Dinamička distribucija sigurnosnih ključeva i koalicijski protokol IP adresa za mobilne ad hoc mreže

In mobile adhoc networks (MANETs) a tree-based dynamic address auto-configuration protocol (T-DAAP) is one of the best protocols designed for address assignment as far as the network throughput and packet delays are concerned. Moreover, MANET security is an important factor for many applications given that any node can listen to the channel and overhear the packets being transmitted. In this paper, we merge the address assignment with the security key delivery into one protocol, such that a node in the MANET is configured with IP address and security key simultaneously. To the best of our knowledge, no single protocol provides concurrent assignment of IP addresses and security keys for MANET nodes. The proposed method, which is based on T-DAAP, shows significant enhancements in the required control packets needed for assigning network nodes IP addresses and security keys, MAC layer packets, total end-to-end delay, and channel throughput over those obtained when using separate protocols. Additionally, it provides not only efficient security keys to the nodes from the first moment they join the network, but also secure delivery of the address and security key to all participating nodes. It is noteworthy to mention that providing a complete security model for MANET to detect and countermeasure network security threats and attacks is beyond the scope of our proposed protocol.Kod mobilnih ad hoc mreža (MANET) dinamički protokol za autokonfiguraciju adresa baziran na stablu (T-DAAP) je jedan od najboljih protokola dizajniranih za dodjelu adresa iz perspektive propusnosti mreže i i kašnjenja paketa. štoviše, sigurnost MANET-a je važan faktor za mnoge aplikacije s obzirom da bilo koji čvor može osluškivati kanal i slučajno čuti pakete koji se šalju. U ovom radu, dodjela adresa i dostava sigurnosnih ključeva spojeni su u jedan protokol tako da je čvor u MANET-u konfiguriran simultano s IP adresom i sigurnosnim ključem. Prema saznanjima autora, niti jedan postojeći protokol ne pruža istovremeno dodjeljivanje IP adrese i sigurnosnog ključa za MANET čvorove. Predložena metoda, koja se bazira na T-DAAP-u, pokazuje značajna poboljšanja u odnosu na metode koje koriste odvojene porotokole, kod traženih kontrolnih paketa koji su potrebni za dodjeljivanje IP adresa i sigurnosnih ključeva čvorovima mreže, MAC paketa, ukupnog end-to-end kašnjenja i propusnosti kanala. Dodatno pruža ne samo efikasne sigurnosne ključeve čvorovima od trenutka kad se priključe mreži, nego i sigurno dostavljanje adrese i sigurnosnog ključa svim čvorovima koji sudjeluju u mreži. Važno je spomenuti da je pružanje cjelokupnog sigurnosnog modela za MANET koji detektira dodatno i protumjere prijetnjama i napadima na sigurnost mreže izvan dosega predloženog protokola

Scalable Address Allocation Protocol for Mobile Ad Hoc Networks

International audienceIn this paper, we present for mobile ad hoc networks an efficient distributed address allocation protocol which is immune to topology changes caused by node's mobility. Contrary to the common belief that mobility makes protocol design more difficult, we show that node's mobility can, in fact, be useful to provide efficient address allocation in ad hoc networks. In our protocol, each node that has been assigned an address manages a disjoint subset of free addresses independently. By taking advantage of node mobility, we can achieve roughly even distribution of free addresses amongst nodes in the system, which enables a new joining node to be configured by its neighbors via only local communication. Theoretical analysis and extensive simulation results are presented. We show that most of the address allocation requests can be processed in a timely fashion via local communication in the requester's neighborhood with time and message complexity in the order of node's degree, regardless of the network size

