19,716 research outputs found
Replication Control in Distributed File Systems
We present a replication control protocol for distributed file systems that can guarantee strict consistency or sequential consistency while imposing no performance overhead for normal reads. The protocol uses a primary-copy scheme with server redirection when concurrent writes occur. It tolerates any number of component omission and performance failures, even when these lead to network partition. Failure detection and recovery are driven by client accesses. No heartbeat messages or expensive group communication services are required. We have implemented the protocol in NFSv4, the emerging Internet standard for distributed filing.http://deepblue.lib.umich.edu/bitstream/2027.42/107880/1/citi-tr-04-1.pd
State of The Art and Hot Aspects in Cloud Data Storage Security
Along with the evolution of cloud computing and cloud storage towards matu-
rity, researchers have analyzed an increasing range of cloud computing security
aspects, data security being an important topic in this area. In this paper, we
examine the state of the art in cloud storage security through an overview of
selected peer reviewed publications. We address the question of defining cloud
storage security and its different aspects, as well as enumerate the main vec-
tors of attack on cloud storage. The reviewed papers present techniques for key
management and controlled disclosure of encrypted data in cloud storage, while
novel ideas regarding secure operations on encrypted data and methods for pro-
tection of data in fully virtualized environments provide a glimpse of the toolbox
available for securing cloud storage. Finally, new challenges such as emergent
government regulation call for solutions to problems that did not receive enough
attention in earlier stages of cloud computing, such as for example geographical
location of data. The methods presented in the papers selected for this review
represent only a small fraction of the wide research effort within cloud storage
security. Nevertheless, they serve as an indication of the diversity of problems
that are being addressed
Naming, Migration, and Replication for NFSv4
In this paper, we discuss a global name space for NFSv4 and mechanisms for transparent migration and replication. By convention, any file or directory name beginning with /nfs on an NFS client is part of this shared global name space. Our system supports file system migration and replication through DNS resolution, provides directory migration and replication using built-in NFSv4 mechanisms, and supports read/write replication with precise consistency guarantees, small performance penalty, and good scaling. We implement these features with small extensions to the published NFSv4 protocol, and demonstrate a practical way to enhance network transparency and administerability of NFSv4 in wide area networks.http://deepblue.lib.umich.edu/bitstream/2027.42/107939/1/citi-tr-06-1.pd
Resilient networking in wireless sensor networks
This report deals with security in wireless sensor networks (WSNs),
especially in network layer. Multiple secure routing protocols have been
proposed in the literature. However, they often use the cryptography to secure
routing functionalities. The cryptography alone is not enough to defend against
multiple attacks due to the node compromise. Therefore, we need more
algorithmic solutions. In this report, we focus on the behavior of routing
protocols to determine which properties make them more resilient to attacks.
Our aim is to find some answers to the following questions. Are there any
existing protocols, not designed initially for security, but which already
contain some inherently resilient properties against attacks under which some
portion of the network nodes is compromised? If yes, which specific behaviors
are making these protocols more resilient? We propose in this report an
overview of security strategies for WSNs in general, including existing attacks
and defensive measures. In this report we focus at the network layer in
particular, and an analysis of the behavior of four particular routing
protocols is provided to determine their inherent resiliency to insider
attacks. The protocols considered are: Dynamic Source Routing (DSR),
Gradient-Based Routing (GBR), Greedy Forwarding (GF) and Random Walk Routing
(RWR)
Resilient Cloud-based Replication with Low Latency
Existing approaches to tolerate Byzantine faults in geo-replicated
environments require systems to execute complex agreement protocols over
wide-area links and consequently are often associated with high response times.
In this paper we address this problem with Spider, a resilient replication
architecture for geo-distributed systems that leverages the availability
characteristics of today's public-cloud infrastructures to minimize complexity
and reduce latency. Spider models a system as a collection of loosely coupled
replica groups whose members are hosted in different cloud-provided fault
domains (i.e., availability zones) of the same geographic region. This
structural organization makes it possible to achieve low response times by
placing replica groups in close proximity to clients while still enabling the
replicas of a group to interact over short-distance links. To handle the
inter-group communication necessary for strong consistency Spider uses a
reliable group-to-group message channel with first-in-first-out semantics and
built-in flow control that significantly simplifies system design.Comment: 25 pages, extended version of Middleware 2020 pape
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