2 research outputs found
Recommended from our members
Fast data replenishment in peer to peer networks
Peer-to-Peer (P2P) based distributed storage systems have gain much popularity in recent years. These systems rely greatly on the data redundancy to be robust under network dynamics, i.e., the dynamics of peer entering and departing the network. Hence, it is important to implement mechanisms for maintaining a certain level of data redundancy at all times in the network. One such mechanism is called distributed data replenishment which attempts to repair data due to a peer failure or departure in a distributed manner. Such distributed data replenishment schemes make use of the well-known Repetition code, the Reed Solomon code, or recently the Random Linear Network Coding techniques. However, these schemes do not consider bandwidth associated with peers during the replenishment. In this thesis we explore techniques for fast replenishment by taking into consideration the bandwidth capacities of peer links. Specifically, we formulate the problem of fast replenishment via linear programing framework. Our simulation results indicate that the proposed fast replenishment significantly outperforms the current approach under many typical network scenarios
Recommended from our members
Network coding for sensor networks, distributed storage and video streaming
The classical store-and-forward routing has and will continue to be the most important routing architecture in many modern packet-switched communication networks. In a packet-switched network, data is sent in the form of discrete packets that traverse hop-by-hop from a source to a destination. At each intermediate hop, the router stores and examines the packets it receives then forwards them to the next hop until they reach the correct destinations according to some pre-defined routing algorithms. Importantly, the intermediate routers do not modify but simply store and forward the contents of the packets. In contrast, a new generalized approach to routing called Network Coding (NC) allows the intermediate routers to modify and combine packets from different sources and destinations in such a way that increases the overall throughput. The core idea of NC allowing the intermediate nodes in a network to perform data processing has a wide range of applications well beyond its initial application to routing, impacting different disciplines from distributed data storage and security to energy efficient sensor networks and Internet media streaming. To that end, this dissertation aims to develop the theories and applications of NC via four main thrusts:
1) Energy efficient NC techniques for sensor networks,
2) Novel NC techniques and protocols for Internet video streaming,
3) Stochastic data replenishment for large scale NC-based distributed storage
systems,
4) Real-world implementation of NC-based distributed video streaming system.
In thrust one, we describe a novel cross-sensor coding technique that combines
network topology and coding techniques to maximize the life-time of a sensor network,
by addressing the uneven energy consumption problem in data gathering
sensor networks where the nodes closer to the sink tend to consume more energy
than those of the farther nodes. Our approach is based on the following observation
from the sensor networks using On-Off Keying and digital transmission:
transmitting bit "1" consumes much more energy than bit "0". Our proposed
coding technique exploits this difference to reduce the communication energy by
limiting the number of bits "1" in the output codeword (low-weight codeword) and
to use NC-based cross-sensor coding technique to equalize the communication energy
among the nodes. This cross-sensor coding scheme can significantly extend
the network lifetime as compared with traditional (binary) coding by solving the
energy-consumption unfairness problem. The theoretical and experimental results
confirm that transmission energy can be reduced substantially (e.g., a factor of 15)
and the unequal energy consumption among nodes can be practically eliminated.
In thrust two, we describe a rate distortion aware hierarchical NC technique
and transport protocol for Internet video streaming. We begin by proposing
a NC-based multi-sender streaming framework that reduces the overall storage,
eliminates the complexity of sender synchronization, and enables TCP streaming.
Furthermore, we propose a Hierarchical Network Coding (HNC) technique that
facilitates scalable video streaming to combat bandwidth fluctuation on the Internet.
This HNC technique enables receiver to recover the important data gracefully
in the presence of limited bandwidth which causes an increase in decoding delay.
Simulations demonstrate that under certain scenarios, our proposed NC techniques
can result in bandwidth saving up to 60% over the traditional schemes.
In thrust three, we present a theory of NC-based data replenishment to automate
the process of data maintenance for large scale distributed storage systems.
The data replenishment mechanism is the core of these systems that promises to
reduce the coordination complexity and increases performance scalability. The
data replenishment automates the process of maintaining a sufficient level of data
redundancy to ensure the availability of data in presence of peer departures and
failures. The dynamics of peers entering and leaving the network is modeled as
a stochastic process. We propose a novel analytical time-backward technique to
bound the expected time, the longer the better, for a piece of data to remain in
P2P systems. Both theoretical and simulation results are in agreement, indicating
that our proposed data replenishment via random linear network coding (RLNC)
outperforms other popular strategies that employ repetition and channel coding
techniques. Specifically, we show that the expected time for a piece of data to
remain in a P2P system is exponential in the number of peers used to store the
data for the RLNC-based strategy, while they are quadratic for other strategies.
Furthermore, the time-backward technique can be applied to problems in other
disciplines such as gene population modeling in theoretical biology.
Finally in thrust four, we present the architecture, design, and experimental
results of an actual NC-based distributed video streaming system. We first implement
random linear network coding (RLNC) library and show the feasibility of
using RLNC in P2P video streaming applications. Then we design, implement and
analyze RESnc - a resilient P2P video storage and streaming over the Internet using
network coding. RESnc increases the streaming throughput and data resiliency
against peer departures and failures using peer diversity. These improvements are
based on three architectural elements:
1) The RLNC scheme that breaks a video stream into multiple smaller pieces,
codes, and disperses them throughout peers in the network, in such a way to
maximize the probability of recovering the original video under peer departures
and failures;
2) The scalable mechanism for automating the data replenishment process using
RLNC to maintain a sufficient level of redundancy for video stored in the system;
3) The path-diversity streaming protocol for a client to simultaneously stream
a video from multiple peers with minimal coordination.
Experimental results demonstrated that our system adapts well with bandwidth
fluctuation, provides significant playback quality improvement and bandwidth saving