Richard Mortier

ThinkAir: Dynamic resource allocation and parallel execution in the cloud for mobile code offloading

Smartphones have exploded in popularity in recent years, becoming ever more sophisticated and capable. As a result, developers worldwide are building increasingly complex applications that require ever increasing amounts of computational power and energy. In this paper we propose ThinkAir, a framework that makes it simple for developers to migrate their smartphone applications to the cloud. ThinkAir exploits the concept of smartphone virtualization in the cloud and provides method-level computation offloading. Advancing on previous work, it focuses on the elasticity and scalability of the cloud and enhances the power of mobile cloud computing by parallelizing method execution using multiple virtual machine (VM) images. We implement ThinkAir and evaluate it with a range of benchmarks starting from simple micro-benchmarks to more complex applications. First, we show that the execution time and energy consumption decrease two orders of magnitude for a N-queens puzzle application and one order of magnitude for a face detection and a virus scan application. We then show that a parallelizable application can invoke multiple VMs to execute in the cloud in a seamless and on-demand manner such as to achieve greater reduction on execution time and energy consumption. We finally use a memory-hungry image combiner tool to demonstrate that applications can dynamically request VMs with more computational power in order to meet their computational requirements.

Unikernels: library operating systems for the cloud

We present unikernels, a new approach to deploying cloud services via applications written in high-level source code. Unikernels are single-purpose appliances that are compile-time specialised into standalone kernels, and sealed against modification when deployed to a cloud platform. In return they offer significant reduction in image sizes, improved efficiency and security, and should reduce operational costs. Our Mirage prototype compiles OCaml code into unikernels that run on commodity clouds and offer an order of magnitude reduction in code size without significant performance penalty. The architecture combines static type-safety with a single address-space layout that can be made immutable via a hypervisor extension. Mirage contributes a suite of type-safe protocol libraries, and our results demonstrate that the hypervisor is a platform that overcomes the hardware compatibility issues that have made past library operating systems impractical to deploy in the real-world.

Plutarch: an argument for network pluralism

It is widely accepted that the current Internet architecture is insufficient for the future: problems such as address space scarcity, mobility and non-universal connectivity are already with us, and stand to be exacerbated by the explosion of wireless, ad-hoc and sensor networks. Furthermore, it is far from clear that the ubiquitous use of standard transport and name resolution protocols will remain practicable or even desirable.In this paper we propose Plutarch, a new inter-networking architecture. It subsumes existing architectures such as that determined by the Internet Protocol suite, but makes explicit the heterogeneity that contemporary inter-networking schemes attempt to mask. To handle this heterogeneity, we introduce the notions of context and interstitial function, and describe a supporting architecture. We discuss the benefits, present some potential scenarios, and consider the research challenges posed.

Network topologies: inference, modeling, and generation

Accurate measurement, inference and modeling techniques are fundamental to Internet topology research. Spatial analysis of the Internet is needed to develop network planning, optimal routing algorithms, and failure detection measures. A first step toward achieving such goals is the availability of network topologies at different levels of granularity, facilitating realistic simulations of new Internet systems. The main objective of this survey is to familiarize the reader with research on network topology over the past decade. We study techniques for inference, modeling, and generation of the Internet topology at both the router and administrative levels. We also compare the mathematical models assigned to various topologies and the generation tools based on them. We conclude with a look at emerging areas of research and potential future research directions.

Detection and analysis of routing loops in packet traces

Routing loops are caused by inconsistencies in routing state among a set of routers. They occur in perfectly engineered networks, and have a detrimental effect on performance. They impact end-to-end performance through increased packet loss and delay for packets caught in the loop, and through increased link utilization and corresponding delay and jitter for packets that traverse the link but are not caught in the loop.Using packet traces from a tier-1 ISP backbone, we first explain how routing loops manifest in packet traces. We characterize routing loops in terms of the packet types caught in the loop, the loop sizes, and the loop durations. Finally, we analyze the impact of routing loops on network performance in terms of loss and delay.

