5,654 research outputs found
ACE: Abstract Consensus Encapsulation for Liveness Boosting of State Machine Replication
With the emergence of attack-prone cross-organization systems, providing asynchronous state machine replication (SMR) solutions is no longer a theoretical concern. This paper presents ACE, a framework for the design of such fault tolerant systems. Leveraging a known paradigm for randomized consensus solutions, ACE wraps existing practical solutions and real-life systems, boosting their liveness under adversarial conditions and, at the same time, promoting load balancing and fairness. Boosting is achieved without modifying the overall design or the engineering of these solutions.
ACE is aimed at boosting the prevailing approach for practical fault tolerance. This approach, often named partial synchrony, is based on a leader-based paradigm: a good leader makes progress and a bad leader does no harm. The partial synchrony approach focuses on safety and forgoes liveness under targeted and dynamic attacks. Specifically, an attacker might block specific leaders, e.g., through a denial of service, to prevent progress. ACE provides boosting by running waves of parallel leaders and selecting a winning leader only retroactively, achieving boosting at a linear communication cost increase.
ACE is agnostic to the fault model, inheriting it s failure model from the wrapped solution assumptions. As our evaluation shows, an asynchronous Byzantine fault tolerance (BFT) replication system built with ACE around an existing partially synchronous BFT protocol demonstrates reasonable slow-down compared with the base BFT protocol during faultless synchronous scenarios, yet exhibits significant speedup while the system is under attack
Millimeter Wave Ad Hoc Networks: Noise-limited or Interference-limited?
In millimeter wave (mmWave) communication systems, narrow beam operations
overcome severe channel attenuations, reduce multiuser interference, and thus
introduce the new concept of noise-limited mmWave wireless networks. The regime
of the network, whether noise-limited or interference-limited, heavily reflects
on the medium access control (MAC) layer throughput and on proper resource
allocation and interference management strategies. Yet, alternating presence of
these regimes and, more importantly, their dependence on the mmWave design
parameters are ignored in the current approaches to mmWave MAC layer design,
with the potential disastrous consequences on the throughput/delay performance.
In this paper, tractable closed-form expressions for collision probability and
MAC layer throughput of mmWave networks, operating under slotted ALOHA and
TDMA, are derived. The new analysis reveals that mmWave networks may exhibit a
non-negligible transitional behavior from a noise-limited regime to an
interference-limited regime, depending on the density of the transmitters,
density and size of obstacles, transmission probability, beamwidth, and
transmit power. It is concluded that a new framework of adaptive hybrid
resource allocation procedure, containing a proactive contention-based phase
followed by a reactive contention-free one with dynamic phase durations, is
necessary to cope with such transitional behavior.Comment: accepted in IEEE GLOBECOM'1
The Bedrock of Byzantine Fault Tolerance: A Unified Platform for BFT Protocol Design and Implementation
Byzantine Fault-Tolerant (BFT) protocols have recently been extensively used
by decentralized data management systems with non-trustworthy infrastructures,
e.g., permissioned blockchains. BFT protocols cover a broad spectrum of design
dimensions from infrastructure settings such as the communication topology, to
more technical features such as commitment strategy and even fundamental social
choice properties like order-fairness. The proliferation of different BFT
protocols has rendered it difficult to navigate the BFT landscape, let alone
determine the protocol that best meets application needs. This paper presents
Bedrock, a unified platform for BFT protocols design, analysis, implementation,
and experiments. Bedrock proposes a design space consisting of a set of design
choices capturing the trade-offs between different design space dimensions and
providing fundamentally new insights into the strengths and weaknesses of BFT
protocols. Bedrock enables users to analyze and experiment with BFT protocols
within the space of plausible choices, evolve current protocols to design new
ones, and even uncover previously unknown protocols. Our experimental results
demonstrate the capability of Bedrock to uniformly evaluate BFT protocols in
new ways that were not possible before due to the diverse assumptions made by
these protocols. The results validate Bedrock's ability to analyze and derive
BFT protocols
On-Line End-to-End Congestion Control
Congestion control in the current Internet is accomplished mainly by TCP/IP.
To understand the macroscopic network behavior that results from TCP/IP and
similar end-to-end protocols, one main analytic technique is to show that the
the protocol maximizes some global objective function of the network traffic.
Here we analyze a particular end-to-end, MIMD (multiplicative-increase,
multiplicative-decrease) protocol. We show that if all users of the network use
the protocol, and all connections last for at least logarithmically many
rounds, then the total weighted throughput (value of all packets received) is
near the maximum possible. Our analysis includes round-trip-times, and (in
contrast to most previous analyses) gives explicit convergence rates, allows
connections to start and stop, and allows capacities to change.Comment: Proceedings IEEE Symp. Foundations of Computer Science, 200
Parallel Deferred Update Replication
Deferred update replication (DUR) is an established approach to implementing
highly efficient and available storage. While the throughput of read-only
transactions scales linearly with the number of deployed replicas in DUR, the
throughput of update transactions experiences limited improvements as replicas
are added. This paper presents Parallel Deferred Update Replication (P-DUR), a
variation of classical DUR that scales both read-only and update transactions
with the number of cores available in a replica. In addition to introducing the
new approach, we describe its full implementation and compare its performance
to classical DUR and to Berkeley DB, a well-known standalone database
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