Raft is a consensus algorithm for managing a replicated log. It produces a result equivalent to (multi-)Paxos, and it is as efficient as Paxos, but its structure is different from Paxos; this makes Raft more understandable than Paxos and also provides a better foundation for building practical systems. In order to enhance understandability, Raft separates the key elements of consensus, such as leader election, log replication, and safety, and it enforces a stronger degree of coherency to reduce the number of states that must be considered. Results from a user study demonstrate that Raft is easier for students to learn than Paxos. Raft also includes a new mechanism for changing the cluster membership, which uses overlapping majorities to guarantee safety.

/pdf/in-search-of-an-understandable-consensus-algorithm-2tvnovxuiu.pdf

In search of an understandable consensus algorithm

http://www.eis.mdx.ac.uk/staffpages/juanaugusto/CookAJ2009.pdf

Review: Ambient intelligence: Technologies, applications, and opportunities

The surprising success of cryptocurrencies has led to a surge of interest in deploying large scale, highly robust, Byzantine fault tolerant (BFT) protocols for mission-critical applications, such as financial transactions. Although the conventional wisdom is to build atop a (weakly) synchronous protocol such as PBFT (or a variation thereof), such protocols rely critically on network timing assumptions, and only guarantee liveness when the network behaves as expected. We argue these protocols are ill-suited for this deployment scenario. We present an alternative, HoneyBadgerBFT, the first practical asynchronous BFT protocol, which guarantees liveness without making any timing assumptions. We base our solution on a novel atomic broadcast protocol that achieves optimal asymptotic efficiency. We present an implementation and experimental results to show our system can achieve throughput of tens of thousands of transactions per second, and scales to over a hundred nodes on a wide area network. We even conduct BFT experiments over Tor, without needing to tune any parameters. Unlike the alternatives, HoneyBadgerBFT simply does not care about the underlying network.

/pdf/the-honey-badger-of-bft-protocols-3071umjz65.pdf

The Honey Badger of BFT Protocols

How smart are our environments? An updated look at the state of the art

http://henricksen.id.au/publications/PMC05.pdf

Developing context-aware pervasive computing applications: Models and approach

We present a protocol for general state machine replication - a method that provides strong consistency - that has high performance in a wide-area network. In particular, our protocol Mencius has high throughput under high client load and low latency under low client load even under changing wide-area network environment and client load. We develop our protocol as a derivation from the well-known protocol Paxos. Such a development can be changed or further refined to take advantage of specific network or application requirements.

/pdf/mencius-building-efficient-replicated-state-machines-for-unuok7kw9n.pdf

Mencius: building efficient replicated state machines for WANs

The smart classroom integrates voice-recognition, computer-vision, and other technologies to provide a tele-education experience similar to a real classroom experience.

The smart classroom: merging technologies for seamless tele-education

A software infrastructure is fundamental to a Smart Space. Previously proposed software infrastructures for Smart Space (SISS) did not sufficiently address the issue of performance and usability. A new solution, Smart Platform, which is focused on improving these aspects of a SISS, is presented in this paper. To optimize its intermodule communication performance, the stream-oriented communication is distinguished from the message-oriented ones, and a corresponding hybrid communication scheme is proposed. To improve the usability, a featured loose coupling structure, a straightforward Publish-and-Subscribe coordination model as well as a set of user-friendly deployment and development tools are developed. Besides, Smart Platform is intended as an open and generic SISS available for other research groups. To this end, XML-based message syntax and the open wire-protocol based architecture are adopted to make sharing research efforts more easily.

Smart Platform - a software infrastructure for Smart Space (SISS)

Classic Paxos and Fast Paxos are two protocols that are the core of efficient implementations of replicated state machines. In runs with no failures and no conflicts, Fast Paxos requires fewer communication steps for learners to learn of a request compared to Classic Paxos. However, there are realistic scenarios in which Classic Paxos has a significant probability of having a lower latency. This paper discusses one such scenario with an analytical comparison of the protocols and simulation results.

/pdf/classic-paxos-vs-fast-paxos-caveat-emptor-4e4lebu0mo.pdf

Classic Paxos vs. fast Paxos: caveat emptor

Smart Classroom is a Smart Space developed to enhance tele-education practice. This paper describes the considerations of bringing forward Smart Platform as the software infrastructure of Smart Classroom system, abandoning the former implementation based on OAA. As a multi-agent system for Smart Space, Smart Platform encompasses following features: spontaneous discovery of runtime environment, automatic management and resolving of agent dependencies, combination of delegated communication and peer-to-peer communication, etc. In addition, a surrogate agent on Smart Platform and Metaglue from MIT is now being developed to inter-connect Smart Classroom with MIT's Intelligent Room to extend their functionality.

Yanhua Mao

Papers

Mencius: building efficient replicated state machines for WANs

The smart classroom: merging technologies for seamless tele-education

Smart Platform - a software infrastructure for Smart Space (SISS)

Classic Paxos vs. fast Paxos: caveat emptor

Building the Software Infrastructure for Smart Classroom: From Open Agent Architecture (OAA) to Smart Platform