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LT Codes

by Michael Luby , 2002
"... We introduce LT codes, the first rateless erasure codes that are very efficient as the data length grows. ..."
Abstract - Cited by 567 (2 self) - Add to MetaCart
We introduce LT codes, the first rateless erasure codes that are very efficient as the data length grows.
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Raptor codes

by Amin Shokrollahi - IEEE Transactions on Information Theory , 2006
"... LT-Codes are a new class of codes introduced in [1] for the purpose of scalable and fault-tolerant distribution of data over computer networks. In this paper we introduce Raptor Codes, an extension of LT-Codes with linear time encoding and decoding. We will exhibit a class of universal Raptor codes: ..."
Abstract - Cited by 567 (6 self) - Add to MetaCart
LT-Codes are a new class of codes introduced in [1] for the purpose of scalable and fault-tolerant distribution of data over computer networks. In this paper we introduce Raptor Codes, an extension of LT-Codes with linear time encoding and decoding. We will exhibit a class of universal Raptor codes: for a given integer k, and any real ε> 0, Raptor codes in this class produce a potentially infinite stream of symbols such that any subset of symbols of size k(1 + ε) is sufficient to recover the original k symbols with high probability. Each output symbol is generated using O(log(1/ε)) operations, and the original symbols are recovered from the collected ones with O(k log(1/ε)) operations. We will also introduce novel techniques for the analysis of the error probability of the decoder for finite length Raptor codes. Moreover, we will introduce and analyze systematic versions of Raptor codes, i.e., versions in which the first output elements of the coding system coincide with the original k elements. 1
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Small Byzantine Quorum Systems

by Jean-Philippe Martin, Lorenzo Alvisi, Michael Dahlin - DISTRIBUTED COMPUTING , 2001
"... In this paper we present two protocols for asynchronous Byzantine Quorum Systems (BQS) built on top of reliable channels---one for self-verifying data and the other for any data. Our protocols tolerate Byzantine failures with fewer servers than existing solutions by eliminating nonessential work in ..."
Abstract - Cited by 483 (49 self) - Add to MetaCart
In this paper we present two protocols for asynchronous Byzantine Quorum Systems (BQS) built on top of reliable channels---one for self-verifying data and the other for any data. Our protocols tolerate Byzantine failures with fewer servers than existing solutions by eliminating nonessential work in the write protocol and by using read and write quorums of different sizes. Since engineering a reliable network layer on an unreliable network is difficult, two other possibilities must be explored. The first is to strengthen the model by allowing synchronous networks that use time-outs to identify failed links or machines. We consider running synchronous and asynchronous Byzantine Quorum protocols over synchronous networks and conclude that, surprisingly, "self-timing" asynchronous Byzantine protocols may offer significant advantages for many synchronous networks when network time-outs are long. We show how to extend an existing Byzantine Quorum protocol to eliminate its dependency on reliable networking and to handle message loss and retransmission explicitly.

On-demand Multipath Distance Vector Routing in Ad Hoc Networks

by Mahesh K. Marina, Samir R. Das - in Proceedings of IEEE International Conference on Network Protocols (ICNP , 2001
"... We develop an on-demand, multipath distance vector protocol for mobile ad hoc networks. Specifically, we propose multipath extensions to a well-studied single path routing protocol known as Ad hoc On-demand Distance Vector (AODV). The resulting protocol is referred to as Ad hoc Ondemand Multipath Di ..."
Abstract - Cited by 342 (3 self) - Add to MetaCart
We develop an on-demand, multipath distance vector protocol for mobile ad hoc networks. Specifically, we propose multipath extensions to a well-studied single path routing protocol known as Ad hoc On-demand Distance Vector (AODV). The resulting protocol is referred to as Ad hoc Ondemand Multipath Distance Vector (AOMDV). The protocol computes multiple loop-free and link-disjoint paths. Loopfreedom is guaranteed by using a notion of "advertised hopcount." Link-disjointness of multiple paths is achieved by using a particular property of flooding. Performance comparison of AOMDV with AODV using ns-2 simulations shows that AOMDV is able to achieve a remarkable improvement in the end-to-end delay --- often more than a factor of two, and is also able to reduce routing overheads by about 20%. 1

