Faithful reproduction of network experiments

The proliferation of cloud computing has compelled the research community to rethink fundamental aspects of network systems and architectures. However, the tools commonly used to evaluate new ideas have not kept abreast of the latest developments. Common simulation and emulation frameworks fail to provide scalability, fidelity, reproducibility and execute unmodified code, all at the same time. We present SELENA, a Xen-based network emulation framework that offers fully reproducible experiments via its automation interface and supports the use of unmodified guest operating systems. This allows out-of-the-box compatibility with common applications and OS components, such as network stacks and filesystems. In order to faithfully emulate faster and larger networks, SELENA adopts the technique of time-dilation and transparently slows down the passage of time for guest operating systems. This technique effectively virtualizes the availability of host’s hardware resources and allows the replication of scenarios with increased I/O and computational demands. Users can directly control the tradeoff between fidelity and running-times via intuitive tuning knobs. We evaluate the ability of SELENA to faithfully replicate the behaviour of real systems and compare it against existing popular experimentation platforms. Our results suggest that SELENA can accurately model networks with aggregate link speeds of 44 Gbps or more, while improving by four times the execution time in comparison to ns3 and exhibits near-linear scaling properties.This is the author accepted manuscript. The final version is available from ACM via http://dx.doi.org/10.1145/2658260.265827

Home Network Management Policies: Putting the User in the Loop.

Home networks are becoming increasingly complex but existing management solutions are not simple to use since they are not tailored to the needs of typical home-users. In this paper we present a new approach to home network management that allows users to formulate quite sophisticated comic-strip policies using an attractive iPad application. The policies are based on the management wishes of home users elicited in a user study. Comic-strip policies are passed to a Policy engine running on a new Home Network Router designed to facilitate a variety of management tasks. We illustrate our approach via a number end-to-end experiments in an actual home deployment, using our prototype implementation. © 2012 IEEE

An Information Plane Architecture Supporting Home Network Management

Home networks have evolved to become small-scale versions of enterprise networks. The tools for visualizing and managing such networks are primitive and continue to require networked systems expertise on the part of the home user. As a result, non-expert home users must manually manage non-obvious aspects of the network - e.g., MAC address filtering, network masks, and firewall rules, using these primitive tools. The Homework information plane architecture uses stream database concepts to generate derived events from streams of raw events. This supports a variety of visualization and monitoring techniques, and also enables construction of a closed-loop, policy-based management system. This paper describes the information plane architecture and its associated policy-based management infrastructure. Exemplar visualization and closed-loop management applications enabled by the resulting system (tuned to the skills of non-expert home users) are discussed. © 2011 IEEE.Accepted versio

Inhibition of Mitochondrial Respiration as a Source of Adaphostin-induced Reactive Oxygen Species and Cytotoxicity

Adaphostin is a dihydroquinone derivative that is undergoing extensive preclinical testing as a potential anticancer drug. Previous studies have suggested that the generation of reactive oxygen species (ROS) plays a critical role in the cytotoxicity of this agent. In this study, we investigated the source of these ROS. Consistent with the known chemical properties of dihydroquinones, adaphostin simultaneously underwent oxidation to the corresponding quinone and generated ROS under aqueous conditions. Interestingly, however, this quinone was not detected in intact cells. Instead, high performance liquid chromatography demonstrated that adaphostin was concentrated by up to 300-fold in cells relative to the extracellular medium and that the highest concentration of adaphostin (3000-fold over extracellular concentrations) was detected in mitochondria. Consistent with a mitochondrial site for adaphostin action, adaphostin-induced ROS production was diminished by >75% in MOLT-4 rho(0) cells, which lack mitochondrial electron transport, relative to parental MOLT-4 cells. In addition, inhibition of oxygen consumption was observed when intact cells were treated with adaphostin. Loading of isolated mitochondria to equivalent adaphostin concentrations caused inhibition of uncoupled oxygen consumption in mitochondria incubated with the complex I substrates pyruvate and malate or the complex II substrate succinate. Further analysis demonstrated that adaphostin had no effect on pyruvate or succinate dehydrogenase activity. Instead, adaphostin inhibited reduced decylubiquinone-induced cytochrome c reduction, identifying complex III as the site of inhibition by this agent. Moreover, adaphostin enhanced the production of ROS by succinate-charged mitochondria. Collectively, these observations demonstrate that mitochondrial respiration rather than direct redox cycling of the hydroquinone moiety is a source of adaphostin-induced ROS and identify complex III as a potential target for antineoplastic agents

Conditional Genetic Elimination of Hepatocyte Growth Factor in Mice Compromises Liver Regeneration after Partial Hepatectomy

Hepatocyte growth factor (HGF) has been shown to be indispensable for liver regeneration because it serves as a main mitogenic stimulus driving hepatocytes toward proliferation. We hypothesized that ablating HGF in adult mice would have a negative effect on the ability of hepatocytes to regenerate. Deletion of the HGF gene was achieved by inducing systemic recombination in mice lacking exon 5 of HGF and carrying the Mx1-cre or Cre-ERT transgene. Analysis of liver genomic DNA from animals 10 days after treatment showed that a majority (70-80%) of alleles underwent cre-induced genetic recombination. Intriguingly, however, analysis by RT-PCR showed the continued presence of both unrecombined and recombined forms of HGF mRNA after treatment. Separation of liver cell populations into hepatocytes and non-parenchymal cells showed equal recombination of genomic HGF in both cell types. The presence of the unrecombined form of HGF mRNA persisted in the liver in significant amounts even after partial hepatectomy (PH), which correlated with insignificant changes in HGF protein and hepatocyte proliferation. The amount of HGF produced by stellate cells in culture was indirectly proportional to the concentration of HGF, suggesting that a decrease in HGF may induce de novo synthesis of HGF from cells with residual unrecombined alleles. Carbon tetrachloride (CCl4)-induced regeneration resulted in a substantial decrease in preexisting HGF mRNA and protein, and subsequent PH led to a delayed regenerative response. Thus, HGF mRNA persists in the liver even after genetic recombination affecting most cells; however, PH subsequent to CCl4 treatment is associated with a decrease in both HGF mRNA and protein and results in compromised liver regeneration, validating an important role of this mitogen in hepatic growth. © 2013 Nejak-Bowen et al

Policies for self tuning home networks.

A home network (HN) is usually managed by a user who does not possess knowledge and skills required to perform management tasks. When abnormalities are detected, it is desirable to let the network tune itself under the direction of certain policies. However, self tuning tasks usually require coordination between several network components and most of the network management policies can only specify local tasks. In this paper, we propose a state machine based policy framework to address the problem of fault and performance management in the context of HN. Policies can be specified for complex management tasks as global state machines which incorporate global system behaviour monitoring and reactions. We demonstrate the policy framework through a case study in which policies are specified for dynamic selection of frequency channel in order to improve wireless link quality in the presence of RF interference

A Configuration Service for Home Networks

Accepted versio