Network Coding for Speedup in Switches

We present a graph theoretic upper bound on speedup needed to achieve 100% throughput in a multicast switch using network coding. By bounding speedup, we show the equivalence between network coding and speedup in multicast switches - i.e. network coding, which is usually implemented using software, can in many cases substitute speedup, which is often achieved by adding extra switch fabrics. This bound is based on an approach to network coding problems called the "enhanced conflict graph". We show that the "imperfection ratio" of the enhanced conflict graph gives an upper bound on speedup. In particular, we apply this result to K-by-N switches with traffic patterns consisting of unicasts and broadcasts only to obtain an upper bound of min{(2K-1)/K, 2N/(N+1)}.Comment: 5 pages, 4 figures, IEEE ISIT 200

Achieving 100% throughput for multicast traffic in input-queued switches

A general approach of designing input-queued multicast switch is to employ multicast switch fabric, where packets can be replicated inside the switch fabric. As compared with unicast switch fabric, the achievable traffic rate region of a switch can be increased, but it is still less than the admissible traffic rate region. In other words, achieving 100% throughput for any admissible multicast traffic pattern is not possible. In this paper, we first revisit the fundamental problems faced by input-queued switch in supporting multicast traffic. We then argue that multicast switch fabric is not necessary if a load-balanced approach is followed. Accordingly, an existing load-balanced two-stage switch architecture [12], consisting of unicast switch fabrics, can be adopted to provide 100% throughput for any admissible multicast traffic pattern. Since the two-stage switch requires no speedup in both switch fabric and packet buffers, we consider it a two-stage input-queued switch. It can be seen that its implementation complexity is much lower than conventional (single-stage) input-queued multicast switches. As compared with the work in [12], our approach is more systematic and we propose a more effective load balancing mechanism. © 2011 IEEE.link_to_subscribed_fulltextProceedings of the IEEE Global Telecommunications Conference (GLOBECOM 2011), Houston, TX, USA, 5-9 December 201

Network Coding Applications

Network coding is an elegant and novel technique introduced at the turn of the millennium to improve network throughput and performance. It is expected to be a critical technology for networks of the future. This tutorial deals with wireless and content distribution networks, considered to be the most likely applications of network coding, and it also reviews emerging applications of network coding such as network monitoring and management. Multiple unicasts, security, networks with unreliable links, and quantum networks are also addressed. The preceding companion deals with theoretical foundations of network coding

Network coding for robust wireless networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 157-167).Wireless networks and communications promise to allow improved access to services and information, ubiquitous connectivity, and mobility. However, current wireless networks are not well-equipped to meet the high bandwidth and strict delay requirements of future applications. Wireless networks suffer from frequent losses and low throughput. We aim to provide designs for robust wireless networks. This dissertation presents protocols and algorithms that significantly improve wireless network performance and effectively overcome interference, erasures, and attacks. The key idea behind this dissertation is in understanding that wireless networks are fundamentally different from wired networks, and recognizing that directly applying techniques from wired networks to wireless networks limits performance. The key ingredient underlying our algorithms and protocols is network coding. By recognizing the algebraic nature of information, network coding breaks the convention of routing networks, and allows mixing of information in the intermediate nodes and routers. This mixing has been shown to have numerous performance benefits, e.g. increase in throughput and robustness against losses and failures. We present three protocols and algorithms, each using network coding to harness a different characteristic of the wireless medium. We address the problem of interference, erasures, and attacks in wireless networks with the following network coded designs. -- Algebraic NC exploits strategic interference to provide a distributed, randomized code construction for multi-user wireless networks. Network coding framework simplifies the multi-user wireless network model, and allows us to describe the multi-user wireless networks in an algebraic framework. This algebraic framework provides a randomized, distributed code construction, which we show achieves capacity for multicast connections as well as a certain set of non-multicast connections. -- TCP/NC efficiently and reliably delivers data over unreliable lossy wireless networks. TCP, which was designed for reliable transmission over wired networks, often experiences severe performance degradation in wireless networks. TCP/NC combines network coding's erasure correction capabilities with TCP's congestion control mechanism and reliability. We show that TCP/NC achieves significantly higher throughput than TCP in lossy networks; therefore, TCP/NC is well suited for reliable communication in lossy wireless networks. -- Algebraic Watchdog takes advantage of the broadcast nature of wireless networks to provide a secure global self-checking network. Algebraic Watchdog allows nodes to detect malicious behaviors probabilistically, and police their neighbors locally using overheard messages. Unlike traditional detection protocols which are receiver-based, this protocol gives the senders an active role in checking the nodes downstream. We provide a trellis-based inference algorithm and protocol for detection, and analyze its performance. The main contribution of this dissertation is in providing algorithms and designs for robust wireless networks using network coding. We present how network coding can be applied to overcome the challenges of operating in wireless networks. We present both analytical and simulation results to support that network coded designs, if designed with care, can bring forth significant gains, not only in terms of throughput but also in terms of reliability, security, and robustness.by MinJi Kim.Ph.D

Network Coding for Speedup in Switches

Abstract — We present a graph theoretic upper bound on speedup needed to achieve 100 % throughput in a multicast switch using network coding. By bounding speedup, we show the equivalence between network coding and speedup in multicast switches- i.e. network coding, which is usually implemented using software, can in many cases substitute speedup, which is often achieved by adding extra switch fabrics. This bound is based on an approach to network coding problems called the “enhanced conflict graph”. We show that the “imperfection ratio ” of the enhanced conflict graph gives an upper bound on speedup. In particular, we apply this result to K × N switches with traffic patterns consisting of unicasts and broadcasts only to obtain an upper bound of min ( 2K−