725 research outputs found
Heterogeneity in Distributed Live Streaming: Blessing or Curse?
Distributed live streaming has brought a lot of interest in the past few
years. In the homogeneous case (all nodes having the same capacity), many
algorithms have been proposed, which have been proven almost optimal or
optimal. On the other hand, the performance of heterogeneous systems is not
completely understood yet. In this paper, we investigate the impact of
heterogeneity on the achievable delay of chunk-based live streaming systems. We
propose several models for taking the atomicity of a chunk into account. For
all these models, when considering the transmission of a single chunk,
heterogeneity is indeed a ``blessing'', in the sense that the achievable delay
is always faster than an equivalent homogeneous system. But for a stream of
chunks, we show that it can be a ``curse'': there is systems where the
achievable delay can be arbitrary greater compared to equivalent homogeneous
systems. However, if the system is slightly bandwidth-overprovisioned, optimal
single chunk diffusion schemes can be adapted to a stream of chunks, leading to
near-optimal, faster than homogeneous systems, heterogeneous live streaming
systems
Achieving the Optimal Steaming Capacity and Delay Using Random Regular Digraphs in P2P Networks
In earlier work, we showed that it is possible to achieve
streaming delay with high probability in a peer-to-peer network, where each
peer has as little as four neighbors, while achieving any arbitrary fraction of
the maximum possible streaming rate. However, the constant in the
delay term becomes rather large as we get closer to the maximum streaming rate.
In this paper, we design an alternative pairing and chunk dissemination
algorithm that allows us to transmit at the maximum streaming rate while
ensuring that all, but a negligible fraction of the peers, receive the data
stream with delay with high probability. The result is established
by examining the properties of graph formed by the union of two or more random
1-regular digraphs, i.e., directed graphs in which each node has an incoming
and an outgoing node degree both equal to one
AngelCast: cloud-based peer-assisted live streaming using optimized multi-tree construction
Increasingly, commercial content providers (CPs) offer streaming solutions using peer-to-peer (P2P) architectures, which promises significant scalabil- ity by leveraging clientsâ upstream capacity. A major limitation of P2P live streaming is that playout rates are constrained by clientsâ upstream capac- ities â typically much lower than downstream capacities â which limit the quality of the delivered stream. To leverage P2P architectures without sacri- ficing quality, CPs must commit additional resources to complement clientsâ resources. In this work, we propose a cloud-based service AngelCast that enables CPs to complement P2P streaming. By subscribing to AngelCast, a CP is able to deploy extra resources (angel), on-demand from the cloud, to maintain a desirable stream quality. Angels do not download the whole stream, nor are they in possession of it. Rather, angels only relay the minimal fraction of the stream necessary to achieve the desired quality. We provide a lower bound on the minimum angel capacity needed to maintain a desired client bit-rate, and develop a fluid model construction to achieve it. Realizing the limitations of the fluid model construction, we design a practical multi- tree construction that captures the spirit of the optimal construction, and avoids its limitations. We present a prototype implementation of AngelCast, along with experimental results confirming the feasibility of our service.Supported in part by NSF awards #0720604, #0735974, #0820138, #0952145, #1012798 #1012798 #1430145 #1414119. (0720604 - NSF; 0735974 - NSF; 0820138 - NSF; 0952145 - NSF; 1012798 - NSF; 1430145 - NSF; 1414119 - NSF
Peer-to-peer multimedia communication
I sistemi Peer-to-Peer (P2P) sono stati inventi, messi in campo e studiati da piĂš di
dieci anni, andando al di lĂ della semplice applicazione per scambio di file. Nelle reti P2P i partecipanti
si organizzano in una rete "overlay" che è astratta rispetto alle caratteristiche della sottostante rete fisica.
Scopo di questi sistemi è la distribuzione di risorse quali contenuti, spazio di memorizzazione o cicli macchina. Gli utenti quindi giocano un ruolo attivo e possono essere considerati come sia clienti che serventi allo stesso tempo per il particolare servizio che la rete P2P offre.
