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

5G wireless networks are expected to support new applications demanding ultra high reliability and ultra low latency, such as self-driving cars, industrial control, and real-time gaming. Such services are known as ultra-reliable and low-latency communications (URLLC) targeting at 99.999% transmission correctness within 1 ms delay bound. Current Long Term Evolution (LTE) system is far from supporting such services, especially for uplink. Even with around 10 times shortened transmission interval, due to the waste of time in requesting and receiving the scheduling grant, only one shot uplink transmission can be supported within 1 ms, which is very hard to meet the reliability requirement. Grant-Free transmission is thus proposed to effectively save the time of requesting/waiting for grant and thus relax the transmission interval design in frame structure. This paper presents the design of grant-free transmission for URLLC services and also the evaluation results. We shall show that the saved time can be used for more Hybrid Automatic Repeat reQuest (HARQ) retransmissions and thus further enhance the reliability. Moreover, contention based grant-free transmission with proper HARQ design can well meet the reliability requirement. Finally, the performance can be further enhanced with non-orthogonal multiple access schemes such as Sparse Code Multiple Access (SCMA) and advanced receivers such as Message Passing Algorithm (MPA) or Expectation Propagation Algorithm (EPA) receiver.

Performance Evaluation of Grant-Free Transmission for Uplink URLLC Services

Overlay network distance monitoring and estimation system can benefit many new applications and services, such as peer-to-peer overlay routing and location. However, there is a lack of such scalable system with small overhead, good usability, and good distance estimation accuracy and stability. Thus we propose a scalable overlay distance monitoring system, Internet Iso-bar, which clusters hosts based on the similarity of their perceived network distance, with no assumption about the underlying network topology. The centers of each cluster are then chosen as monitors to represent their clusters for probing and distance estimation. We compare it with other network distance estimation systems, such as Global Network Positioning (GNP) [1]. Internet Iso-bar is easy to implement and use, and has good scalability and small communication and computation cost for online monitoring. Preliminary evaluation on real Internet measurement data also shows that Internet Iso-bar has high prediction accuracy and stability. Finally, by adjusting the number of clusters, we can smoothly trade off the measurement and management cost for better distance estimation accuracy and stability.

/pdf/on-the-stability-of-network-distance-estimation-a2picjbr97.pdf

On the stability of network distance estimation

https://hal-insu.archives-ouvertes.fr/insu-01406026/document

Tectonics and geodynamics of South China: An introductory note

Internet fault diagnosis is extremely important for end-users, overlay network service providers (like Akamai [), and even Internet service providers (ISPs). However, because link-level properties cannot be uniquely determined from end-to-end measurements, the accuracy of existing statistical diagnosis approaches is subject to uncertainty from statistical assumptions about the network. In this paper, we propose a novel least-biased end-to-end network diagnosis (in short, LEND) system for inferring link-level properties like loss rate. We define a minimal identifiable link sequence (MILS) as a link sequence of minimal length whose properties can be uniquely identified from end-to-end measurements. We also design efficient algorithms to find all the MILSs and infer their loss rates for diagnosis. Our LEND system works for any network topology and for both directed and undirected properties and incrementally adapts to network topology and property changes. It gives highly accurate estimates of the loss rates of MILSs, as indicated by both extensive simulations and Internet experiments. Furthermore, we demonstrate that such diagnosis can be achieved with fine granularity and in near real-time even for reasonably large overlay networks. Finally, LEND can supplement existing statistical inference approaches and provide smooth tradeoff between diagnosis accuracy and granularity.

/pdf/towards-unbiased-end-to-end-network-diagnosis-2rdoqlovov.pdf

Towards unbiased end-to-end network diagnosis

With the wide adoption, Linux-based IoT devices have emerged as one primary target of today's cyber attacks. Traditional malware-based attacks can quickly spread across these devices, but they are well-understood threats with effective defense techniques such as malware fingerprinting and community-based fingerprint sharing. Recently, fileless attacks---attacks that do not rely on malware files---have been increasing on Linux-based IoT devices, and posing significant threats to the security and privacy of IoT systems. Little has been known in terms of their characteristics and attack vectors, which hinders research and development efforts to defend against them. In this paper, we present our endeavor in understanding fileless attacks on Linux-based IoT devices in the wild. Over a span of twelve months, we deploy 4 hardware IoT honeypots and 108 specially designed software IoT honeypots, and successfully attract a wide variety of real-world IoT attacks. We present our measurement study on these attacks, with a focus on fileless attacks, including the prevalence, exploits, environments, and impacts. Our study further leads to multi-fold insights towards actionable defense strategies that can be adopted by IoT vendors and end users.

Yan Chen

Papers

Performance Evaluation of Grant-Free Transmission for Uplink URLLC Services

On the stability of network distance estimation

Tectonics and geodynamics of South China: An introductory note

Towards unbiased end-to-end network diagnosis

Understanding Fileless Attacks on Linux-based IoT Devices with HoneyCloud