Technologies for Advanced Heterogeneous Networks

P2P file-sharing systems are susceptible to pollution attacks, whereby corrupted copies of content are aggressively introduced into the system. Recent research indicates that pollution is extensive in several file sharing systems. In this paper we propose an efficient measurement methodology for identifying the sources of pollution and estimating the levels of polluted content. The methodology can be used to efficiently blacklist polluters, evaluate the success of a pollution campaign, to reduce wasted bandwidth due to the transmission of polluted content, and to remove the noise from content measurement data. The proposed methodology is efficient in that it does not involve the downloading and analysis of binary content, which would be expensive in bandwidth and in computation/human resources. The methodology is based on harvesting metadata from the file sharing system and then processing off-line the harvested meta-data. We apply the technique to the FastTrack/Kazaa file-sharing network. Analyzing the false positives and false negatives, we conclude that the methodology is efficient and accurate.

Since sensor networks became a challenge in the network research community, the basic concept of sensor networks has been widely understood and many field experiments have been conducted. Currently, we see the full spectrum of sensor networks ranging from personal area networks to the entire earth network. In this talk, two specific applications, human-body monitoring and disaster-area surveillance, are introduced and the generality and the customization of wireless sensor networks are discussed. In addition, the details of a project on multi-robot sensor networks are explained.

We present a vision of an Intelligent Network in which users dynamically indicate their requests for services, and formulate needs in terms of Quality of Service (QoS) and price. Users can also monitor on-line the extent to which their requests are being satisfied. In turn the services will dynamically try to satisfy the user as best as they can, and inform the user of the level at which the requests are being satisfied, and at what cost. The network will provide guidelines and constraints to users and services, to avoid that they impede each others’ progress. This intelligent and sensible dialogue between users, services and the network can proceed constantly based on mutual observation, network and user self-observation, and on-line adaptive and locally distributed feedback control which proceeds at the same speed as the traffic flows and events being controlled. We review issues such as network “situational awareness”, self-organisation, and structure, and relate these concepts to the ongoing research on autonomic communication systems. We relate the search for services in the network to the question of QoS and routing. We examine the need to dynamically protect the networked system from denial of service (DoS) attacks, and propose an approch to DoS defence which uses the detection of violations of QoS constraints and the automatic throttling or dropping of traffic to protect critacl nodes. We also discuss how this vision of an Intelligent Network can benefit from techniques that have been experimented in the Cognitive Packet Network (CPN) test-bed at Imperial College, thanks to “smart packets” and reinforcement learning, which offers routing that is dynamically modified using on on-line sensing and monitoring, based on users’ QoS needs and overall network objectives.

We propose a simple multiple access control (MAC) protocol that allows survivors in disaster areas to establish contact to the base stations (BSs) provided by the rescue team. Our protocol relies on downstream broadcast single-hop wireless transmissions from the BSs to the survivors and upstream multi-hop wireless transmissions. For MAC, the protocol uses a combination of tree splitting and code division multiple access (CDMA). Compared to the single-hop approach for upstream transmissions, we show that the multi-hop approach can expend less transmission energy, especially when data aggregation is possible at relay points. In addition, the multi-hop approach requires less connection setup time. The energy and time efficiency makes the protocol attractive for communications for disaster management.

Mobile IPv6 allows mobile devices always addressable by its home address wherever it is located. In this paper the focus is given on a micro-mobility based test-bed development with improved scheme. The test-bed consists of both hardware and software including four personal computers and one laptop. The laptop is used as Mobile Node (MN), two personal computers are functioned as access points, one personal computer as Home Agent (HA) and the other one is used as Foreign Multicast Router (MR). This test-bed is used to analyze the Mobile IPv6 handover delay, packet delay and packet loss in real wireless environment. We measured two scenarios those are Mobile IPv6 handover and Enhanced Mobile IPv6 with multicast function and hierarchical design. Finally, it is concluded that the proposed handover scheme reduces the handover delay from 4.4s to 0.2s, packet delay from 0.7s to 0.109s and from 44 packet loss to zero packet loss during handover. This gives advantages of zero packet loss and lower handover delay which can significantly improve micro mobility performance 3^rd and 4^th Generation mobile telephone technology and for beyond.