On backoff mechanisms for wireless Mobile Ad Hoc Networks

Since their emergence within the past decade, which has seen wireless networks being adapted to enable mobility, wireless networks have become increasingly popular in the world of computer research. A Mobile Ad hoc Network (MANET) is a collection of mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure. MANETs have received significant attention in recent years due to their easiness to setup and to their potential applications in many domains. Such networks can be useful in situations where there is not enough time or resource to configure a wired network. Ad hoc networks are also used in military operations where the units are randomly mobile and a central unit cannot be used for synchronization. The shared media used by wireless networks, grant exclusive rights for a node to transmit a packet. Access to this media is controlled by the Media Access Control (MAC) protocol. The Backoff mechanism is a basic part of a MAC protocol. Since only one transmitting node uses the channel at any given time, the MAC protocol must suspend other nodes while the media is busy. In order to decide the length of node suspension, a backoff mechanism is installed in the MAC protocol. The choice of backoff mechanism should consider generating backoff timers which allow adequate time for current transmissions to finish and, at the same time, avoid unneeded idle time that leads to redundant delay in the network. Moreover, the backoff mechanism used should decide the suitable action to be taken in case of repeated failures of a node to attain the media. Further, the mechanism decides the action needed after a successful transmission since this action affects the next time backoff is needed. The Binary exponential Backoff (BEB) is the backoff mechanisms that MANETs have adopted from Ethernet. Similar to Ethernet, MANETs use a shared media. Therefore, the standard MAC protocol used for MANETs uses the standard BEB backoff algorithms. The first part of this work, presented as Chapter 3 of this thesis, studies the effects of changing the backoff behaviour upon a transmission failure or after a successful transmission. The investigation has revealed that using different behaviours directly affects both network throughput and average packet delay. This result indicates that BEB is not the optimal backoff mechanism for MANETs. Up until this research started, no research activity has focused on studying the major parameters of MANETs. These parameters are the speed at which nodes travel inside the network area, the number of nodes in the network and the data size generated per second. These are referred to as mobility speed, network size and traffic load respectively. The investigation has reported that changes made to these parameters values have a major effect on network performance. Existing research on backoff algorithms for MANETs mainly focuses on using external information, as opposed to information available from within the node, to decide the length of backoff timers. Such information includes network traffic load, transmission failures of other nodes and the total number of nodes in the network. In a mobile network, acquiring such information is not feasible at all times. To address this point, the second part of this thesis proposes new backoff algorithms to use with MANETs. These algorithms use internal information only to make their decisions. This part has revealed that it is possible to achieve higher network throughput and less average packet delay under different values of the parameters mentioned above without the use of any external information. This work proposes two new backoff algorithms. The Optimistic Linear-Exponential Backoff, (OLEB), and the Pessimistic Linear-Exponential Backoff (PLEB). In OLEB, the exponential backoff is combined with linear increment behaviour in order to reduce redundant long backoff times, during which the media is available and the node is still on backoff status, by implementing less dramatic increments in the early backoff stages. PLEB is also a combination of exponential and linear increment behaviours. However, the order in which linear and exponential behaviours are used is the reverse of that in OLEB. The two algorithms have been compared with existing work. Results of this research report that PLEB achieves higher network throughput for large numbers of nodes (e.g. 50 nodes and over). Moreover, PLEB achieves higher network throughput with low mobility speed. As for average packet delay, PLEB significantly improves average packet delay for large network sizes especially when combined with high traffic rate and mobility speed. On the other hand, the measurements of network throughput have revealed that for small networks of 10 nodes, OLEB has higher throughput than existing work at high traffic rates. For a medium network size of 50 nodes, OLEB also achieves higher throughput. Finally, at a large network size of 100 nodes, OLEB reaches higher throughput at low mobility speed. Moreover, OLEB produces lower average packet delay than the existing algorithms at low mobility speed for a network size of 50 nodes. Finally, this work has studied the effect of choosing the behaviour changing point between linear and exponential increments in OLEB and PLEB. Results have shown that increasing the number of times in which the linear increment is used increases network throughput. Moreover, using larger linear increments increase network throughput

