Ashvin Goel

Haggle: seamless networking for mobile applications

This paper presents Haggle, an architecture for mobile devices that enables seamless network connectivity and application functionality in dynamic mobile environments. Current applications must contain significant network binding and protocol logic, which makes them inflexible to the dynamic networking environments facing mobile devices. Haggle allows separating application logic from transport bindings so that applications can be communication agnostic. Internally, the Haggle framework provides a mechanism for late-binding interfaces, names, protocols, and resources for network communication. This separation allows applications to easily utilize multiple communication modes and methods across infrastructure and infrastructure-less environments. We provide a prototype implementation of the Haggle framework and evaluate it by demonstrating support for two existing legacy applications, email and web browsing. Haggle makes it possible for these applications to seamlessly utilize mobile networking opportunities both with and without infrastructure.

User mobility for opportunistic ad-hoc networking

As mobile devices become increasingly pervasive and commonly equipped with short-range radio capabilities, we observe that it might be possible to build a network based only on pair-wise contact of users. By using user mobility as a network transport mechanism, devices can intelligently route latency-insensitive packets using power-efficient short-range radio. Such a network could provide communication capability where no network infrastructure exists, or extend the reach of established infrastructure. To collect user mobility data, we ran two user studies by giving instrumented PDA devices to groups of students to carry for several weeks. We evaluate our work by providing empirical data that suggests that it is possible to make intelligent routing decisions based on only pair-wise contact, without previous knowledge of the mobility model or location information.

The taser intrusion recovery system

Recovery from intrusions is typically a very time-consuming operation in current systems. At a time when the cost of human resources dominates the cost of computing resources, we argue that next generation systems should be built with automated intrusion recovery as a primary goal. In this paper, we describe the design of Taser, a system that helps in selectively recovering legitimate file-system data after an attack or local damage occurs. Taser reverts tainted, i.e. attack-dependent, file-system operations but preserves legitimate operations. This process is difficult for two reasons. First, the set of tainted operations is not known precisely. Second, the recovery process can cause conflicts when legitimate operations depend on tainted operations. Taser provides several analysis policies that aid in determining the set of tainted operations. To handle conflicts, Taser uses automated resolution policies that isolate the tainted operations. Our evaluation shows that Taser is effective in recovering from a wide range of intrusions as well as damage caused by system management errors.

A preliminary investigation of worm infections in a bluetooth environment

Over the past year, there have been several reports of malicious code exploiting vulnerabilities in the Bluetooth protocol. While the research community has started to investigate a diverse set of Bluetooth security issues, little is known about the feasibility and the propagation dynamics of a worm in a Bluetooth environment. This paper is an initial attempt to remedy this situation.We start by showing that the Bluetooth protocol design and implementation is large and complex. We gather traces and we use controlled experiments to investigate whether a large-scale Bluetooth worm outbreak is viable today. Our data shows that starting a Bluetooth worm infection is easy, once a vulnerability is discovered. Finally, we use trace-drive simulations to examine the propagation dynamics of Bluetooth worms. We find that Bluetooth worms can infect a large population of vulnerable devices relatively quickly, in just a few days.

Reconstructing system state for intrusion analysis

The analysis of a compromised system is a time-consuming and error-prone task today because commodity operating systems provide limited auditing facilities. We have been developing an operating-system level auditing system called Forensix that captures a high-resolution image of all system activities so that detailed analysis can be performed after an attack is detected. The challenge with this approach is that the large amount of audit data generated can overwhelm analysis tools. In this paper, we describe a technique that helps generate a time-line of the state of the system. This technique, based on preprocessing the audit log, simplifies the implementation of the analysis queries and enables running the analysis tools interactively on large data sets.

Specialization tools and techniques for systematic optimization of system software

Specialization has been recognized as a powerful technique for optimizing operating systems. However, specialization has not been broadly applied beyond the research community because current techniques based on manual specialization, are time-consuming and error-prone. The goal of the work described in this paper is to help operating system tuners perform specialization more easily. We have built a specialization toolkit that assists the major tasks of specializing operating systems. We demonstrate the effectiveness of the toolkit by applying it to three diverse operating system components. We show that using tools to assist specialization enables significant performance optimizations without error-prone manual modifications. Our experience with the toolkit suggests new ways of designing systems that combine high performance and clean structure.

A measurement-based analysis of the real-time performance of linux

This paper presents an experimental study of the latency behavior of the Linux OS. We identify major sources of latency in the kernel with the goal of providing real-time performance in a widely used general-purpose operating system. We quantify, each source of latency with a series of micro-benchmarks and also evaluate the effects of latency on a time-sensitive application. Our analysis shows that there are two main causes of latency in the OS: tinier resolution and non-preemptable sections. Our experiments show that in the standard Linux kernel the tinier resolution latency is predominant, and generally hides the non-preemptable section latency We use accurate timers to reduce timer resolution latency and then analyze the non-preemptable section latency for several variants of Linux.

Fast, optimized Sun RPC using automatic program specialization

Fast remote procedure call (RPC) is a major concern for distributed systems. Many studies aimed at efficient RPC consist of either new implementations of the RPC paradigm or manual optimization of critical sections of the code. This paper presents an experiment that achieves automatic optimization of an existing, commercial RPC implementation, namely the Sun RPC. The optimized Sun RPC is obtained by using an automatic program specializer. It runs up to 1.5 times faster than the original Sun RPC. Close examination of the specialized code does not reveal further optimization opportunities which would lead to significant improvements without major manual restructuring. The contributions of this work are: the optimized code is safely produced by an automatic tool and thus does not entail any additional maintenance; to the best of our knowledge this is the first successful specialization of mature, commercial, representative system code; and the optimized Sun RPC runs significantly faster than the original code.

Timbremap: enabling the visually-impaired to use maps on touch-enabled devices

Mapping applications on mobile devices have gained widespread popularity as a means for enhancing user mobility and ability to explore new locations and venues. Visually impaired users currently rely on computer text-to-speech or human-spoken descriptions of maps and indoor spaces. Unfortunately, speech-based descriptions are limited in their ability to succinctly convey complex layouts or spacial positioning. This paper presents Timbremap, a sonification interface enabling visually impaired users to explore complex indoor layouts using off-the-shelf touch-screen mobile devices. This is achieved using audio feedback to guide the users finger on the devices touch interface to convey geometry. Our user-study evaluation shows Timbremap is effective in conveying non-trivial geometry and enabling visually impaired users to explore indoor layouts.

Supporting low latency TCP-based media streams

The dominance of the TCP protocol on the Internet and its success in maintaining Internet stability has led to several TCP-based stored media-streaming approaches. The success of these approaches raises the question whether TCP can be used for low-latency streaming. Low latency streaming allows responsive control operations for media streaming and can make interactive applications feasible. We examined adapting the TCP send buffer size based on TCPs congestion window to reduce application perceived network latency. Our results show that this simple idea significantly improves the number of packets that can be delivered within 200 ms and 500 ms thresholds.