With the advance of multimedia systems and wireless mobile com- munications, there has been a growing need to support multimedia services (such as mobile teleconferencing, mobile TV, telemedicine, and distance learning) using mobile multimedia technologies. Despite the research done in the field of mobile multimedia, delivery of real-time interactive video over noisy wireless channels is still a challenge for researchers. This paper presents a method for prioritising data partitioned MPEG-4 video in a way suitable for transmission over a mobile network. The effectiveness of the technique is demonstrated by examining its performance when the transport of the prioritized video streams can be accomplished using packet switching technology over the enhanced general packet radio service access network infrastructure.

Recently, multimedia and group-oriented computing become increasingly popular for the users of ad hoc networks. The study of QoS issues in MANETs is vital for supporting multimedia and real-time applications. MANETs can provide multimedia users with mobility they demand, if efficient QoS multicasting strategies were developed. In this paper, we study QoS requirements, illustrate advantages and limitations of existing QoS routing protocol and propose a QoS Multicast Routing protocol (QMR) with a flexible hybrid scheme for QoS multicast routing. The hybrid scheme contains some mechanisms that provide fix-reservation and shared-reservation bandwidth to guarantee QoS multicast routing. The proposed protocol uses forward nodes to apply QoS multicast routing from source(s) to a group of destinations and support load balancing. Analysis results show the ability of QMR to exploit residual bandwidth efficiently without effect on the reserved bandwidth and provide a balance between performance gains and design complexity.

The goal of this paper is to elaborate a framework for a comparison of two ad hoc network protocols: AODV and OLSR. We propose a model to study the reaction of two protocols on faulty links in the network. The principle idea is to test two protocols with the same useful load and the proportion of faulty links and observe the amount of traffic the two protocols will create.

Wireless routing protocols in MANET are all flat routing protocols and are thus not suitable for large scale or very dense networks because of bandwidth and processing overheads they generate. A common solution to this scalability problem is to gather terminals into clusters and then to apply a hierarchical routing, which means, in most of the literature, using a proactive routing protocol inside the clusters and a reactive one between the clusters. We previously introduced a cluster organization to allow a hierarchical routing and scalability, which have shown very good properties. Nevertheless, it provides a constant number of clusters when the intensity of nodes increases. Therefore we apply a reactive routing protocol inside the clusters and a proactive routing protocol between the clusters. In this way, each cluster has O(1) routes to maintain toward other ones. When applying such a routing policy, a node u also needs to locate its correspondent v in order to pro-actively route toward the cluster owning v. In this paper, we describe our localization scheme based on Distributed Hashed Tables and Interval Routing which takes advantage of the underlying clustering structure. It only requires O(1) memory space size on each node.

Mobile Ad hoc NETworks (MANETs) are infrastructure-free, highly dynamic wireless networks, where central administration or configuration by the user is very difficult. In hardwired networks nodes usually rely on a centralized server and use a dynamic host configuration protocol, like DHCP [7], to acquire an IP address. Such a solution cannot be deployed in MANETs due to the unavailability of any centralized DHCP server. For small scale MANETs, it may be possible to allocate free IP addresses manually. However, the procedure becomes impractical for a large-scale or open system where mobile nodes are free to join and leave. Numerous dynamic addressing schemes for ad hoc networks have been proposed. These approaches differ in a wide range of aspects, such as the usage of centralized servers or full decentralization, hierarchical structure or flat network organization, and explicit or implicit duplicate address detection. In [1] we have proposed an autoconfiguration solution for OLSR, which can detect and resolve only a single address duplication in the network. In this paper, however, we will present a complete and optimized version of the autoconfiguration solution for OLSR proposed in [1]. This solution detects and resolve duplications whatever the number of address conflicts in the network, and, as in [1], it is based on an efficient Duplicate Address Detection(DAD) algorithm which takes advantage of the genuine optimization of the OLSR routing protocol [3].