Topics on modelling and simulation of wireless networking protocols

The use of computer simulation to study complex systems has grown significantly over the past several decades. This is especially true with regard to computer networks, where simulation has become a widespread tool used in academic, commercial and military applications. Computer model representations of communication protocol stacks are used to replicate and predict the behavior of real world counterparts to solve a variety of problems.The performance of simulators, measured in both accuracy of results and run time, is a constant concern to simulation users. The running time for high delity simulation of large-scale mobile ad hoc networks can be prohibitively high. The execution time of propagation e ects calculations for a single transmission alone can grow unmanageable to account for all potential receivers. Discrete event simulators can also su er from excessive generation and processing of events, both due to network size and model complexity. In this thesis, three levels of abstracting the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Request to Send/Clear to Send (RTS/CTS) channel access mechanism are presented. In the process of assessing the abstractions' ability to mitigate runtimecost while retaining comparable results to that of a commercially available simulator, OPNET, the abstractions were found to be better suited to collecting one metric over another.Performance issues aside, simulation is an ideal choice for use in prototyping and developing protocols. The costs of simulation are orders of magnitude smaller than that of network testbeds, especially after factoring in the logistics, maintenance, and space required to test live networks. For instance, Internet Protocol version 6 (IPv6) stateless address autocon guration protocols have yet to be convincingly shown to cope with the dynamic, infrastructure-free environment of Mobile Ad hoc Networks (MANETs). This thesis provides a literature survey of autocon guration schemes designed for MANETs, with particular focus on a stateless autocon guration scheme by Jelger andNoel (SECON 2005). The selected scheme provides globally routable IPv6 pre xes to a MANET attached to the Internet via gateways. Using OPNET simulation, the Jelger-Noel scheme is examined with new cluster mobility models, added gateway mobility, and varied network sizes. Performance of the Jelger-Noel scheme, derived from overhead, autocon gura ion time and pre x stability metrics, was found to be highly dependent on network density, and suggested further re nement before deployment.Finally, in cases where a network testbed is used to test protocols, it is still advantageous to run simulations in parallel. While testbeds can help expose design aws due to code or hardware di erences, discrete event simulation environments can o er extensive debugging capabilities andevent control. The two tools provide independent methods of validating the performance of protocols, as well as providing useful feedback on correct protocol implementation and con guration. This thesis presents the Open Shortest Path First (OSPF) routing protocol and its MANET extensions as candidate protocols to test in simulated and emulated MANETs. The measured OSPF overhead from both environments was used as a benchmark to construct equivalent MANET representations and protocol con guration, made particularly challenging due to the wired nature of the emulation testbed. While attempting to duplicate and validate results of a previous OSPF study, limitations of the simulated implementation of OSPF were revealed.M.S., Electrical Engineering -- Drexel University, 200

A hybrid packet loss recovery technique in wireless ad hoc networks

TCP utilization in wireless networks poses certain problems due to its inability to distinguish packet losses caused by congestion from those caused by frequent wireless errors, leading to degraded network performance. To avoid these problems and to minimize the effect of intensive channel contention in wireless networks, this work presents a new Hybrid ARQ technique for reliable and efficient packets transfer in static wireless ad hoc network. It is a combination of recent FEC based Raptor coding technique with ARQ based selective retransmission method, which outperforms purely ARQ based method. In contrast to most Hybrid ARQ techniques, which usually employ a byte level FEC, we mostly use packet level FEC in our simulations for the data transfer, on top of less frequent ARQ to recover the residual errors. Existing packet level FEC methods are mostly based on simple parity check codes or Reed Solomon codes with erasure decoding; in this work we use the recent raptor codes. We also introduce the notion of adaptive redundancy which helps to achieve better average network performance and to further improve the redundancy efficiency

Message Complexity Analysis of Mobile Ad Hoc Network (Manet) Address Autoconfiguration Protocols

This dissertation proposes a novel method to perform a quantitative analysis of message complexity and applies this method in comparing the message complexity among the mobile ad hoc network (MANET) address autoconfiguration protocols. The original publications on the address autoconfiguration protocols had many incomplete parts making them insufficient to use on practical MANETs. Therefore, the first objective of the executed research was to complete the address autoconfiguration protocols by filling in all the missing gaps to make them operational. The missing procedures that were filled in have been developed based on the most logical procedures being faithful to the original protocol publications. In this dissertation, to obtain the upper bound of the message complexity of the protocols, the O-notation of a MANET group of N nodes has been applied. To asymptotically calculate the total number of messages generated by a protocol's step or procedure, an investigation on the nodes broadcasting, unicasting, relaying, and receiving messages is conducted and used in obtaining the upper bound of the message complexity for each protocol.School of Electrical & Computer Engineerin

