5,625 research outputs found
System Support for Bandwidth Management and Content Adaptation in Internet Applications
This paper describes the implementation and evaluation of an operating system
module, the Congestion Manager (CM), which provides integrated network flow
management and exports a convenient programming interface that allows
applications to be notified of, and adapt to, changing network conditions. We
describe the API by which applications interface with the CM, and the
architectural considerations that factored into the design. To evaluate the
architecture and API, we describe our implementations of TCP; a streaming
layered audio/video application; and an interactive audio application using the
CM, and show that they achieve adaptive behavior without incurring much
end-system overhead. All flows including TCP benefit from the sharing of
congestion information, and applications are able to incorporate new
functionality such as congestion control and adaptive behavior.Comment: 14 pages, appeared in OSDI 200
Building an Emulation Environment for Cyber Security Analyses of Complex Networked Systems
Computer networks are undergoing a phenomenal growth, driven by the rapidly
increasing number of nodes constituting the networks. At the same time, the
number of security threats on Internet and intranet networks is constantly
growing, and the testing and experimentation of cyber defense solutions
requires the availability of separate, test environments that best emulate the
complexity of a real system. Such environments support the deployment and
monitoring of complex mission-driven network scenarios, thus enabling the study
of cyber defense strategies under real and controllable traffic and attack
scenarios. In this paper, we propose a methodology that makes use of a
combination of techniques of network and security assessment, and the use of
cloud technologies to build an emulation environment with adjustable degree of
affinity with respect to actual reference networks or planned systems. As a
byproduct, starting from a specific study case, we collected a dataset
consisting of complete network traces comprising benign and malicious traffic,
which is feature-rich and publicly available
CamFlow: Managed Data-sharing for Cloud Services
A model of cloud services is emerging whereby a few trusted providers manage
the underlying hardware and communications whereas many companies build on this
infrastructure to offer higher level, cloud-hosted PaaS services and/or SaaS
applications. From the start, strong isolation between cloud tenants was seen
to be of paramount importance, provided first by virtual machines (VM) and
later by containers, which share the operating system (OS) kernel. Increasingly
it is the case that applications also require facilities to effect isolation
and protection of data managed by those applications. They also require
flexible data sharing with other applications, often across the traditional
cloud-isolation boundaries; for example, when government provides many related
services for its citizens on a common platform. Similar considerations apply to
the end-users of applications. But in particular, the incorporation of cloud
services within `Internet of Things' architectures is driving the requirements
for both protection and cross-application data sharing.
These concerns relate to the management of data. Traditional access control
is application and principal/role specific, applied at policy enforcement
points, after which there is no subsequent control over where data flows; a
crucial issue once data has left its owner's control by cloud-hosted
applications and within cloud-services. Information Flow Control (IFC), in
addition, offers system-wide, end-to-end, flow control based on the properties
of the data. We discuss the potential of cloud-deployed IFC for enforcing
owners' dataflow policy with regard to protection and sharing, as well as
safeguarding against malicious or buggy software. In addition, the audit log
associated with IFC provides transparency, giving configurable system-wide
visibility over data flows. [...]Comment: 14 pages, 8 figure
Integration of generic operating systems in partitioned architectures
Tese de mestrado, Engenharia Informática (Arquitectura, Sistemas e Redes de Computadores), Universidade de Lisboa, Faculdade de Ciências, 2009The Integrated Modular Avionics (IMA) specification defines a partitioned environment hosting multiple avionics functions of different criticalities on a shared computing platform. ARINC 653, one of the specifications related to the IMA concept, defines a standard interface between the software applications and the underlying operating system. Both these specifications come from the world of civil aviation, but they are getting interest from space industry partners, who have identified common requirements to those of aeronautic applications. Within the scope of this interest, the AIR architecture was defined, under a contract from the European Space Agency (ESA). AIR provides temporal and spatial segregation, and foresees the use of different operating systems in each partition. Temporal segregation is achieved through the fixed cyclic scheduling of computing resources to partitions. The present work extends the foreseen partition operating system (POS) heterogeneity to generic non-real-time operating systems. This was motivated by documented difficulties in porting applications to RTOSs, and by the notion that proper integration of a non-real-time POS will not compromise the timeliness of critical real-time functions. For this purpose, Linux is used as a case study. An embedded variant of Linux is built and evaluated regarding its adequacy as a POS in the AIR architecture. To guarantee safe integration, a solution based on the Linux paravirtualization interface, paravirt-ops, is proposed. In the course of these activities, the AIR architecture definition was also subject to improvements. The most significant one, motivated by the intended increased POS heterogeneity, was the introduction of a new component, the AIR Partition OS Adaptation Layer (PAL). The AIR PAL provides greater POS-independence to the major components of the AIR architecture, easing their independent certification efforts. Other improvements provide enhanced timeliness mechanisms, such as mode-based schedules and process deadline violation monitoring.A especificação Integrated Modular Avionics (IMA) define um ambiente compartimentado com funções de aviónica de diferentes criticalidades a coexistir numa plataforma computacional. A especificação relacionada ARINC 653 define uma interface padrão entre as aplicações e o sistema operativo subjacente. Ambas as especificações provêm do mundo da aviónica, mas estão a ganhar o interesse de parceiros da indústria espacial, que identificaram requisitos em comum entre as aplicações aeronáuticas e espaciais. No âmbito deste interesse, foi definida a arquitectura AIR, sob contrato da Agência Espacial Europeia (ESA). Esta arquitectura fornece segregação temporale espacial, e prevê o uso de diferentes sistemas operativos em cada partição. A segregação temporal é obtida através do escalonamento fixo e cíclico dos recursos às partições. Este trabalho estende a heterogeneidade prevista entre os sistemas operativos das partições (POS). Tal foi motivado pelas dificuldades documentadas em portar aplicações para sistemas operativos de tempo-real, e pela noção de que a integração apropriada de um POS não-tempo-real não comprometerá a pontualidade das funções críticas de tempo-real. Para este efeito, o Linux foi utilizado como caso de estudo. Uma variante embedida de Linux é construída e avaliada quanto à sua adequação como POS na arquitectura AIR. Para garantir uma integração segura, é proposta uma solução baseada na interface de paravirtualização do Linux, paravirt-ops. No decurso destas actividades, foram também feitas melhorias à definição da arquitectura AIR. O mais significante, motivado pelo pretendido aumento da heterogeneidade entre POSs, foi a introdução de um novo componente, AIR Partition OS Adaptation Layer (PAL). Este componente proporciona aos principais componentes da arquitectura AIR maior independência face ao POS, facilitando os esforços para a sua certificação independente. Outros melhoramentos fornecem mecanismos avançados de pontualidade, como mode-based schedules e monitorização de incumprimento de metas temporais de processos.ESA/ITI - European Space Agency Innovation Triangular Initiative (through ESTEC Contract 21217/07/NL/CB-Project AIR-II) and FCT - Fundação para a Ciência e Tecnologia (through the Multiannual Funding Programme
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