In Distributed Algorithms, Nancy Lynch provides a blueprint for designing, implementing, and analyzing distributed algorithms. She directs her book at a wide audience, including students, programmers, system designers, and researchers.



Distributed Algorithms contains the most significant algorithms and impossibility results in the area, all in a simple automata-theoretic setting. The algorithms are proved correct, and their complexity is analyzed according to precisely defined complexity measures. The problems covered include resource allocation, communication, consensus among distributed processes, data consistency, deadlock detection, leader election, global snapshots, and many others.



The material is organized according to the system model-first by the timing model and then by the interprocess communication mechanism. The material on system models is isolated in separate chapters for easy reference.



The presentation is completely rigorous, yet is intuitive enough for immediate comprehension. This book familiarizes readers with important problems, algorithms, and impossibility results in the area: readers can then recognize the problems when they arise in practice, apply the algorithms to solve them, and use the impossibility results to determine whether problems are unsolvable. The book also provides readers with the basic mathematical tools for designing new algorithms and proving new impossibility results. In addition, it teaches readers how to reason carefully about distributed algorithms-to model them formally, devise precise specifications for their required behavior, prove their correctness, and evaluate their performance with realistic measures.


Table of Contents

1 Introduction 
2 Modelling I; Synchronous Network Model 
3 Leader Election in a Synchronous Ring 
4 Algorithms in General Synchronous Networks 
5 Distributed Consensus with Link Failures 
6 Distributed Consensus with Process Failures 
7 More Consensus Problems 
8 Modelling II: Asynchronous System Model 
9 Modelling III: Asynchronous Shared Memory Model 
10 Mutual Exclusion 
11 Resource Allocation 
12 Consensus 
13 Atomic Objects 
14 Modelling IV: Asynchronous Network Model 
15 Basic Asynchronous Network Algorithms 
16 Synchronizers 
17 Shared Memory versus Networks 
18 Logical Time 
19 Global Snapshots and Stable Properties 
20 Network Resource Allocation 
21 Asynchronous Networks with Process Failures 
22 Data Link Protocols 
23 Partially Synchronous System Models 
24 Mutual Exclusion with Partial Synchrony 
25 Consensus with Partial Synchrony

Distributed algorithms

Distributed operating systems have many aspects in common with centralized ones, but they also differ in certain ways This paper is intended as an introduction to distributed operating systems, and especially to current university research about them After a discussion of what constitutes a distributed operating system and how it is distinguished from a computer network, various key design issues are discussed Then several examples of current research projects are examined in some detail, namely, the Cambridge Distributed Computing System, Amoeba, V, and Eden

https://cds.cern.ch/record/400319/files/p101.pdf

Distributed Operating Systems

Busy-wait techniques are heavily used for mutual exclusion and barrier synchronization in shared-memory parallel programs. Unfortunately, typical implementations of busy-waiting tend to produce large amounts of memory and interconnect contention, introducing performance bottlenecks that become markedly more pronounced as applications scale. We argue that this problem is not fundamental, and that one can in fact construct busy-wait synchronization algorithms that induce no memory or interconnect contention. The key to these algorithms is for every processor to spin on separate locally-accessible flag variables, and for some other processor to terminate the spin with a single remote write operation at an appropriate time. Flag variables may be locally-accessible as a result of coherent caching, or by virtue of allocation in the local portion of physically distributed shared memory.We present a new scalable algorithm for spin locks that generates 0(1) remote references per lock acquisition, independent of the number of processors attempting to acquire the lock. Our algorithm provides reasonable latency in the absence of contention, requires only a constant amount of space per lock, and requires no hardware support other than a swap-with-memory instruction. We also present a new scalable barrier algorithm that generates 0(1) remote references per processor reaching the barrier, and observe that two previously-known barriers can likewise be cast in a form that spins only on locally-accessible flag variables. None of these barrier algorithms requires hardware support beyond the usual atomicity of memory reads and writes.We compare the performance of our scalable algorithms with other software approaches to busy-wait synchronization on both a Sequent Symmetry and a BBN Butterfly. Our principal conclusion is that contention due to synchronization need not be a problem in large-scale shared-memory multiprocessors. The existence of scalable algorithms greatly weakens the case for costly special-purpose hardware support for synchronization, and provides a case against so-called “dance hall” architectures, in which shared memory locations are equally far from all processors. —From the Authors' Abstract

