2,467 research outputs found
Verifying service continuity in a satellite reconfiguration procedure: application to a satellite
The paper discusses the use of the TURTLE UML profile to model and verify service continuity during dynamic reconfiguration of embedded software, and space-based telecommunication software in particular. TURTLE extends UML class diagrams with composition operators, and activity diagrams with temporal operators. Translating TURTLE to the formal description technique RT-LOTOS gives the profile a formal semantics and makes it possible to reuse verification techniques implemented by the RTL, the RT-LOTOS toolkit developed at LAAS-CNRS. The paper proposes a modeling and formal validation methodology based on TURTLE and RTL, and discusses its application to a payload software application in charge of an embedded packet switch. The paper demonstrates the benefits of using TURTLE to prove service continuity for dynamic reconfiguration of embedded software
RCD: Rapid Close to Deadline Scheduling for Datacenter Networks
Datacenter-based Cloud Computing services provide a flexible, scalable and
yet economical infrastructure to host online services such as multimedia
streaming, email and bulk storage. Many such services perform geo-replication
to provide necessary quality of service and reliability to users resulting in
frequent large inter- datacenter transfers. In order to meet tenant service
level agreements (SLAs), these transfers have to be completed prior to a
deadline. In addition, WAN resources are quite scarce and costly, meaning they
should be fully utilized. Several recently proposed schemes, such as B4,
TEMPUS, and SWAN have focused on improving the utilization of inter-datacenter
transfers through centralized scheduling, however, they fail to provide a
mechanism to guarantee that admitted requests meet their deadlines. Also, in a
recent study, authors propose Amoeba, a system that allows tenants to define
deadlines and guarantees that the specified deadlines are met, however, to
admit new traffic, the proposed system has to modify the allocation of already
admitted transfers. In this paper, we propose Rapid Close to Deadline
Scheduling (RCD), a close to deadline traffic allocation technique that is fast
and efficient. Through simulations, we show that RCD is up to 15 times faster
than Amoeba, provides high link utilization along with deadline guarantees, and
is able to make quick decisions on whether a new request can be fully satisfied
before its deadline.Comment: World Automation Congress (WAC), IEEE, 201
Traffic Engineering in G-MPLS networks with QoS guarantees
In this paper a new Traffic Engineering (TE) scheme to efficiently route sub-wavelength requests with different QoS requirements is proposed for G-MPLS networks. In most previous studies on TE based on dynamic traffic grooming, the objectives were to minimize the rejection probability by respecting the constraints of the optical node architecture, but without considering service differentiation. In practice, some high-priority (HP) connections can instead be characterized by specific constraints on the maximum tolerable end-to-end delay and packet-loss ratio. The proposed solution consists of a distributed two-stage scheme: each time a new request arrives, an on-line dynamic grooming scheme finds a route which fulfills the QoS requirements. If a HP request is blocked at the ingress router, a preemption algorithm is executed locally in order to create room for this traffic. The proposed preemption mechanism minimizes the network disruption, both in term of number of rerouted low-priority connections and new set-up lightpaths, and the signaling complexity. Extensive simulation experiments are performed to demonstrate the efficiency of our scheme
Time Protection: the Missing OS Abstraction
Timing channels enable data leakage that threatens the security of computer
systems, from cloud platforms to smartphones and browsers executing untrusted
third-party code. Preventing unauthorised information flow is a core duty of
the operating system, however, present OSes are unable to prevent timing
channels. We argue that OSes must provide time protection in addition to the
established memory protection. We examine the requirements of time protection,
present a design and its implementation in the seL4 microkernel, and evaluate
its efficacy as well as performance overhead on Arm and x86 processors
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