Ben Y. Zhao

OceanStore: an architecture for global-scale persistent storage

OceanStore is a utility infrastructure designed to span the globe and provide continuous access to persistent information. Since this infrastructure is comprised of untrusted servers, data is protected through redundancy and cryptographic techniques. To improve performance, data is allowed to be cached anywhere, anytime. Additionally, monitoring of usage patterns allows adaptation to regional outages and denial of service attacks; monitoring also enhances performance through pro-active movement of data. A prototype implementation is currently under development.

Tapestry: a resilient global-scale overlay for service deployment

We present Tapestry, a peer-to-peer overlay routing infrastructure offering efficient, scalable, location-independent routing of messages directly to nearby copies of an object or service using only localized resources. Tapestry supports a generic decentralized object location and routing applications programming interface using a self-repairing, soft-state-based routing layer. The paper presents the Tapestry architecture, algorithms, and implementation. It explores the behavior of a Tapestry deployment on PlanetLab, a global testbed of approximately 100 machines. Experimental results show that Tapestry exhibits stable behavior and performance as an overlay, despite the instability of the underlying network layers. Several widely distributed applications have been implemented on Tapestry, illustrating its utility as a deployment infrastructure.

Bayeux: an architecture for scalable and fault-tolerant wide-area data dissemination

The demand for streaming multimedia applications is growing at an incr edible rate. In this paper, we propose Bayeux, an efficient application-level multicast system that scales to arbitrarily large receiver groups while tolerating failures in routers and network links. Bayeux also includes specific mechanisms for load-balancing across replicate root nodes and more efficient bandwidth consumption. Our simulation results indicate that Bayeux maintains these properties while keeping transmission overhead low. To achieve these properties, Bayeux leverages the architecture of Tapestry, a fault-tolerant, wide-area overlay routing and location network.

An architecture for a secure service discovery service

The widespread deployment of inexpensive communications technology, computational resources in the networking infrastructure, and network-enabled end devices poses an interesting problem for end users: how to locate a particular network service or device out of hundreds of thousands of accessible services and devices. This paper presents the architecture and implementation of a secure Service Discovery Service (SDS). Service providers use the SDS to advertise complex descriptions of available or already running services, while clients use the SDS to compose complex queries for locating these services. Service descriptions and queries use the eXtensible Markup Language (XML) to encode such factors as cost, performance, location, and deviceor service-specific capabilities. The SDS provides a highlyavailable, fault-tolerant, incrementally scalable service for locating services in the wide-area. Security is a core component of the SDS and, where necessary, communications are both encrypted and authenticated. Furthermore, the SDS uses an hybrid access control list and capability system to control access to service information.

Utilization and fairness in spectrum assignment for opportunistic spectrum access

The Open Spectrum approach to spectrum access can achieve near-optimal utilization by allowing devices to sense and utilize available spectrum opportunistically. However, a naive distributed spectrum assignment can lead to significant interference between devices. In this paper, we define a general framework that defines the spectrum access problem for several definitions of overall system utility. By reducing the allocation problem to a variant of the graph coloring problem, we show that the global optimization problem is NP-hard, and provide a general approximation methodology through vertex labeling. We examine both a centralized strategy, where a central server calculates an allocation assignment based on global knowledge, and a distributed approach, where devices collaborate to negotiate local channel assignments towards global optimization. Our experimental results show that our allocation algorithms can dramatically reduce interference and improve throughput (as much as 12-fold). Further simulations show that our distributed algorithms generate allocation assignments similar in quality to our centralized algorithms using global knowledge, while incurring substantially less computational complexity in the process.

Detecting and characterizing social spam campaigns

Online social networks (OSNs) are exceptionally useful collaboration and communication tools for millions of users and their friends. Unfortunately, in the wrong hands, they are also extremely effective tools for executing spam campaigns and spreading malware. In this poster, we present an initial study to detect and quantitatively analyze the coordinated spam campaigns on online social networks in the wild. Our system detected about 200K malicious wall posts with embedded URLs, traced back to roughly 57K accounts. We find that more than 70% of all malicious wall posts are advertising phishing sites

Maintenance-free global data storage

Explores mechanisms for storage-level management in OceanStore, a global-scale distributed storage utility infrastructure, designed to scale to billions of users and exabytes of data. OceanStore automatically recovers from server and network failures, incorporates new resources and adjusts to usage patterns. It provides its storage platform through adaptation, fault tolerance and repair. The only role of human administrators in the system is to physically attach or remove server hardware. Of course, an open question is how to scale a research prototype in such a way to demonstrate the basic thesis of this article - that OceanStore is self-maintaining. The allure of connecting millions or billions of components together is the hope that aggregate systems can provide scalability and predictable behavior under a wide variety of failures. The OceanStore architecture is a step towards this goal.

Brocade: Landmark Routing on Overlay Networks

Recent work such as Tapestry, Pastry, Chord and CAN provide efficient location utilities in the form of overlay infrastructures. These systems treat nodes as if they possessed uniform resources, such as network bandwidth and connectivity. In this paper, we propose a systemic design for a secondaryoverlay of super-nodes which can be used to deliver messages directly to the destinations local network, thus improving route efficiency. We demonstrate the potential performance benefits by proposing a name mapping scheme for a Tapestry-Tapestry secondary overlay, and show preliminary simulation results demonstrating significant routing performance improvement.

The Ninja architecture for robust Internet-scale systems and services373423

Abstract The Ninja project seeks to enable the broad innovation of robust, scalable, distributed Internet services, and to permit the emerging class of extremely heterogeneous devices to seamlessly access these services. Our architecture consists of four basic elements: bases, which are powerful workstation cluster environments with a software platform that simplifies scalable service construction; units, which are the devices by which users access the services; active proxies, which are transformational elements that are used for unit- or service-specific adaptation; and paths, which are an abstraction through which units, services, and active proxies are composed.

Parallelizing skyline queries for scalable distribution

Skyline queries help users make intelligent decisions over complex data, where different and often conflicting criteria are considered. Current skyline computation methods are restricted to centralized query processors, limiting scalability and imposing a single point of failure. In this paper, we address the problem of parallelizing skyline query execution over a large number of machines by leveraging content-based data partitioning. We present a novel distributed skyline query processing algorithm (DSL) that discovers skyline points progressively. We propose two mechanisms, recursive region partitioning and dynamic region encoding, to enforce a partial order on query propagation in order to pipeline query execution. Our analysis shows that DSL is optimal in terms of the total number of local query invocations across all machines. In addition, simulations and measurements of a deployed system show that our system load balances communication and processing costs across cluster machines, providing incremental scalability and significant performance improvement over alternative distribution mechanisms.