114 research outputs found
vSkyConf: Cloud-assisted Multi-party Mobile Video Conferencing
As an important application in the busy world today, mobile video
conferencing facilitates virtual face-to-face communication with friends,
families and colleagues, via their mobile devices on the move. However, how to
provision high-quality, multi-party video conferencing experiences over mobile
devices is still an open challenge. The fundamental reason behind is the lack
of computation and communication capacities on the mobile devices, to scale to
large conferencing sessions. In this paper, we present vSkyConf, a
cloud-assisted mobile video conferencing system to fundamentally improve the
quality and scale of multi-party mobile video conferencing. By novelly
employing a surrogate virtual machine in the cloud for each mobile user, we
allow fully scalable communication among the conference participants via their
surrogates, rather than directly. The surrogates exchange conferencing streams
among each other, transcode the streams to the most appropriate bit rates, and
buffer the streams for the most efficient delivery to the mobile recipients. A
fully decentralized, optimal algorithm is designed to decide the best paths of
streams and the most suitable surrogates for video transcoding along the paths,
such that the limited bandwidth is fully utilized to deliver streams of the
highest possible quality to the mobile recipients. We also carefully tailor a
buffering mechanism on each surrogate to cooperate with optimal stream
distribution. We have implemented vSkyConf based on Amazon EC2 and verified the
excellent performance of our design, as compared to the widely adopted unicast
solutions.Comment: 10 page
End-to-end security in active networks
Active network solutions have been proposed to many of the problems caused by the increasing heterogeneity of the Internet. These ystems allow nodes within the network to process data passing through in several ways. Allowing code from various sources to run on routers introduces numerous security concerns that have been addressed by research into safe languages, restricted execution environments, and other related areas. But little attention has been paid to an even more critical question: the effect on end-to-end security of active flow manipulation. This thesis first examines the threat model implicit in active networks. It develops a framework of security protocols in use at various layers of the networking stack, and their utility to multimedia transport and flow processing, and asks if it is reasonable to give active routers access to the plaintext of these flows. After considering the various security problem introduced, such as vulnerability to attacks on intermediaries or coercion, it concludes not. We then ask if active network systems can be built that maintain end-to-end security without seriously degrading the functionality they provide. We describe the design and analysis of three such protocols: a distributed packet filtering system that can be used to adjust multimedia bandwidth requirements and defend against denial-of-service attacks; an efficient composition of link and transport-layer reliability mechanisms that increases the performance of TCP over lossy wireless links; and a distributed watermarking servicethat can efficiently deliver media flows marked with the identity of their recipients. In all three cases, similar functionality is provided to designs that do not maintain end-to-end security. Finally, we reconsider traditional end-to-end arguments in both networking and security, and show that they have continuing importance for Internet design. Our watermarking work adds the concept of splitting trust throughout a network to that model; we suggest further applications of this idea
DecVi: Adaptive Video Conferencing on Open Peer-to-Peer Networks
Video conferencing has become the preferred way of interacting virtually.
Current video conferencing applications, like Zoom, Teams or WebEx, are
centralized, cloud-based platforms whose performance crucially depends on the
proximity of clients to their data centers. Clients from low-income countries
are particularly affected as most data centers from major cloud providers are
located in economically advanced nations. Centralized conferencing applications
also suffer from occasional outages and are embattled by serious privacy
violation allegations. In recent years, decentralized video conferencing
applications built over p2p networks and incentivized through blockchain are
becoming popular. A key characteristic of these networks is their openness:
anyone can host a media server on the network and gain reward for providing
service. Strong economic incentives combined with lower entry barrier to join
the network, makes increasing server coverage to even remote regions of the
world. These reasons, however, also lead to a security problem: a server may
obfuscate its true location in order to gain an unfair business advantage. In
this paper, we consider the problem of multicast tree construction for video
conferencing sessions in open p2p conferencing applications. We propose DecVi,
a decentralized multicast tree construction protocol that adaptively discovers
efficient tree structures based on an exploration-exploitation framework. DecVi
is motivated by the combinatorial multi-armed bandit problem and uses a
succinct learning model to compute effective actions. Despite operating in a
multi-agent setting with each server having only limited knowledge of the
global network and without cooperation among servers, experimentally we show
DecVi achieves similar quality-of-experience compared to a centralized globally
optimal algorithm while achieving higher reliability and flexibility
Distributed construction of resource-efficient overlay tree by approximating MST
Master'sMASTER OF SCIENC
Scaleable audio for collaborative environments
This thesis is concerned with supporting natural audio communication in collaborative environments across the Internet. Recent experience with Collaborative Virtual Environments, for example, to support large on-line communities and highly interactive social events, suggest that in the future there will be applications in which many users speak at the same time. Such applications will generate large and dynamically changing volumes of audio traffic that can cause congestion and hence packet loss in the network and so seriously impair audio quality. This thesis reveals that no current approach to audio distribution can combine support for large number of simultaneous speakers with TCP-fair responsiveness to congestion.
