Mitigating Network Service Disruptions in High-bandwidth, Intermittently Connected, and Peer-to-Peer Networks

Users demand high-bandwidth, ubiquitous and low-cost network services. This demand has pushed ISPs and application providers to offer more bandwidth, allow users to access the Internet almost everywhere, and provide cheap or free network services using peer-to-peer networks. These three trends underlie the growing success of today's Internet. However, (1) high-bandwidth can empower more effective denial-of-service attacks; (2) Internet access is widespread, but still not ubiquitous; and (3) peer-to-peer network services need to solve the service discovery problem. This thesis addresses these three challenges. First, we tackle denial-of-service attacks. The high bandwidth available in many parts of the Internet allows denial-of-service attacks to be effective, and the large scale of the Internet makes detecting and preventing these attacks difficult. Anonymity and openness of the Internet worsens this problem because anyone can send anything to anybody. To prevent these denial-of-service attacks, we propose Permission-Based-Sending (PBS), a signaling architecture for network traffic authorization. PBS uses the explicit permission to give legitimate users the authority to send packets. Signaling is used to configure this permission in the data path. This signaling approach enables easy installation for granting authorization to flows, and allows PBS to be deployed in existing networks. In addition, a monitoring mechanism provides a second line of defense against attacks. Next, we strive to make Internet access more ubiquitous. When public transportation stations have access points to provide Internet access to passengers, public transportation becomes a more attractive travel and commute option. However, the Internet connectivity is intermittent because passengers can access the Internet only when a bus or train is within the networking coverage of an AP at a stop. To efficiently handle this intermittent network for the public transit system, we develop Internet Cache on Wheels (ICOW), a system that provides a low-cost way for bus and train operators to offer access to Internet content. Each bus and train car is equipped with a smart cache that serves popular content to passengers. The cache updates its content based on passenger requests when it is within range of Internet access points placed at bus stops, train stations or depots. This aggregated Internet access is significantly more efficient than having passengers contact Internet access points individually and ensures continuous availability of content throughout the journey. Finally, we consider peer-to-peer services. Typical service discovery mechanisms in peer-to-peer networks cause significant overhead, consuming energy and bandwidth: (1) in highly mobile networks, service discovery consumes the energy of mobile devices to discover services that newly joined members provide; and (2) peer-to-peer network systems consumes bandwidth during service discovery. To resolve and analyze these service discovery problems, (1) we design an efficient service discovery mechanism that reduces energy consumption of mobile devices; and (2) we evaluate the bandwidth consumption caused by service discovery in real-world peer-to-peer networks

Strategies of collaboration in multi-channel P2P VoD streaming

As compared to live peer-to-peer (P2P) streaming, modern P2P video-on-demand (VoD) systems have brought much larger volumes of videos and more interactive controls to the Internet users. Nevertheless, the larger number of available videos and the flexibility of allowing users to jump back and forth in a video, have led to much fewer numbers of concurrent peers watching at a similar pace, that reduces the chance for collaborative chunk supply among peers and thus significantly increases the server bandwidth cost [1]. Towards the ultimate goal of maximizing peer resource utilization, in this paper, we design effective strategies for both cross-channel and intra-channel collaborations in multi-channel P2P VoD systems, such that individual peer's resources, including download/upload bandwidths and the cache capacity, are effectively utilized to maximize the streaming qualities in all the channels. In particular, each peer actively and strategically determines the supply-and-demand imbalance in different channels, as well as that among different chunks within each video, makes use of its surplus download capacity to fetch chunks with the most need, and then serves those chunks using its idle upload bandwidth, all without impairing its own streaming quality. Our extensive trace-driven simulations show the effectiveness of our strategies in reducing the server cost while guaranteeing high streaming qualities in the entire system, even during extreme scenarios such as unexpected flash crowds. ©2010 IEEE.published_or_final_versionThe IEEE Conference and Exhibition on Global Telecommunications (GLOBECOM 2010), Miami, FL., 6-10 December 2010. In Proceedings of GLOBECOM, 2010, p. 1-

Efficient Range and Join Query Processing in Massively Distributed Peer-to-Peer Networks

Peer-to-peer (P2P) has become a modern distributed computing architecture that supports massively large-scale data management and query processing. Complex query operators such as range operator and join operator are needed by various distributed applications, including content distribution, locality-aware services, computing resource sharing, and many others. This dissertation tackles a number of problems related to range and join query processing in P2P systems: fault-tolerant range query processing under structured P2P architecture, distributed range caching under unstructured P2P architecture, and integration of heterogeneous data under unstructured P2P architecture. To support fault-tolerant range query processing so as to provide strong performance guarantees in the presence of network churn, effective replication schemes are developed at either the overlay network level or the query processing level. To facilitate range query processing, a prefetch-based caching approach is proposed to eliminate the performance bottlenecks incurred by those data items that are not well cached in the network. Finally, a purely decentralized partition-based join query operator is devised to realize bandwidth-efficient join query processing under unstructured P2P architecture. Theoretical analysis and experimental simulations demonstrate the effectiveness of the proposed approaches

Interactivity And User-heterogeneity In On Demand Broadcast Video

Video-On-Demand (VOD) has appeared as an important technology for many multimedia applications such as news on demand, digital libraries, home entertainment, and distance learning. In its simplest form, delivery of a video stream requires a dedicated channel for each video session. This scheme is very expensive and non-scalable. To preserve server bandwidth, many users can share a channel using multicast. Two types of multicast have been considered. In a non-periodic multicast setting, users make video requests to the server; and it serves them according to some scheduling policy. In a periodic broadcast environment, the server does not wait for service requests. It broadcasts a video cyclically, e.g., a new stream of the same video is started every t seconds. Although, this type of approach does not guarantee true VOD, the worst service latency experienced by any client is less than t seconds. A distinct advantage of this approach is that it can serve a very large community of users using minimal server bandwidth. In VOD System it is desirable to provide the user with the video-cassette-recorder-like (VCR) capabilities such as fast-forwarding a video or jumping to a specific frame. This issue in the broadcast framework is addressed, where each video and its interactive version are broadcast repeatedly on the network. Existing techniques rely on data prefetching as the mechanism to provide this functionality. This approach provides limited usability since the prefetching rate cannot keep up with typical fast-forward speeds. In the same environment, end users might have access to different bandwidth capabilities at different times. Current periodic broadcast schemes, do not take advantage of high-bandwidth capabilities, nor do they adapt to the low-bandwidth limitation of the receivers. A heterogeneous technique is presented that can adapt to a range of receiving bandwidth capability. Given a server bandwidth and a range of different client bandwidths, users employing the proposed technique will choose either to use their full reception bandwidth capability and therefore accessing the video at a very short time, or using part or enough reception bandwidth at the expense of a longer access latency

Enabling Large-Scale Peer-to-Peer Stored Video Streaming Service with QoS Support

This research aims to enable a large-scale, high-volume, peer-to-peer, stored-video streaming service over the Internet, such as on-line DVD rentals. P2P allows a group of dynamically organized users to cooperatively support content discovery and distribution services without needing to employ a central server. P2P has the potential to overcome the scalability issue associated with client-server based video distribution networks; however, it brings a new set of challenges. This research addresses the following five technical challenges associated with the distribution of streaming video over the P2P network: 1) allow users with limited transmit bandwidth capacity to become contributing sources, 2) support the advertisement and discovery of time-changing and time-bounded video frame availability, 3) Minimize the impact of distribution source losses during video playback, 4) incorporate user mobility information in the selection of distribution sources, and 5) design a streaming network architecture that enables above functionalities.To meet the above requirements, we propose a video distribution network model based on a hybrid architecture between client-server and P2P. In this model, a video is divided into a sequence of small segments and each user executes a scheduling algorithm to determine the order, the timing, and the rate of segment retrievals from other users. The model also employs an advertisement and discovery scheme which incorporates parameters of the scheduling algorithm to allow users to share their life-time of video segment availability information in one advertisement and one query. An accompanying QoS scheme allows reduction in the number of video playback interruptions while one or more distribution sources depart from the service prematurely.The simulation study shows that the proposed model and associated schemes greatly alleviate the bandwidth requirement of the video distribution server, especially when the number of participating users grows large. As much as 90% of load reduction was observed in some experiments when compared to a traditional client-server based video distribution service. A significant reduction is also observed in the number of video presentation interruptions when the proposed QoS scheme is incorporated in the distribution process while certain percentages of distribution sources depart from the service unexpectedly

Video-on-Demand over Internet: a survey of existing systems and solutions

Video-on-Demand is a service where movies are delivered to distributed users with low delay and free interactivity. The traditional client/server architecture experiences scalability issues to provide video streaming services, so there have been many proposals of systems, mostly based on a peer-to-peer or on a hybrid server/peer-to-peer solution, to solve this issue. This work presents a survey of the currently existing or proposed systems and solutions, based upon a subset of representative systems, and defines selection criteria allowing to classify these systems. These criteria are based on common questions such as, for example, is it video-on-demand or live streaming, is the architecture based on content delivery network, peer-to-peer or both, is the delivery overlay tree-based or mesh-based, is the system push-based or pull-based, single-stream or multi-streams, does it use data coding, and how do the clients choose their peers. Representative systems are briefly described to give a summarized overview of the proposed solutions, and four ones are analyzed in details. Finally, it is attempted to evaluate the most promising solutions for future experiments. Résumé La vidéo à la demande est un service où des films sont fournis à distance aux utilisateurs avec u

System analysis of a Peer-to-Peer Video-on-Demand architecture : Kangaroo

Architectural design and deployment of Peer-to-Peer Video-on-Demand (P2PVoD) systems which support VCR functionalities is attracting the interest of an increasing number of research groups within the scientific community; especially due to the intrinsic characteristics of such systems and the benefits that peers could provide at reducing the server load. This work focuses on the performance analysis of a P2P-VoD system considering user behaviors obtained from real traces together with other synthetic user patterns. The experiments performed show that it is feasible to achieve a performance close to the best possible. Future work will consider monitoring the physical characteristics of the network in order to improve the design of different aspects of a VoD system.El disseny arquitectònic i el desplegament de sistemes de Vídeo sota Demanda "Peer-to-Peer" que soporten funcionalitats VCR està captant l'interès d'un nombre creixent de grups de recerca a la comunitat científica, degut especialment a les característiques intrínsiques dels mencionats sistemes i als beneficis que els peers podrien proporcionar a la reducció de la càrrega en el servidor. Aquest treball tracta l'anàlisi del rendiment d'un sistema P2P-VoD considerant el comportament d'usuaris obtingut amb traçes reals i amb patrons sintètics. Els experiments realitzats mostren que és viable assolir un rendiment proper al cas més óptim. Com treball futur es considerarà la monitorització de les característiques físiques de la xarxa per a poder millorar el disseny dels diferents aspectes que formen un sistema de VoD.El diseño arquitectónico y el despliegue de sistemas de Video bajo Demanda "Peer-to-Peer" que soportan funcionalidades VCR está captando el interés de un número creciente de grupos de investigación dentro de la comunidad científica; especialmente debido a las características intrínsecas de tales sistemas y a los beneficios que los peers podrían proporcionar en la reducción de la carga en el servidor. Este trabajo se enfoca en el análisis de rendimiento de un sistema P2PVoD considerando el comportamiento de usuarios obtenido de trazas reales, junto a otros patrones sintéticos. Los experimentos realizados muestran que es viable lograr un rendimiento cercano al caso más óptimo. El trabajo futuro considerará la monitorización de las características físicas de la red para poder mejorar el diseño de los diferentes aspectos que conforman un sistema de VoD

Proactive Mechanisms for Video-on-Demand Content Delivery

Video delivery over the Internet is the dominant source of network load all over the world. Especially VoD streaming services such as YouTube, Netflix, and Amazon Video have propelled the proliferation of VoD in many peoples' everyday life. VoD allows watching video from a large quantity of content at any time and on a multitude of devices, including smart TVs, laptops, and smartphones. Studies show that many people under the age of 32 grew up with VoD services and have never subscribed to a traditional cable TV service. This shift in video consumption behavior is continuing with an ever-growing number of users. satisfy this large demand, VoD service providers usually rely on CDN, which make VoD streaming scalable by operating a geographically distributed network of several hundreds of thousands of servers. Thereby, they deliver content from locations close to the users, which keeps traffic local and enables a fast playback start. CDN experience heavy utilization during the day and are usually reactive to the user demand, which is not optimal as it leads to expensive over-provisioning, to cope with traffic peaks, and overreacting content eviction that decreases the CDN's performance. However, to sustain future VoD streaming projections with hundreds of millions of users, new approaches are required to increase the content delivery efficiency. To this end, this thesis identifies three key research areas that have the potential to address the future demand for VoD content. Our first contribution is the design of vFetch, a privacy-preserving prefetching mechanism for mobile devices. It focuses explicitly on OTT VoD providers such as YouTube. vFetch learns the user interest towards different content channels and uses these insights to prefetch content on a user terminal. To do so, it continually monitors the user behavior and the device's mobile connectivity pattern, to allow for resource-efficient download scheduling. Thereby, vFetch illustrates how personalized prefetching can reduce the mobile data volume and alleviate mobile networks by offloading peak-hour traffic. Our second contribution focuses on proactive in-network caching. To this end, we present the design of the ProCache mechanism that divides the available cache storage concerning separate content categories. Thus, the available storage is allocated to these divisions based on their contribution to the overall cache efficiency. We propose a general work-flow that emphasizes multiple categories of a mixed content workload in addition to a work-flow tailored for music video content, the dominant traffic source on YouTube. Thereby, ProCache shows how content-awareness can contribute to efficient in-network caching. Our third contribution targets the application of multicast for VoD scenarios. Many users request popular VoD content with only small differences in their playback start time which offers a potential for multicast. Therefore, we present the design of the VoDCast mechanism that leverages this potential to multicast parts of popular VoD content. Thereby, VoDCast illustrates how ISP can collaborate with CDN to coordinate on content that should be delivered by ISP-internal multicast