Loo, Boon Thau
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Publication MOSAIC: Multiple Overlay Selection and Intelligent Composition(2007-10-24) Loo, Boon Thau; Ives, Zachary G; Mao, Yun; Smith, Jonathan MToday, the most effective mechanism for remedying shortcomings of the Internet, or augmenting it with new networking capabilities, is to develop and deploy a new overlay network. This leads to the problem of multiple networking infrastructures, each with independent advantages, and each developed in isolation. A greatly preferable solution is to have a single infrastructure under which new overlays can be developed, deployed, selected, and combined according to application and administrator needs. MOSAIC is an extensible infrastructure that enables not only the specification of new overlay networks, but also dynamic selection and composition of such overlays. MOSAIC provides declarative networking: it uses a unified declarative language (Mozlog) and runtime system to enable specification of new overlay networks, as well as their composition in both the control and data planes. Importantly, it permits dynamic compositions with both existing overlay networks and legacy applications. This paper demonstrates the dynamic selection and composition capabilities of MOSAIC with a variety of declarative overlays: an indirection overlay that supports mobility (i3), a resilient overlay (RON), and a transport-layer proxy. Using a remarkably concise specification, MOSAIC provides the benefits of runtime composition to simultaneously deliver application-aware mobility, NAT traversal and reliability with low performance overhead, demonstrated with deployment and measurement on both a local cluster and the PlanetLab testbed.Publication Analyzing P2P Overlays with Recursive Queries(2003-11-01) Loo, Boon Thau; Huebsch, Ryan; Hellerstein, Joseph M; Roscoe, Timothy; Stoica, IonWe explore the utility and execution of recursive queries as an interface for querying distributed network graph structures. To illustrate the power of recursive queries, we give several examples of computing structural properties of a P2P network such as reachability and resilience. To demonstrate the feasibility of our proposal, we sketch execution strategies for these queries using PIER, a P2P relational query processor over Distributed Hash Tables (DHTs). Finally, we discuss the relationship between in-network query processing and distance-vector like routing protocols.Publication Provenance-Aware Declarative Secure Networks(2007-12-05) Zhou, Wenchao; Cronin, Eric; Loo, Boon ThauIn recent years, network accountability and forensic analysis have become increasingly important, as a means of performing network diagnostics, identifying malicious nodes, enforcing trust management policies, and imposing diverse billing over the Internet. This has lead to a series of work to provide better network support for accountability, and efficient mechanisms to trace packets and information flows through the Internet. In this paper, we make the following contributions. First, we show that network accountability and forensic analysis can be posed generally as data provenance computations and queries over distributed streams. In particular, one can utilize provenance-aware declarative networks with appropriate security extensions to provide a flexible declarative framework for specifying, analyzing and auditing networks. Second, we propose a taxonomy of data provenance along multiple axes, and show that they map naturally to different use cases in networks. Third, we suggest techniques to efficiently compute and store network provenance, and provide an initial performance evaluation on the P2 declarative networking system with modifications to support provenance and authenticated communication.Publication Declarative Automated Cloud Resource Orchestration(2011-10-01) Liu, CHangbin; Loo, Boon Thau; Mao, YunAs cloud computing becomes widely deployed, one of the challenges faced involves the ability to orchestrate a highly complex set of subsystems (compute, storage, network resources) that span large geographic areas serving diverse clients. To ease this process, we present COPE (Cloud Orchestration Policy Engine), a distributed platform that allows cloud providers to perform declarative automated cloud resource orchestration. In COPE, cloud providers specify system-wide constraints and goals using COPElog, a declarative policy language geared towards specifying distributed constraint optimizations. COPE takes policy specifications and cloud system states as input and then optimizes compute, storage and network resource allocations within the cloud such that provider operational objectives and customer SLAs can be better met. We describe our proposed integration with a cloud orchestration platform, and present initial evaluation results that demonstrate the viability of COPE using production traces from a large hosting company in the US. We further discuss an orchestration scenario that involves geographically distributed data centers, and conclude with an ongoing status of our work.Publication DMaC: Distributed Monitoring and Checking(2009-06-01) Zhou, Wenchao; Sokolsky, Oleg; Loo, Boon Thau; Lee, InsupWe consider monitoring and checking formally specified properties in a network. We are addressing the problem of deploying the checkers on different network nodes that provide correct and efficient checking. We present the DMaC system that builds upon two bodies of work: the Monitoring and Checking (MaC) framework, which provides means to monitor and check running systems against formally specified requirements, and declarative networking, a declarative domain-specific approach for specifying and implementing distributed network protocols. DMaC uses a declarative networking system for both specifying network protocols and performing checker execution. High-level properties are automatically translated from safety property specifications in the MaC framework into declarative networking queries and integrated into the rest of the network for monitoring the safety properties. We