Juno:An adaptive delivery-centric middleware

This paper proposes a new delivery-centric abstraction. A delivery-centric abstraction allows applications to generate content requests agnostic to location or protocol, with the additional ability to stipulate high-level requirements regarding such things as performance, security, resource consumption and monetary cost. A delivery-centric system therefore constantly adapts to fulfil these requirements, given the constraints of the environment. This abstraction has been realised through a delivery-centric middleware called Juno, which uses a reconfigurable software architecture to (i) discover multiple sources of an item of content, (ii) model each source's ability to provide the content, then (iii) adapt to interact with the source(s) that can best fulfil the application's requirements. Juno therefore utilises existing providers in a backwards compatible way, supporting immediate deployment. This paper evaluates Juno using Emulab to validate its ability to adapt to its environment

Coupling of relative intensity noise and pathlength noise to the length measurement in the optical metrology system of LISA Pathfinder

LISA Pathfinder is a technology demonstration mission for the space-based gravitational wave observatory, LISA. It demonstrated that the performance requirements for the interferometric measurement of two test masses in free fall can be met. An important part of the data analysis is to identify the limiting noise sources. [1] This measurement is performed with heterodyne interferometry. The performance of this optical metrology system (OMS) at high frequencies is limited by sensing noise. One such noise source is Relative Intensity Noise (RIN). RIN is a property of the laser, and the photodiode current generated by the interferometer signal contains frequency dependant RIN. From this electric signal the phasemeter calculates the phase change and laser power, and the coupling of RIN into the measurement signal depends on the noise frequency. RIN at DC, at the heterodyne frequency and at two times the heterodyne frequency couples into the phase. