A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node that stores a particular data item. This paper presents Chord, a distributed lookup protocol that addresses this problem. Chord provides support for just one operation: given a key, it maps the key onto a node. Data location can be easily implemented on top of Chord by associating a key with each data item, and storing the key/data item pair at the node to which the key maps. Chord adapts efficiently as nodes join and leave the system, and can answer queries even if the system is continuously changing. Results from theoretical analysis, simulations, and experiments show that Chord is scalable, with communication cost and the state maintained by each node scaling logarithmically with the number of Chord nodes.

Chord: A scalable peer-to-peer lookup service for internet applications

This paper presents the design and evaluation of Pastry, a scalable, distributed object location and routing substrate for wide-area peer-to-peer ap- plications. Pastry performs application-level routing and object location in a po- tentially very large overlay network of nodes connected via the Internet. It can be used to support a variety of peer-to-peer applications, including global data storage, data sharing, group communication and naming. Each node in the Pastry network has a unique identifier (nodeId). When presented with a message and a key, a Pastry node efficiently routes the message to the node with a nodeId that is numerically closest to the key, among all currently live Pastry nodes. Each Pastry node keeps track of its immediate neighbors in the nodeId space, and notifies applications of new node arrivals, node failures and recoveries. Pastry takes into account network locality; it seeks to minimize the distance messages travel, according to a to scalar proximity metric like the number of IP routing hops. Pastry is completely decentralized, scalable, and self-organizing; it automatically adapts to the arrival, departure and failure of nodes. Experimental results obtained with a prototype implementation on an emulated network of up to 100,000 nodes confirm Pastry's scalability and efficiency, its ability to self-organize and adapt to node failures, and its good network locality properties.

/pdf/pastry-scalable-decentralized-object-location-and-routing-1u2equbbbp.pdf

Pastry: Scalable, Decentralized Object Location, and Routing for Large-Scale Peer-to-Peer Systems

Hash tables - which map "keys" onto "values" - are an essential building block in modern software systems. We believe a similar functionality would be equally valuable to large distributed systems. In this paper, we introduce the concept of a Content-Addressable Network (CAN) as a distributed infrastructure that provides hash table-like functionality on Internet-like scales. The CAN is scalable, fault-tolerant and completely self-organizing, and we demonstrate its scalability, robustness and low-latency properties through simulation.

https://www.cs.sjtu.edu.cn/~gchen/course/acn/Reading/CAN.pdf

A scalable content-addressable network

A review of the geologic history of the Himalayan-Tibetan orogen suggests that at least 1400 km of north-south shortening has been absorbed by the orogen since the onset of the Indo-Asian collision at about 70 Ma. Significant crustal shortening, which leads to eventual construction of the Cenozoic Tibetan plateau, began more or less synchronously in the Eocene (50–40 Ma) in the Tethyan Himalaya in the south, and in the Kunlun Shan and the Qilian Shan some 1000–1400 km in the north. The Paleozoic and Mesozoic tectonic histories in the Himalayan-Tibetan orogen exerted a strong control over the Cenozoic strain history and strain distribution. The presence of widespread Triassic flysch complex in the Songpan-Ganzi-Hoh Xil and the Qiangtang terranes can be spatially correlated with Cenozoic volcanism and thrusting in central Tibet. The marked difference in seismic properties of the crust and the upper mantle between southern and central Tibet is a manifestation of both Mesozoic and Cenozoic tectonics. The form...

Geologic Evolution of the Himalayan-Tibetan Orogen

Reliability at massive scale is one of the biggest challenges we face at Amazon.com, one of the largest e-commerce operations in the world; even the slightest outage has significant financial consequences and impacts customer trust. The Amazon.com platform, which provides services for many web sites worldwide, is implemented on top of an infrastructure of tens of thousands of servers and network components located in many datacenters around the world. At this scale, small and large components fail continuously and the way persistent state is managed in the face of these failures drives the reliability and scalability of the software systems.This paper presents the design and implementation of Dynamo, a highly available key-value storage system that some of Amazon's core services use to provide an "always-on" experience. To achieve this level of availability, Dynamo sacrifices consistency under certain failure scenarios. It makes extensive use of object versioning and application-assisted conflict resolution in a manner that provides a novel interface for developers to use.