evaluate the flexibility and efficiency of DMaC using simple but realistic network protocols and their propertiesPublication Experiences in Teaching an Educational User-Level Operating Systems Implementation Project(2012-01-01) Aviv, Adam J; Mannino, Vin; Owlarn, Thanat; Shannin, Seth; Xu, Kevin; Loo, Boon ThauThe importance of a comprehensive implementation component for undergraduate Operating Systems (OS) courses cannot be understated. Students not only develop deep insight and understanding of OS fundamentals, but they also learn key software engineering skills that only a large development project, such as implementing an OS, can teach. There are clear benefits to traditional OS projects where students program or alter real (Linux) kernel source or extend educational OS implementations; however, in our experience, bootstrapping such a project is a huge undertaking that may not be accessible in many classrooms. In this paper, we describe a different approach to the OS implementation assignment: A user-level Operating System simulation based on UNIX preemptive signaling and threading constructs called ucontext. We believe that this variation of the implementation assignment provides many of the same educational benefits as traditional low-level projects without many of the expensive start-up costs. This project has been taught for a number of years at the University of Pennsylvania and was recently overhauled for the Fall 2011 semester. This paper describes the current version of the project and our experiences teaching it to a class of 54 students.Publication Recent Advances in Declarative Networking(2012-01-01) Loo, Boon Thau; Gill, Harjot; Liu, Changbin; Mao, Yun; Marczak, William R.; Sherr, Micah; Wang, Anduo; Zhuo, WenchaoDeclarative networking is a programming methodology that enables developers to concisely specify network protocols and services, and directly compile these specifications into a dataflow framework for execution. This paper describes recent advances in declarative networking, tracing its evolution from a rapid prototyping framework towards a platform that serves as an important bridge connecting formal theories for reasoning about protocol correctness and actual implementations. In particular, the paper focuses on the use of declarative networking for addressing four main challenges in the distributed systems development cycle: the generation of safe routing implementations, debugging, security and privacy, and optimizing distributed systems.Publication Querying and Routing in Next-Generation Networks(2004-08-01) Loo, Boon ThauI propose the use of recursive queries [24] as an interface for querying distributed network graph structures. Recursive queries allow a query result to be defined in terms of itself. This is particularly useful for querying network graphs that exhibit recursive structures. To query these distributed graphs over the Internet, I propose using distributed query processing techniques to process recursive queries. I further demonstrate the relationship between in-network execution of recursive queries and traditional routing protocols. Based on this relationship, I propose investigating the use of recursive queries for end-hosts to customize routing protocols. I plan to implement my proposals in the context of the PIER [9] system, and study different techniques to achieve good performance in the system.Publication Towards Self-Explaining Networks(2011-06-01) Zhou, Wenchao; Haeberlen, Andreas; Fei, Qiong; Loo, Boon Thau; Sherr, MicahIn this paper, we argue that networks should be able to explain to their operators why they are in a certain state, even if – and particularly if – they have been compromised by an attacker. Such a capability would be useful in forensic investigations, where an operator observes an unexpected state and must decide whether it is benign or an indication that the system has been compromised. Using a very pessimistic threat model in which a malicious adversary can completely compromise an arbitrary subset of the nodes in the network, we argue that we cannot expect to get a complete and correct explanation in all possible cases. However, we also show that, based on recent advances in the systems and the database communities, it seems possible to get a slightly weaker guarantee: for any state change that directly or indirectly affects a correct node, we can either obtain a correct explanation or eventually identify at least one compromised node. We discuss the challenges involved in building systems that provide this property, and we report initial results from an early prototype.Publication A Reduction-Based Approach Towards Scaling Up Formal Analysis of Internet Configurations(2013-01-01) Wang, Anduo; Gurney, Alexander JT; Han, Xianglong; Cao, Jinyan; Loo, Boon T; Talcott, Carolyn; Scedrov, AndreThe Border Gateway Protocol (BGP) is the single inter-domain routing protocol that enables network operators within each autonomous system (AS) to influence routing decisions by independently setting local policies on route filtering and selection. This independence leads to fragile networking and makes analysis of policy configurations very complex. To aid the systematic and efficient study of the policy configuration space, this paper presents network reduction, a scalability technique for policy-based routing systems. In network reduction, we provide two types of reduction rules that transform policy configurations by merging duplicate and complementary router configurations to simplify analysis. We show that the reductions are sound, dual of each other and are locally complete. The reductions are also computationally attractive, requiring only local configuration information and modification. We have developed a prototype of network reduction and demonstrated that it is applicable on various BGP systems and enables significant savings in analysis time. In addition to making possible safety analysis on large networks that would otherwise not complete within reasonable time, network reduction is also a useful tool for discovering possible redundancies in BGP systems.