In this chapter, we discuss the improvements multipoint relays may experience by the use of mobility predictions. Multipoint Relaying (MPR) is a technique to reduce the number of redundant retransmissions while diffusing a broadcast message in the network. The algorithm creates a dominating set where only selected nodes are allowed to forward packets. Yet, the election criteria is solely based on instantaneous nodes’ degrees. The network global state is then kept coherent through periodic exchanges of messages. We propose in this chapter a novel heuristic to select kinetic multipoint relays based on nodes’ overall predicted degree in the absence of trajectory changes. Consequently, these exchanges of message may be limited to the instant when unpredicted topology changes happen. Significant reduction in the number of messages are then experienced, yet still keeping a coherent and fully connected multipoint relaying network. Finally, we present some simulation results to illustrate that our approach is similar to the MPR algorithm in terms of network coverage, number of multipoint relays, or flooding capacity, yet with a drastic reduction in the number of messages exchanged during the process.

The new wireless Internet is emerging very quickly, so does network architecture. It is encouraging to see the fast development of the new IEEE wireless technologies promising the ultimate Internet service deployment on wireless and mobile infrastructures since they would offer larger bandwidth at cheaper price compared to the telecommunication wireless radio resource. However it is disquieting to see that the TCP/IP protocol stack which is supposed to be the heart of the Internet services deployment is not evolving as fast as the wireless technologies do. Here we come up with the hard question which is the network performance of the TCP/IP architecture over wireless networks. It is probably too early to decide to replace TCP/IP by another protocol stack for wireless network support, but it is important to not ignore the problem and analyse the main drawbacks of TCP/IP in wireless networks and think about a new architecture of network communication over wireless networks. This paper provides a brief survey of the future wireless Internet, and emphasizes on new network architecture to optimize the performance of this network.

Wireless-the name says it all: ”Cut the cord”. Today there is no hotter area of development than wireless networking. Enterprizes are rapidly adopting wireless local area networks (WLANs). Driving this rapid adoption is the low-cost and inherent convenience of rapidly deployed connectivity solutions, which are not burdened by a wired infrastructure. WLAN have been in the news quite a lot, recently both from the perspective of growing popularity and in terms of security vulnerabilities that have been discovered in the wired equivalent privacy (WEP) security standard, which is supposed to ensure the security of data that flows over the networks. While wireless LANs are convenient and provide immediate connectivity, they also impose unique management, security, and mobility challenges on network. Though “connect anywhere at anytime” promise of the wireless networks is beginning to become popular; there are a plenty of confusion among prospective users when it comes to security. Because WLAN impose such significant challenges, should all 802.11 networks be considered hostile to the prospective user? Not necessarily. A well-designed wireless LAN ensures that the network is well protected and easy to manage, without sacrificing the wireless user’s ability to roam seamlessly. This is a survey paper that focuses on the catalog of security risks and countermeasures of the wireless network. We describe the standard mechanisms available for authentication of users and the protection of the privacy and integrity of the data. A basic analysis of each security countermeasure is conducted by looking at the attack techniques addressed by the mechanism. Our analysis takes into account the perspective of both insiders and outsiders.

Ad hoc networks offer novel capabilities in the mobile domain widening the mobile application field and arousing significant interest within mobile operators and industrials. Securing routing protocols for ad hoc networks appeared soon as a challenging scope for industrials and researchers’ community, since routing protocols, base of ad hoc networks, haven’t defined any prevention measure or security mechanism in their specifications. In this paper, we propose a securing solution providing the integrity of the OLSR routing messages while respecting ad hoc routing protocols characteristics and operation. The solution relies on a distributed securing scheme based on threshold cryptography features and which completely fits to the OLSR operation. Implementation proves finally the successful operation of the security model and show that additional delay is suitable to OLSR routing specifications.

When a set of servers are available for a certain client-server style service, a client selects one of the servers using some server selection algorithm. The best-server algorithm in which a client selects the best one among the available servers by some metric is widely used for performance. However, when a network fluctuation occurs, the best-server algorithm often causes a sudden shift of the server load and could amplify the fluctuation. Reciprocal algorithms in which a client selects a server with a probability reciprocal to some metric are more stable than the best-server algorithm in the face of network fluctuations but their performance is not satisfactory.

In order to investigate trade-offs between the stability and the performance in server selection algorithms, we evaluate the existing algorithms by simulation and visualize the results to capture the stability of the server load.