Implicit admission control

Internet protocols currently use packet-level mechanisms to detect and react to congestion. Although these controls are essential to ensure fair sharing of the available resource between multiple flows, in some cases they are insufficient to ensure overall network stability. We believe that it is also necessary to take account of higher level concepts, such as connections, flows, and sessions when controlling network congestion. This becomes of increasing importance as more real-time traffic is carried on the Internet, since this traffic is less elastic in nature than traditional Web traffic. We argue that, in order to achieve better utility of the network as a whole, higher level congestion controls are required. By way of example, we present a simple connection admission control (CAC) scheme which can significantly improve the overall performance. This paper discusses our motivation for the use of admission control in the Internet, focusing specifically on control for TCP flows. The technique is not TCP specific, and can be applied to any type of flow in a modern IP infrastructure. Simulation results are used to show that it can drastically improve the performance of TCP over bottleneck links. We go on to describe an implementation of our algorithm for a router running the Linux 2.2.9 operating system. We show that by giving routers at bottlenecks the ability to intelligently deny admission to TCP connections, the goodput of existing connections can be significantly increased. Furthermore, the fairness of the resource allocation achieved by TCP is improved.

Weighted spectral distribution for internet topology analysis: theory and applications

Comparing graphs to determine the level of underlying structural similarity between them is a widely encountered problem in computer science. It is particularly relevant to the study of Internet topologies, such as the generation of synthetic topologies to represent the Internets AS topology. We derive a new metric that enables exactly such a structural comparison: the weighted spectral distribution. We then apply this metric to three aspects of the study of the Internets AS topology. i) We use it to quantify the effect of changing the mixing properties of a simple synthetic network generator. ii) We use this quantitative understanding to examine the evolution of the Internets AS topology over approximately seven years, finding that the distinction between the Internet core and periphery has blurred over time. iii) We use the metric to derive optimal parameterizations of several widely used AS topology generators with respect to a large-scale measurement of the real AS topology.

QoS's downfall: at the bottom, or not at all!

Quality of Service (QoS) has been touted as a technological requirement for many different networks at many different times. However, very few (if any) schemes for providing it have ever been successful, despite a huge amount of research in the area of QoS provision. In this position paper we analyze some of the reasons why so many QoS mechanisms have failed to be widely deployed. We suggest two factors in this failure: the timeliness of QoS mechanisms (they rarely arrive when they are needed), and the inherent contradiction of layering QoS mechanisms over a best-effort network. We also give some thoughts on how future QoS research might increase its chances of successful deployment by better positioning itself relative to other developments in networking.

Autonomic network management: some pragmatic considerations

Autonomic Network Management (ANM) has the goal of increasing reliability and performance while reducing management cost using various automated techniques. These range from agent-based approaches relying on explicit models and ontologies to emergent techniques relying on gossip protocols, swarming algorithms or other biologically inspired work. In this paper, we review the failures, growing pains and successes of earlier techniques for automated and adaptive network control and management, from the simple control loops in TCP and OSPF to the more complicated emergent behaviors of BGP dynamics and overlay routing. From these examples we extract several lessons relevant to ongoing research in autonomic network management.

Human Data Interaction: Historical Lessons from Social Studies and CSCW

Human Data Interaction (HDI) is an emerging field of research that seeks to support end-users in the day-to-day management of their personal digital data. This is a programmatic paper that seeks to elaborate foundational challenges that face HDI from an interactional perspective. It is rooted in and reflects foundational lessons from social studies of science that have had a formative impact on CSCW, and core challenges involved in supporting interaction/collaboration from within the field of CSCW itself. These are drawn upon to elaborate the inherently social and relational character of data and the challenges this poses for the ongoing development of HDI, particularly with respect to the ‘articulation’ of personal data. Our aim in doing this is not to present solutions to the challenges of HDI but to articulate core problems that confront this fledgling field as it moves from nascent concept to find a place in the interactional milieu of everyday life and particular research challenges that accompany it.