A model for audio distribution called Distributed Partial Mixing (DPM) is proposed that dynamically adapts both to varying numbers of active audio streams in collaborative environments and to congestion in the network. Each DPM component adaptively mixes subsets of its input audio streams into one or more mixed streams, which it then forwards to the other components along with any unmixed streams. DPM minimises the amount of mixing performed so that end users receive as many separate audio streams as possible within prevailing network resource constraints. This is important in order to allow maximum flexibility of audio presentation (especially spatialisation) to the end user. A distributed partial mixing prototype is realised as part of the audio service in MASSIVE-3. A series of experiments over a single network link demonstrate that DPM gracefully manages the tradeoff between preserving stable audio quality and being responsive to congestion and achieving fairness towards competing TCP traffic.
The problem of large scale deployment of DPM over heterogeneous networks is also addressed. The thesis proposes that a shared tree of DPM servers and clients, where the nodes of the tree can perform distributed partial mixing, is an effective basis for wide area deployment. Two models for realising this in two contrasting situations are then explored in more detail: a static, centralised, subscription-based DPM service suitable for fully managed networks, and a fully distributed self-organising DPM service suitable for unmanaged networks (such as the current Internet)
Service introduction in an active network
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 1999.Includes bibliographical references (p. 151-157).by David J. Wetherall.Ph.D
Scaleable audio for collaborative environments
This thesis is concerned with supporting natural audio communication in collaborative environments across the Internet. Recent experience with Collaborative Virtual Environments, for example, to support large on-line communities and highly interactive social events, suggest that in the future there will be applications in which many users speak at the same time. Such applications will generate large and dynamically changing volumes of audio traffic that can cause congestion and hence packet loss in the network and so seriously impair audio quality. This thesis reveals that no current approach to audio distribution can combine support for large number of simultaneous speakers with TCP-fair responsiveness to congestion.
A model for audio distribution called Distributed Partial Mixing (DPM) is proposed that dynamically adapts both to varying numbers of active audio streams in collaborative environments and to congestion in the network. Each DPM component adaptively mixes subsets of its input audio streams into one or more mixed streams, which it then forwards to the other components along with any unmixed streams. DPM minimises the amount of mixing performed so that end users receive as many separate audio streams as possible within prevailing network resource constraints. This is important in order to allow maximum flexibility of audio presentation (especially spatialisation) to the end user. A distributed partial mixing prototype is realised as part of the audio service in MASSIVE-3. A series of experiments over a single network link demonstrate that DPM gracefully manages the tradeoff between preserving stable audio quality and being responsive to congestion and achieving fairness towards competing TCP traffic.
The problem of large scale deployment of DPM over heterogeneous networks is also addressed. The thesis proposes that a shared tree of DPM servers and clients, where the nodes of the tree can perform distributed partial mixing, is an effective basis for wide area deployment. Two models for realising this in two contrasting situations are then explored in more detail: a static, centralised, subscription-based DPM service suitable for fully managed networks, and a fully distributed self-organising DPM service suitable for unmanaged networks (such as the current Internet)
Development of advanced multimedia services in P2P architectures
La transmissió de fluxos multimèdia en temps real (streaming) s’ha convertit en
un tema punter i de gran interès al món de la recerca d’Internet, especialment
quan ens referim a aplicacions de transmissió d’àudio i vídeo en directe a
través de xarxes peer-to-peer (P2P). Generalment, aquestes aplicacions han
de fer front a molts problemes en el seu disseny i implementació deguts a la
dinamicitat i heterogeneïtat que per natura caracteritzen les xarxes P2P. En
aquest projecte, s’introdueixen noves característiques que les aplicacions de
transmissió multimèdia P2P actuals no contemplen.
Els requisits de connexió i maquinari són diferents per a la transmissió de
fluxos de baixa i alta capacitat, no obstant, tots els nodes s’acostumen a
considerar idèntics, cosa que no representa una aproximació gaire encertada
tenint en compte un medi tan heterogeni. A més a més, amb la finalitat
d’aconseguir distinció entre nodes, es fa necessari la introducció d’un
mecanisme que permeti l’intercanvi de les capacitats específiques de cada
node, incloent-hi les de transcodificació de fluxos. Un altre aspecte a destacar
és el fet que aquestes aplicacions són difícils d’ampliar, incorporar nous
serveis o modificar les dades que porten precarregades com ara la llista de
canals de televisió disponibles, cosa que impossibilita garantir la disponibilitat
de la font tot el temps. Per altra banda, els serveis interactius tampoc s’han
desenvolupat gaire.
Aquest projecte proposa el disseny i implementació d’una plataforma de difusió
multimèdia P2P cooperativa i interactiva que permet superar els problemes
esmentats. La plataforma integra diferents mecanismes que permeten la
distribució en temps real de continguts multimèdia en diferents qualitats
incloent fluxos d’alta capacitat (com per exemple HD). Aquesta plataforma és
una solució novedosa basada en JXTA, DONET i ALM (Arbres Multicast a
nivell d’Aplicació) que proporciona un sistema ampliable segons noves
necessitats i facilita la inserció de nous serveis de valor afegit. La plataforma
proposada es fonamenta en la creació d’una arquitectura de 2 capes lògiques
superposades: una capa lògica JXTA, encarregada bàsicament de la
senyalització i intercanvi de metadades, i una capa de transmissió basada en
sockets UDP unicast. D’aquesta manera, la diferència entre la capa de
transmissió i la capa física es pot veure reduïda a partir de la informació
obtinguda de la capa JXTA, la qual es va actualitzant al llarg del temps
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