From the simulation results, we found that the performance problem of the reciprocal algorithms lies in selecting high-cost servers with a non-negligible probability. Therefore, we propose a 2-step server selection scheme in which a client selects a working-set out of available servers for efficiency, and then, probabilistically selects one in the working-set for resiliency. We evaluate the proposed algorithm through simulation and show that our method is adaptive to environments, easy to load-balance, scalable, and efficient.

We motivate in this paper the need for application-level proximity. This proximity is a function of network characteristics that decide on the application performance. Most of existing protocols rely on the network-level proximity as for example the one based on the delay (e.g., the delay closest peer is the best peer to contact). In this paper, we study how much the two proximity definitions differ from each other. The work consists of running extensive measurements over the PlanetLab overlay network and comparing different proximity definitions. Our major observation is that the delay proximity is not always a good predictor of quality and that other network parameters are to be considered as well based on the application requirements. Particulary, the best peer to contact is not always the delay closest one. This can be explained by our other observation, that of the slight correlation of network characteristics with each other.

Recent years, trend of researches in ad-hoc networks are routing, multicasting and optimized flooding. Focusing on data flooding in ad-hoc networks, proposed scenarios of common researches are limited due to lack of scalability. If there are lots of communication originators, it is obvious that wireless resources are inapplicable. In this study, our typical scenario is that a mobile ad-hoc network is deployed in a city area and many shops, such as shopping malls and restaurants, disseminate their commercial advertisements to the network. This paper points out the lack of scalability issues considering existing IP flooding schemes and proposes a novel application flooding scheme supporting automatic data size adaptation. In this scheme, size of flooded data is dynamically sampled depending on network congestion level so that data can be delivered in a scalable manner to all nodes using MANET.

Packet loss patterns over unidirectional satellite link provide useful information for improving the performance of applications like bulk data transfer to many recipients. In this paper, we present our observations and analysis of packet loss patterns on one-to-many multicast sessions taken over an extended period of time. We collected the packet loss data on four multicast receivers in four different geographic locations. The measurements taken demonstrate possible reasons of packet loss in both sender and receiver sides including the burstiness behavior of the channel. It is found in our result that setting priority for multicast traffic in the sender side router is one of the key factors for packet loss. We found a significant amount of bursty or consecutive packet losses contributing to the overall loss percentage while the number of occurrences of bursty loss is relatively small.

Packet-pair has been used as one of the primary means to measure network capacity. Yet, most prior proposal tools are sensitive to network status and perform poorly in heavy-loaded network. We present a novel filtering mechanism to address the negative effects of cross traffic. After split the origin set of probe pairs into two packet sets composed of the first and second packet of all pairs respectively, we select the packets with minimum one-way delay in each set and use them to reconstruct a new pair free from interference of cross traffic, from which the final capacity estimates are derived. We show the mechanism in detail and validate it in simulations as well as Internet experiments. Preliminary results show that the proposed mechanism is feasible and robust for the heavy-loaded network, which can produce accurate estimates with relatively fewer overheads compared to similar tools. Finally, we analyze the difference in the first and second packet of probe pair in depth, which argues a novel direction of the analysis of packet-pair.

The AI³ project aims to achieve effective and fair bandwidth usage of its relatively narrow satellite links by all the partners in this project and the best possible end-to-end communication quality under limited resources. It is difficult to realize them as the operation of it is shared by all the partners with heterogeneous traffic demands and policies, as the network includes many traffic engineering(TE) facilities for traffic shaping or priority queuing in various points. In this paper we monitor the retransmission rate of TCP flows in a passive mode to obtain estimated packet loss rate of each flow and partner, and try to analyze the actual reason that affects end-to-end communications in a real-world environment. The results obtained in this paper is considered as a first step of reflecting TCP retransmission monitoring to improve operation, focusing on a certain partner, ITB, who has the largest traffic demand in AI³. The effectivity of the method is approved by the experimental configuration tuning.

This paper addresses the problem of characterizing analytically the autocorrelation structure of TCP traffic. We show that, under simple models, a single TCP connection generates traffic with an exponentially decreasing autocorrelation function. However, several TCP connections sharing a given link can generate traffic with long term dependencies, under the condition that the distribution of their round trip delays is heavy tailed.