/pdf/algorithms-for-scalable-synchronization-on-shared-memory-2fqah2bkze.pdf

Algorithms for scalable synchronization on shared-memory multiprocessors

One measure of the usefulness of a general-purpose distributed computing system is the system's ability to provide a level of performance commensurate to the degree of multiplicity of resources present in the system. A taxonomy of approaches to the resource management problem is presented in an attempt to provide a common terminology and classification mechanism necessary in addressing this problem. The taxonomy, while presented and discussed in terms of distributed scheduling, is also applicable to most types of resource management. >

/pdf/a-taxonomy-of-scheduling-in-general-purpose-distributed-2ar4ly9zfl.pdf

A taxonomy of scheduling in general-purpose distributed computing systems

An algorithm is proposed that creates mutual exclusion in a computer network whose nodes communicate only by messages and do not share memory. The algorithm sends only 2*(N - 1) messages, where N is the number of nodes in the network per critical section invocation. This number of messages is at a minimum if parallel, distributed, symmetric control is used; hence, the algorithm is optimal in this respect. The time needed to achieve mutual exclusion is also minimal under some general assumptions. As in Lamport's "bakery algorithm," unbounded sequence numbers are used to provide first-come firstserved priority into the critical section. It is shown that the number can be contained in a fixed amount of memory by storing it as the residue of a modulus. The number of messages required to implement the exclusion can be reduced by using sequential node-by-node processing, by using broadcast message techniques, or by sending information through timing channels. The "readers and writers" problem is solved by a simple modification of the algorithm and the modifications necessary to make the algorithm robust are described.

/pdf/an-optimal-algorithm-for-mutual-exclusion-in-computer-lq856cslpa.pdf

An optimal algorithm for mutual exclusion in computer networks

Given the highly empirical nature of research in cloud computing, networked systems, and related fields, testbeds play an important role in the research ecosystem. In this paper, we cover one such facility, CloudLab, which supports systems research by providing raw access to programmable hardware, enabling research at large scales, and creating a shared platform for repeatable research.

We present our experiences designing CloudLab and operating it for four years, serving nearly 4,000 users who have run over 79,000 experiments on 2,250 servers, switches, and other pieces of datacenter equipment. From this experience, we draw lessons organized around two themes. The first set comes from analysis of data regarding the use of CloudLab: how users interact with it, what they use it for, and the implications for facility design and operation. Our second set of lessons comes from looking at the ways that algorithms used "under the hood," such as resource allocation, have important-- and sometimes unexpected--effects on user experience and behavior. These lessons can be of value to the designers and operators of IaaS facilities in general, systems testbeds in particular, and users who have a stake in understanding how these systems are built.

/pdf/the-design-and-operation-of-cloudlab-52c7h9x9c7.pdf

The design and operation of cloudlab

A document processing system for accurately and efficiently analyzing documents and methods for making and using same. Each incoming document includes at least one section of textual content and is provided in an electronic form or as a paper-based document that is converted into an electronic form. Since many categories of documents, such as legal and accounting documents, often include one or more common text sections with similar textual content, the document processing system compares the documents to identify and classify the common text sections. The document comparison can be further enhanced by dividing the document into document segments and comparing the document segments; whereas, the conversion of paper-based documents likewise can be improved by comparing the resultant electronic document with a library of standard phrases, sentences, and paragraphs. The document processing system thereby enables an image of the document to be manipulated, as desired, to facilitate its review.

System and method for comparing and reviewing documents

A migration tool and methods for migrating computer personalization information from one computer to another when a network is not available, when a network is available but use of the network is undesirable for some reason, and/or when the computer which is the source of the data being migrated has limited or unknown resources to support conventional forms of data migration.

Migration of computer personalization information

Methods, devices, signals, and systems are provided in a message routing architecture which provides improved capabilities for integrating “digital” communication through email messages with “analog” communication through voice and/or fax or pager messages. Email can be addressed using nothing more than a standard telephone or fax number. If the registered owner of the telephone or fax number has a corresponding email address, then the invention converts the telephone or fax number to the email address for delivery and uses standard email delivery systems to deliver the message. If no conventional delivery email address is known, or if the message sender or recipient specify multiple delivery modes, then the email message content is transformed into voice, pager and/or fax content and delivered to the recipient using the telephone or fax number which was specified as the email address. Familiar telecommunications services such as call forwarding and selective call blocking can also be used with messages that originate as email. The invention also supports use of telecommunications numbers as indexes into databases which contain public key certificates, to make it unnecessary for a proposed message recipient to provide its public key expressly in advance to each particular proposed message originator.

Glenn Ricart

Papers

An optimal algorithm for mutual exclusion in computer networks

The design and operation of cloudlab

System and method for comparing and reviewing documents

Migration of computer personalization information

Message routing with telecommunication number addressing and key management