We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.

/pdf/spray-and-wait-an-efficient-routing-scheme-for-50seq3wqos.pdf

Spray and wait: an efficient routing scheme for intermittently connected mobile networks

Wireless vehicular communication has the potential to enable a host of new applications, the most important of which are a class of safety applications that can prevent collisions and save thousands of lives. The automotive industry is working to develop the dedicated short-range communication (DSRC) technology, for use in vehicle-to-vehicle and vehicle-to-roadside communication. The effectiveness of this technology is highly dependent on cooperative standards for interoperability. This paper explains the content and status of the DSRC standards being developed for deployment in the United States. Included in the discussion are the IEEE 802.11p amendment for wireless access in vehicular environments (WAVE), the IEEE 1609.2, 1609.3, and 1609.4 standards for Security, Network Services and Multi-Channel Operation, the SAE J2735 Message Set Dictionary, and the emerging SAE J2945.1 Communication Minimum Performance Requirements standard. The paper shows how these standards fit together to provide a comprehensive solution for DSRC. Most of the key standards are either recently published or expected to be completed in the coming year. A reader will gain a thorough understanding of DSRC technology for vehicular communication, including insights into why specific technical solutions are being adopted, and key challenges remaining for successful DSRC deployment. The U.S. Department of Transportation is planning to decide in 2013 whether to require DSRC equipment in new vehicles.

Dedicated Short-Range Communications (DSRC) Standards in the United States

In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

PORs: Proofs of Retrievability for Large Files

Vehicular networks are very likely to be deployed in the coming years and thus become the most relevant form of mobile ad hoc networks. In this paper, we address the security of these networks. We provide a detailed threat analysis and devise an appropriate security architecture. We also describe some major design decisions still to be made, which in some cases have more than mere technical implications. We provide a set of security protocols, we show that they protect privacy and we analyze their robustness and efficiency.

/pdf/securing-vehicular-ad-hoc-networks-4sgegi8hgk.pdf

Securing vehicular ad hoc networks

Communication and Control: Joint Treatment of Application-Specific Behaviour and Communication Constraints in VANETs

Protocol detection is the process of determining the application layer protocol in the context of network security monitoring, which requires a timely and precise decision to enable protocol-specific deep packet inspection. This task has proven to be complex, as isolated characteristics, like port numbers, are not sufficient to reliably determine the application layer protocol. In this paper, we analyze the Dynamic Protocol Detection mechanisms employed by popular and widespread open-source network monitoring tools. On the example of HTTP, we show that all analyzed detection mechanisms are vulnerable to evasion attacks. This poses a serious threat to real-world monitoring operations. We find that the underlying fundamental problem of protocol disambiguation is not adequately addressed in two of three monitoring systems that we analyzed. To enable adequate operational decisions, this paper highlights the inherent trade-offs within Dynamic Protocol Detection.

/pdf/attacks-on-dynamic-protocol-detection-of-open-source-network-zvnx15oe2o.pdf

Attacks on Dynamic Protocol Detection of Open Source Network Security Monitoring Tools

Karlsruher Integriertes Informations-Management - KIM

It is most likely that upcoming vehicles will be equipped with inter-vehicle communication technologies that enable neighboring (and remote) vehicles to exchange information directly (or indirectly over multiple hops) as needed. Although those technologies obviously compete against cellular approaches, inter-vehicle communication will most likely contribute to applications such as cooperative sensing or traffic information systems. In order to evaluate the effectiveness and benefit of such applications — most importantly in very large network scenarios — it is essential to understand the time-delay characteristics of data dissemination processes and to model them efficiently. In this paper, we explore an information-centric modeling approach to describe the time delay of beaconing based data dissemination. Our approach is based on the analogy of a construction kit with elementary, connectable road shapes (or “blocks”, e.g. a straight road, an intersection, or similar). The proposed concept supports arbitrary road network layouts, is extensible, and allows to improve the accuracy (and statistical correctness) of blocks over time. We further provide two elementary blocks of the construction kit: a straight road of arbitrary length for highway, rural and city scenarios, as well as an intersection. Compared to previous work, our underlying model of these blocks addresses not only application and communication related aspects, but also mobility related aspects.

Characterization and modeling of dissemination delays in inter-vehicle communication networks

Wireless local area networking (WLAN)-based communication enables vehicles to exchange information that is beyond the vehicle's and the driver's direct perception. It has the potential to support various applications for road safety and traffic efficiency, such as road hazard warning and collision avoidance. As opposed to cellular mobile networks, WLAN-based vehicular communication does not require a central control or an operator; instead it uses a decentralized and self-organizing approach. This article introduces key requirements and basic characteristics of WLAN-based vehicular communication and outlines the system architecture. Furthermore, it gives an overview of the most important technology components for WLAN-based vehicular communication, covering radio and communication protocols, security and privacy, radio resource management, and congestion control. The article concludes with an overview about standardization and an outlook on the system deployment.


Keywords:

car-to-X communication;
vehicular ad hoc networks;
dedicated short-range communication;
cooperative systems;
vehicular area network;
inter-vehicular communications;
intelligent transportation systems

Hannes Hartenstein

Papers

Communication and Control: Joint Treatment of Application-Specific Behaviour and Communication Constraints in VANETs

Attacks on Dynamic Protocol Detection of Open Source Network Security Monitoring Tools

Karlsruher Integriertes Informations-Management - KIM

Characterization and modeling of dissemination delays in inter-vehicle communication networks

Technologies—Communication: Wireless LAN‐Based Vehicular Communication