/pdf/dynamo-amazon-s-highly-available-key-value-store-2ozfk43ou4.pdf

Dynamo: amazon's highly available key-value store

In the Variscan French Massif Central, the Sillon Houiller Fault (SHF) is a major sub meridian discontinuity which kinematics, timing and evolution remain poorly understood. The spatial relationship of this accident with the surrounding granitic plutons suggests a genetic link between the SHF activity and pluton emplacement. The SHF is classically interpreted as a Late Carboniferous left-lateral wrench fault that might have accommodated a NW-SE and NE-SW extensional tectonics to theWest and East, respectively. However, this model disagrees with structural and geochronologic data that clearly show two successive and distinct extensional strain fields. Thus, in order to better understand the faulting process, the Montmarault granitic pluton, located along the western side of the Sillon Houiller fault, has been chosen as target for a multidisciplinary study. Monazite yields a chemical U-Th/Pb age of 321± 2Ma (i.e. Namurian) interpreted as the age of pluton emplacement. Thirty-seven sites of 214 drilling cores have been collected for the study of the Anisotropy of Magnetic Susceptibility (AMS). The biotite is identified as the main magnetic susceptibility carrier with an average of 150 μSI. However, few sites show very high magnetic susceptibility carried by magnetite which is suspected to be secondary mineral because these sites are located along on the contact with three Late Carboniferous coal basins. More than 39 % sites show well defined principal anisotropic axes. To constrain the structure of the granitic massif at depth, aeromagnetic and gravity data were interpreted. A complete Bouguer anomaly map of the Montmarault granite including existing data, supplemented by 525 new gravity stations, provides an average coverage of the area with about 1 station per km2. Based on rock density and magnetic susceptibility measurements, direct 2D joint gravity and magnetic modelling has been performed along several cross-sections. These studies allow us to draw the following conclusions. The Montmarault pluton exhibits a magnetic foliation dipping at high angle towards to the fault for those sites close to the fault and flat lying or gently dipping for other sites. The majority of sampled sites shows a consistently NW-SE trending magnetic lineation which is perpendicular to the Sillon Houiller fault. The important negative gravity anomaly along the fault and a weak anomaly to the west suggest that the Montmarault pluton is rooted along the SHF and spreads out northwestwards. Therefore, for the Namurian, the SHF cannot be considered as a transfer fault during but rather as a normal fault. These geometry and kinematics comply well with the overall late-orogenic regional extensional pattern at the scale of the whole Variscan French Massif Central. A preliminary 3D modelling of the pluton combining our new structural, AMS, gravity and aeromagnetic data, is also presented. Keywords: Granitic pluton, Anisotropy of Magnetic Susceptibility (AMS), European Variscan belt, Gravity and magnetic modelling, French Massif Central.

A multidisciplinary study on the Carboniferous (Namurian) Montmarault granitic pluton and its tectonic bearings on the activity of the Sillon Houiller Fault (Variscan Massif Central, France)

Despite the profound roles of surface deformation monitoring techniques in observing permafrost surface stability, predetermining the approximate location and time of possibly occurring severe permafrost degradation before applying these techniques is extremely necessary, but has received little attention. Taking the oil tank collapse accident in the Norilsk region as a case, we explored this concern by analyzing the permafrost deformation mechanisms and determining early surface deformation signals. Regarding this case, we firstly applied the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technique to obtain its permafrost surface deformation rate, then utilized a sine model to decompose its interannual deformation and seasonal deformation, and finally compared the relationship between the topographic slope and deformation rate. Based on experimental results, we reveal that when the annual average temperature continuously increases at a rate of 2 °C/year for 2∼3 consecutive years, permafrost areas with relatively large topographic slopes (>15°) are more prone to severe surface deformation during the summer thaw period. Therefore, this paper suggests that permafrost areas with large topographic slopes (>15°) should be taken as the key surveillance areas, and that the appropriate monitoring time for employing surface deformation monitoring techniques should be the summer thawing period after a continuous increase in annual average temperature at a rate of 2 °C/year for 2∼3 years.

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Permafrost Early Deformation Signals before the Norilsk Oil Tank Collapse in Russia

A late jurassic paleomagnetic study in southwestern border of Tarim Basin.

Emplacement mechanism of the Middle-Late Jurassic Qitianling pluton and its implications on the Mesozoic tectonics of South China Block

Denial of Service (DoS) attacks are increasing in frequency, severity and sophistication. Most previous work has focused on DoS attacks which take advantage of a protocol to launch the attack. We take the view that DoS attack is any malicious action which reduces the availability of some resource to some users. We set as a goal a general methodology for measuring the resilience of a system to broad classes of attacks. As a first step toward this ambitious goal, we have studied the effect of a variety of attacks on directory services in a network setting.

Yan Chen

Papers

A multidisciplinary study on the Carboniferous (Namurian) Montmarault granitic pluton and its tectonic bearings on the activity of the Sillon Houiller Fault (Variscan Massif Central, France)

Permafrost Early Deformation Signals before the Norilsk Oil Tank Collapse in Russia

A late jurassic paleomagnetic study in southwestern border of Tarim Basin.

Emplacement mechanism of the Middle-Late Jurassic Qitianling pluton and its implications on the Mesozoic tectonics of South China Block

Quantitative Characterization of Denial of Service: A Location Service Case Study