In this paper, we analyze the ability of several bounded-degree networks that are commonly used for parallel computation to tolerate faults. Among other things, we show that an N-node butterfly containing N 1\Gammaffl worst-case faults (for any constant ffl ? 0) can emulate a fault-free butterfly of the same size with only constant slowdown. Similar results are proved for the shuffleexchange graph. Hence, these networks become the first connected boundeddegree networks known to be able to sustain more than a constant number of worst-case faults without suffering more than a constant-factor slowdown in performance. We also show that an N-node butterfly whose nodes fail with some constant probability p can emulate a fault-free version of itself with a slowdown of 2 O(log N) , which is a very slowly increasing function of N . The proofs of these results combine the technique of redundant computation with new algorithms for (packet) routing around faults in hypercubic networks. Tech...

The proliferation of mobile computers and wireless networks requires the design of future distributed real-time applications to recognize and deal with the significant asymmetry between downstream and upstream communication capacities, and the significant disparitybetween server and client storage capacities.

This paper presents a simple local algorithm for load balancing in a distributed network. The algorithm makes no assumption about the structure of the network. It can be executed on a synchronous network with fixed topology, a synchronous network with dynamically changing topology, or an asynchronous network. It works quickly and balances well when the network has an expansion property. In particular, we show that in an n-node networkwith maximumdegree d whose live edges, at every time step, form a ¯-expander, the algorithm will balance the load to within an additive O(d log n=¯) term in O(\Delta log(n\Delta)=¯) time, where \Delta is the initial imbalance. The algorithm improves upon previous approaches that yield O(n) time bounds in dynamic and asynchronous networks. 1 Introduction One of the most fundamental problems to solve on a parallel computer or distributed network is to balance the load or work that must be performed among the various processors. This paper analyzes a sim...

The design of programs for broadcast disks which incorporate real-time and fault-tolerance requirements is considered. A generalized model for real-time fault-tolerant broadcast disks is defined. It is shown that designing programs for broadcast disks specified in this model is closely related to the scheduling of pinwheel task systems. Some new results in pinwheel scheduling theory are derived, which facilitate the efficient generation of realtime fault-tolerant broadcast disk programs.

We survey routing problems on fixed-connection networks. We consider many aspects of the routing problem and provide known theoretical results for various communication models. We focus on (partial) permutation, k-relation routing, routing to random destinations, dynamic routing, isotonic routing, fault tolerant routing, and related sorting results. We also provide a list of unsolved problems and numerous references.

We propose a new transport protocol, TCP Boston, that turns ATM's 53-byte cell-oriented switching architecture into an advantage for TCP/IP. At the core of TCP Boston is the Adaptive Information Dispersal Algorithm (AIDA), an efficient encoding technique that allows for dynamic redundancy control. AIDA makes TCP/IP's performance less sensitive to cell losses, thus ensuring a graceful degradation of TCP/IP's performance when faced with congested resources. In this paper, we introduce AIDA and overview the main features of TCP Boston. We present detailed simulation results that show the superiority of our protocol when compared to other adaptations of TCP/IP over ATMs. 1.

AIDA -- a novel elaboration on Michael O. Rabin's IDA [21] -- is a communication protocol that uses redundancy to achieve both timeliness and reliability. In AIDA redundancy is used to tackle several crucial problems. In particular, redundancy is used to tolerate failures, to increase the likelihood of meeting tight time-constraints, and to ration (based on task priorities) the limited bandwidth in the system. AIDA is a probabilistic protocol in the sense that it does not guarantee the fulfillment of hard time constraints. Instead, it guarantees a lower bound on the probability of fulfilling such constraints. Such a bound could be lowered so as to satisfy any level of confidence in the timeliness and reliability of the system. In this paper we present AIDA and contrast it with traditional communication scheduling techniques used in conjunction with time-critical applications in general, and distributed multimedia systems in particular. The suitability of AIDA-based bandwidth allocatio...

SomeCast is a novel paradigm for the reliable multicast of real-time data to a large set of receivers. SomeCast is receiver-initiated and thus scalable in the number of receivers, the diverse characteristics of paths between senders and receivers, and the dynamic conditions of such paths. SomeCast enables receivers to dynamically adjust the rate at which they receive multicast information to enable the satisfaction of their QoS constraints. This is done by enabling a receiver to join Some number of concurrent multiCast sessions, whereby each session delivers a portion of an encoding of the real-time data. By adjusting the number of such sessions dynamically, client-specic QoS constraints are met independently. The SomeCast paradigm can be thought of as a generalization of the AnyCast and ManyCast paradigms, which have been proposed in the literature to address issues of scalability of UniCast and MultiCast environments, respectively. In this paper we overview the SomeCast paradigm, de...

. Efficient data transfer between processors is an essential component in any large scale parallel computation. Motivated by the growing interest in parallel computers, a significant amount of theoretical research has been devoted to the area of interconnection networks for parallel computers, most of it to the packet routing (or store-and-forward) model of communication. We survey some of the major developments in this field, and discuss several new alternative models of communication, such as wormhole routing, virtual cut-through routing, and hot-potato routing. 1 Introduction Information exchange between processors is essential for any efficient parallel or distributed computation. In many large scale applications, communication time dominates the execution time of the whole parallel computation. Thus, the performance of a large scale parallel computer is highly correlated with the efficiency of its communication network and communication algorithm. Indeed, most parallel ma...