Efficient address auto-configutation in ad hoc networks - protocol & algorithms

Mobile Ad hoc NETworks (MANETs) are an important part of mobile communications as they allow communications without the presence of an infrastructure. A MANET consists of an autonomous system of mobile devices. In contrast with infrastructure networks, MANET nodes act as hosts as well as routers. In the Internet, multi-hop communications are supported by the network layer, i.e. the Internet Protocol (IP). However, this requires the availability of a unique IP address. Due to the dynamic and decentralized nature of MANETs, and especially due to the mobility of nodes, providing and maintaining this unique IP address automatically in a decentralized way is a challenge addressed by auto-configuration protocols as part of the network layer. Several protocols to support this in fully decentralized environments as present in MANETs have been developed, e.g., the MANETConf, Buddy and Prophet protocols. However, they fail to solve the problem efficiently in scenarios where the nodes are highly mobile, e.g., as is the case with typical car-to-car applications. This thesis presents an address auto-configuration protocol that efficiently supports highly dynamic mobile ad hoc networks. This protocol, the Logical Hierarchical Addressing (LHA) protocol, focuses on the fast assigning of IP addresses to new nodes joining a MANET while minimizing the signaling overhead. Besides this, LHA introduces a solution for the merging problem ensuring, the uniqueness of IP addresses in the network when two previously independent MANETs merge. LHA is based on the idea that the address assignments can be achieved locally by the neigh-boring nodes of a requester, which in turn leads to a fast address assignment. Basically, in LHA, each configured node in a MANET is able to select, allocate and assign a unique address to a new node requesting an address that is free. By dividing the address space logically among configured nodes LHA is able to build a number of hierarchical structures of IP addresses. By this means, LHA solves efficiently the merging problem. Furthermore, the utilization of a certain assignment algorithm and specific address data structures is the key that LHA is able to solve the problem of missing IP addresses due to the departure of nodes. Because LHA is less dependent on unicast connections it reduces the signaling overhead and achieves fast address assignment. This in turn makes LHA highly suitable to the use in a wide range of scenarios, especially in those which are high mobility.Mobile Ad-Hoc-Netzwerke (MANETs) sind ein bedeutender Teil der Mobilkommunikation, da sie Kommunikation ohne das Vorhandensein von Infrastruktur erlauben. Ein MANET besteht aus einem autonomen System von mobilen Geräten. Im Gegensatz zu Infrastruktur-Netzwerken agieren MANET-Knoten als Host, ebenso wie als Router. Im Internet werden Multi-Hop-Kommunikationen durch den Netzwerk-Layer unterstützt, z.B. das Internet Protokoll (IP). Dies verlangt jedoch die Verfügbarkeit einer eindeutigen IP-Adresse. Wegen der dynamischen und dezentralen Natur von MANETs und besonders wegen der Mobilität der Knoten, ist die automatische, dezentrale Bereitstellung und Verwaltung dieser eindeutigen IP-Adresse eine Herausforderung, die durch Autokonfigurationsprotokolle als Teil des Netzwerk-Layers gelöst werden soll. Zur Unterstützung dieser dezentralen Umgebung, die durch MANET repräsentiert werden, wurden verschiedene Protokolle entwickelt, wie MANETConf, Buddy und Prophet. Allerdings verfehlen sie eine effiziente Lösung des Problems in Szenarien mit hoch-mobilen Knoten, wie z.B. bei typischen "Auto-zu-Auto"-Anwendungen. Die vorgestellte Arbeit präsentiert ein Adressenautokonfigurationsprotokoll, das hoch dynamische mobile Ad-Hoc-Netzwerke unterstützt. Dieses Protokoll, genannt "Logical Hierarchical Addressing (LHA)", konzentriert sich auf die schnelle Zuweisung von IP-Adressen für neue Knoten, die einem MANET beitreten, und minimiert gleichzeitig den Signal-Overhead. Zusätzlich stellt LHA eine Lösung zum Vereinigungsproblem von Netzwerken vor und sichert die Eindeutigkeit von IP-Adressen, wenn sich 2 vorher unabhängige MANETs vereinigen. LHA basiert auf der Idee, dass die Adresszuweisung lokal durch jeden benachbarten Knoten eines anfragenden Knotens durchgeführt werden kann, was zusätzlich zu einer schnelleren Adresszuweisung führt. In LHA kann jeder konfigurierte Knoten in einem MANET für einen neuen Knoten eine eindeutige, freie Adresse auswählen und zuweisen. Durch die logische Aufteilung des Adressbereiches zwischen den konfigurierten Knoten kann LHA eine Anzahl hierarchischer Strukturen von IP-Adressen aufbauen, wodurch LHA das Vereinigungsproblem effektiv löst. Des Weiteren ist der Einsatz eines speziellen Zuweisungsalgorithmus und spezieller Adressdatenstrukturen der Schlüssel dafür, das LHA das Problem der durch das Verschwinden von Knoten fehlenden IP-Adressen lösen kann. Da LHA weniger abhängig von Unicast-Verbindungen ist, reduziert es den Signal-Overhead und erreicht eine schnelle Adresszuweisung. Dieser Effekt bewirkt die hohe Eignung von LHA für eine Vielzahl von Szenarien, insbesondere hoch mobile Umgebungen