Informed content delivery across adaptive overlay networks

by John W. Byers, Jeffrey Considine, Michael Mitzenmacher, Stanislav Rost - In Proceedings of ACM SIGCOMM , 2002
"... Abstract—Overlay networks have emerged as a powerful and highly flexible method for delivering content. We study how to optimize throughput of large transfers across richly connected, adaptive overlay networks, focusing on the potential of collaborative transfers between peers to supplement ongoing ..."
Abstract - Cited by 251 (9 self) - Add to MetaCart
Abstract—Overlay networks have emerged as a powerful and highly flexible method for delivering content. We study how to optimize throughput of large transfers across richly connected, adaptive overlay networks, focusing on the potential of collaborative transfers between peers to supplement ongoing downloads. First, we make the case for an erasure-resilient encoding of the content. Using the digital fountain encoding approach, end hosts can efficiently reconstruct the original content of size from a subset of any symbols drawn from a large universe of encoding symbols. Such an approach affords reliability and a substantial degree of application-level flexibility, as it seamlessly accommodates connection migration and parallel transfers while providing resilience to packet loss. However, since the sets of encoding symbols acquired by peers during downloads may overlap substantially, care must be taken to enable them to collaborate effectively. Our main contribution is a collection of useful algorithmic tools for efficient summarization and approximate reconciliation of sets of symbols between pairs of collaborating peers, all of which keep message complexity and computation to a minimum. Through simulations and experiments on a prototype implementation, we demonstrate the performance benefits of our informed content-delivery mechanisms and how they complement existing overlay network architectures. Index Terms—Bloom filter, content delivery, digital fountain, erasure code, min-wise sketch, overlay, peer-to-peer, reconciliation. I.
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Accessing multiple mirror sites in parallel: using tornado codes tospeed up downloads

by John W. Byers, Michael Luby, Michael Mitzenmacher - in INFOCOM ’99.Eighteenth AnnualJoint Conference oftheIEEEComputer andCommunications Societies. Proceedings. IEEE,vol.1,NewYork,NY,USA,Mar. 21–25,1999,pp.275–283
"... Abstracr- Mirror sites enable client requests to be serviced by any of a number of servers, reducing load at individual servers and dispersing network load. Typically, a client requests service from a single mirror site. We consider enabling a client to access a file from multiple mirror sites in pa ..."
Abstract - Cited by 187 (19 self) - Add to MetaCart
Abstracr- Mirror sites enable client requests to be serviced by any of a number of servers, reducing load at individual servers and dispersing network load. Typically, a client requests service from a single mirror site. We consider enabling a client to access a file from multiple mirror sites in parallel to speed up the download. To eliminate complex client-server negotiations that a straightforward implementation of this approach would require, we develop a feedback-free protocol based on erasure codes. We demonstrate that a protocol using fast Tornado codes can deliver dramatic speedups at the expense of transmitting a moderate number of additional packets into the network. Our scalable solution extends naturally to allow multiple clients to access data from multiple mirror sites simultaneously. Our approach applies naturally to wireless networks and satellite networks as well. I.

Resilient Peer-to-Peer Streaming

by Venkata N. Padmanabhan, Helen J. Wang, Philip A. Chou - IN PROC. OF IEEE ICNP , 2003
"... We consider the problem of distributing "five" streaming media content to a potentially large and highly dynamic population of hosts. Peer-to-peer content distribution is attractive in this setting because the bandwidth available to serve content scales with demand. A key challenge, howeve ..."
Abstract - Cited by 180 (5 self) - Add to MetaCart
We consider the problem of distributing "five" streaming media content to a potentially large and highly dynamic population of hosts. Peer-to-peer content distribution is attractive in this setting because the bandwidth available to serve content scales with demand. A key challenge, however, is making content distribution robust to peer transience. Our approach to providing robustness is to introduce redundancy, both in network paths and in data. We use multiple, diverse distribution trees to provide redundancy in network paths and multiple description coding (MDC) to provide redundancy in data. We present
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Analyzing and Improving a BitTorrent Network’s Performance Mechanisms

