Classifying peer-to-peer network coding schemes

Abstract

Modern peer-to-peer file sharing systems distribute large files among peers using block partitioning. Blocks can be redistributed by a peer even before the whole file is available which highly decreases the distribution time. All peer-topeer networks face the problem of dynamic participation of the peers and dynamic bandwidth in the network. A leaving peer can cause an unrecoverable loss of blocks and obstruct further downloads of the file. Furthermore, the choice which block needs to be sent to which peer is a hard question. A random choice leads to the coupon collector problem which decreases the transmission rate. Filesharing networks like BitTorrent or Splitstream face such problems.Network Coding overcomes this problem by using error redundant codes of all blocks of the file. An efficient randomized variant of it, Practical Network Coding, transmits and recombines random linear combinations of the blocks of the partitioned file. As soon as enough linear combinations have been gathered, the original file can be decoded by a matrix operation, optimizing the network flow in any peer-to-peer network.All known Network Coding schemes, however, suffer from a quadratic cost of read/write disk operations for both encoding and decoding. Since there is an increasing gap between the speed of mass storage devices and the main memory, this poses an obstacle to a wider use of Network Coding schemes.In this paper we present and investigate new network coding schemes, which form a compromise between Network Coding and uncoded block transfer schemes like BitTorrent. These schemes, called Paircoding and Treecoding have smaller read/write costs for encoding and decoding than Practical Network Coding and higher throughput than BitTorrent.We develop a new framework for comparing the throughput of data (performance) of such peer-to-peer file sharing systems and classify these systems, as well as a BitTorrent variant which uses forward error correction. The dynamPermission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. ics of peer-to-peer networks are described by a round model where the set of participating peers and their link quality changes after each round. The framework compares two schemes for all possible dynamic scenarios. If the transmission rate of scheme A is at least as well as scheme B, then we say A performs as well as B. If this is the case and there is a scenario where A is better than B, we say A outperforms B. We show that all of our proposed coding schemes outperform BitTorrent, while being outperformed by Network Coding.This leads to a hierarchy, where BitTorrent is the worst performer and Network Coding is the best performer regarding throughput. Regardin...

Survey of Network Coding Based P2P File Sharing in Large Scale Networks

“…The proposed approach depends on computing the importance of the encoded pieces according to their underlying original pieces: those encoded pieces that consist of the original pieces that are less distributed among neighbors will be assigned with a higher priority to be requested. In contrast to [60], the authors claim that fixed Paircoding could promote the availability and diversity of the pieces. To evaluate the performance, the proposed approach is tested and compared against: (1) BitTorrent, (2) adaptive neighbor selection BitTorrent [19], and (3) BitTorrent using FEC [43].…”

Survey of Network Coding Based P2P File Sharing in Large Scale Networks

“…The proposed approach depends on computing the importance of the encoded pieces according to their underlying original pieces: those encoded pieces, that consist of the original pieces that are less distributed among neighbors, will be assigned with a higher priority to be requested. In contrast to [60], the authors claim that fixed Paircoding could promote the availability and diversity of the pieces. To evaluate the performane, the proposed approach is tested and compared against : (1) BitTorrent , (2) adaptive neighbor selection BitTorrent [19], and (3) BitTorrent using FEC [43].…”

Tree network coding for peer-to-peer networks

“…It is well known that a Vandermonde matrix fulfills this property. The following theorem solves the open problem stated in [10], where for the complexity of Tree Coding a bound of O(n) for the case k = 1 has been shown. Here, we show that every strategy which relies on Tree Coding with small number of trees can be performed efficiently.…”

“…Furthermore, we have introduced Tree Coding [10]. It outperforms a special version of Pair Coding called Fixed Pair Coding, while its relationship to Pair Coding is unknown.…”

“…Code blocks in Tree Coding, which was already introduced in [10], are defined by a complete binary tree. The leaves of this tree form the original file blocks multiplied by a coefficient.…”