2002). FλS uses the globally available coordinated universal time (UTC) as a common time reference to synchronize all optical switches throughout the FλS network.