by Ashwin R. Bharambe, Cormac Herley, Venkata N. Padmanabhan , 2006
"... Abstract — In recent years, BitTorrent has emerged as a very scalable peer-to-peer file distribution mechanism. While early measurement and analytical studies have verified BitTorrent’s performance, they have also raised questions about various metrics (upload utilization, fairness, etc.), particula ..."
Abstract - Cited by 179 (0 self) - Add to MetaCart
Abstract — In recent years, BitTorrent has emerged as a very scalable peer-to-peer file distribution mechanism. While early measurement and analytical studies have verified BitTorrent’s performance, they have also raised questions about various metrics (upload utilization, fairness, etc.), particularly in settings other than those measured. In this paper, we present a simulationbased study of BitTorrent. Our goal is to deconstruct the system and evaluate the impact of its core mechanisms, both individually and in combination, on overall system performance under a variety of workloads. Our evaluation focuses on several important metrics, including peer link utilization, file download time, and fairness amongst peers in terms of volume of content served. Our results confirm that BitTorrent performs near-optimally in terms of uplink bandwidth utilization, and download time except under certain extreme conditions. We also show that low bandwidth peers can download more than they upload to the network when high bandwidth peers are present. We find that the rate-based tit-for-tat policy is not effective in preventing unfairness. We show how simple changes to the tracker and a stricter, block-based tit-for-tat policy, greatly improves fairness. I.
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A Digital Fountain Approach to Asynchronous Reliable Multicast

by John W. Byers, Michael Luby, Michael Mitzenmacher - IEEE Journal on Selected Areas in Communications , 2002
"... Abstract—The proliferation of applications that must reliably distribute large, rich content to a vast number of autonomous receivers motivates the design of new multicast and broadcast protocols. We describe an ideal, fully scalable protocol for these applications that we call a digital fountain. A ..."
Abstract - Cited by 175 (10 self) - Add to MetaCart
Abstract—The proliferation of applications that must reliably distribute large, rich content to a vast number of autonomous receivers motivates the design of new multicast and broadcast protocols. We describe an ideal, fully scalable protocol for these applications that we call a digital fountain. A digital fountain allows any number of heterogeneous receivers to acquire content with optimal efficiency at times of their choosing. Moreover, no feedback channels are needed to ensure reliable delivery, even in the face of high loss rates. We develop a protocol that closely approximates a digital fountain using two new classes of erasure codes that for large block sizes are orders of magnitude faster than standard erasure codes. We provide performance measurements that demonstrate the feasibility of our approach and discuss the design, implementation, and performance of an experimental system. Index Terms—Content delivery, erasure codes, forward error correction, reliable multicast, scalability. I.
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Novel Architectures for P2P Applications: the Continuous-Discrete Approach

by Moni Naor, Udi Wieder - ACM TRANSACTIONS ON ALGORITHMS , 2007
"... We propose a new approach for constructing P2P networks based on a dynamic decomposition of a continuous space into cells corresponding to processors. We demonstrate the power of these design rules by suggesting two new architectures, one for DHT (Distributed Hash Table) and the other for dynamic ex ..."
Abstract - Cited by 171 (8 self) - Add to MetaCart
We propose a new approach for constructing P2P networks based on a dynamic decomposition of a continuous space into cells corresponding to processors. We demonstrate the power of these design rules by suggesting two new architectures, one for DHT (Distributed Hash Table) and the other for dynamic expander networks. The DHT network, which we call Distance Halving, allows logarithmic routing and load, while preserving constant degrees. Our second construction builds a network that is guaranteed to be an expander. The resulting topologies are simple to maintain and implement. Their simplicity makes it easy to modify and add protocols. We show it is possible to reduce the dilation and the load of the DHT with a small increase of the degree. We present a provably good protocol for relieving hot spots and a construction with high fault tolerance. Finally we show that, using our approach, it is possible to construct any family of constant degree graphs in a dynamic environment, though with worst parameters. Therefore we expect that more distributed data structures could be designed and implemented in a dynamic environment.
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