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492
Raptor codes
- 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: ..."
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Cited by 577 (7 self)
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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
LT Codes
, 2002
"... We introduce LT codes, the first rateless erasure codes that are very efficient as the data length grows. ..."
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Cited by 568 (2 self)
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We introduce LT codes, the first rateless erasure codes that are very efficient as the data length grows.
Small Byzantine Quorum Systems
- 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 ..."
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Cited by 468 (49 self)
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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
- 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 ..."
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Cited by 360 (3 self)
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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
, 2002
"... Overlay networks have emerged as a powerful and highly flexible method for delivering content. We study how to optimize through-put of large, multipoint transfers across richly connected overlay networks, focusing on the question of what to put in each transmit-ted packet. We first make the case for ..."
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Cited by 247 (8 self)
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Overlay networks have emerged as a powerful and highly flexible method for delivering content. We study how to optimize through-put of large, multipoint transfers across richly connected overlay networks, focusing on the question of what to put in each transmit-ted packet. We first make the case for transmitting encoded content in this scenario, arguing for the digital fountain approach which en-ables end-hosts to efficiently restitute the original content of size n from a subset of any n symbols from a large universe of encoded symbols. Such an approach affords reliability and a substantial de-gree of application-level flexibility, as it seamlessly tolerates packet loss, connection migration, and parallel transfers. However, since the sets of symbols acquired by peers are likely to overlap substan-tially, care must be taken to enable them to collaborate effectively. We provide a collection of useful algorithmic tools for efficient es-timation, summarization, and approximate reconciliation of sets of symbols between pairs of collaborating peers, all of which keep messaging complexity and computation to a minimum. Through simulations and experiments on a prototype implementation, we demonstrate the performance benefits of our informed content de-livery mechanisms and how they complement existing overlay net-work architectures.
Accessing multiple mirror sites in parallel: using tornado codes to speed up downloads
- IN INFOCOM ’99.EIGHTEENTH ANNUALJOINT CONFERENCE OFTHEIEEECOMPUTER ANDCOMMUNICATIONS SOCIETIES. PROCEEDINGS. IEEE,VOL.1,NEWYORK,NY,USA,MAR. 21–25,1999,PP.275–283
, 1999
"... 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 t ..."
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Cited by 185 (17 self)
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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.
Resilient Peer-to-Peer Streaming
- 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 ..."
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Cited by 182 (4 self)
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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
Analyzing and Improving a BitTorrent Network’s Performance Mechanisms
, 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 ..."
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Cited by 177 (0 self)
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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.
A Digital Fountain Approach to Asynchronous Reliable Multicast
- 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 ..."
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Cited by 174 (10 self)
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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.
PROMISE: Peer-to-Peer Media Streaming Using CollectCast
, 2003
"... We present the design, implementation, and evaluation of PROMISE, a novel peer-to-peer media streaming system encompassing the key functions of peer lookup, peer-based aggregated streaming, and dynamic adaptations to network and peer conditions. Particularly, PROMISE is based on a new application l ..."
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Cited by 172 (12 self)
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We present the design, implementation, and evaluation of PROMISE, a novel peer-to-peer media streaming system encompassing the key functions of peer lookup, peer-based aggregated streaming, and dynamic adaptations to network and peer conditions. Particularly, PROMISE is based on a new application level P2P service called CollectCast. CollectCast performs three main functions: (1) inferring and leveraging the underlying network topology and performance information for the selection of senders; (2) monitoring the status of peers and connections and reacting to peer/connection failure or degradation with low overhead; (3) dynamically switching active senders and standby senders, so that the collective network performance out of the active senders remains satisfactory. Based on both real-world measurement and simulation, we evaluate the performance of PROMISE, and discuss lessons learned from our experience with respect to the practicality and further optimization of PROMISE.