Lo scopo di questa tesi di dottorato è lo studio di questi sistemi ed il dare un contributo nella loro analisi
prestazionale. L'analisi mira a valutare le prestazioni raggiunte dai sistemi e/o i limiti teorici raggiungibili.
Infatti, nonostante esistano diversi meccanismi per il peer-to-peer streaming, l'analisi prestazionale di questo tipo di sistemi può essere considerata ancora nella sua infanzia. A questo scopo, i contributi principali di questa tesi di dottorato sono: i)la derivazione di un limite teorico per il ritardo nei sistemi di
P2P streaming, ii) la creazione di un algoritmo che sfrutti le conoscenze acquisite attraverso il lavoro teorico, iii) l'analisi prestazionale dell'algoritmo utilizzando un simulatore espressamente progettato per riprodurre le caratteristiche delle reti P2P reali composte da centinaia di migliaia di nodi che si connettono e disconnettono in continuazione.Peer-to-Peer (P2P) systems have been invented, deployed and researched for more
than ten years and went far beyond the simple ďŹle sharing applications. In P2P
networks, participants organize themselves in an overlay network that abstracts
from the topological characteristics of the underlying physical network. Aim of
these systems is the distribution of some kind of resources like contents, storage, or
CPU cycles. Users, therefore, play an active role so that they can be considered
as client and server at the same time, for the particular service that is provided
through the P2P paradigm.
Goal of this dissertation thesis is to study
these systems, and give contributes in their performance evaluation. The analysis
will aim to evaluate the achieved performance of a system and/or the performance
bounds that could be achievable.
In fact, even if there are several proposals of diďŹerent systems, peer-to-peer
streaming performance analysis can be considered still in its infancy and there is
still a lot of work to do. To this aim, the main contributes of this dissertation thesis
are i) the derivation of a theoretical delay bounds for P2P streaming system ii)
II
the creation of an algorithm that exploits the new insights that come out from the
theoretical study iii) the performance evaluation of this algorithm using an ad-hoc
simulator, expressly tailored to reproduce the characteristics of the real-world P2P
streaming systems, composed by hundred thousands of intermittently connected
users
Stochastic Analysis of Self-Sustainability in Peer-Assisted VoDSystems
AbstractâWe consider a peer-assisted Video-on-demand system, in which video distribution is supported both by peers caching the whole video and by peers concurrently downloading it. We propose a stochastic fluid framework that allows to characterize the additional bandwidth requested from the servers to satisfy all users watching a given video. We obtain analytical upper bounds to the server bandwidth needed in the case in which users download the video content sequentially. We also present a methodology to obtain exact solutions for special cases of peer upload bandwidth distribution. Our bounds permit to tightly characterize the performance of peer-assisted VoD systems as the number of users increases, for both sequential and nonsequential delivery schemes. In particular, we rigorously prove that the simple sequential scheme is asymptotically optimal both in the bandwidth surplus and in the bandwidth deficit mode, and that peer-assisted systems become totally self-sustaining in the surplus mode as the number of users grows large. I
Extended Equal Service and Differentiated Service Models for Peer-to-Peer File Sharing
Peer-to-Peer (P2P) systems have proved to be the most effective and popular
file sharing applications in recent years. Previous studies mainly focus on the
equal service and the differentiated service strategies when peers have no
initial data before their download. In an upload-constrained P2P file sharing
system, we model both the equal service process and the differentiated service
process when peers' initial data distribution satisfies some special
conditions, and also show how to minimize the time to get the file to any
number of peers. The proposed models can reveal the intrinsic relations among
the initial data amount, the size of peer set and the minimum last finish time.
By using the models, we can also provide arbitrary degree of differentiated
service to a certain number of peers. We believe that our analysis process and
achieved theoretical results could provide fundamental insights into studies on
bandwidth allocation and data scheduling, and can give helpful reference both
for improving system performance and building effective incentive mechanism in
P2P file sharing systems
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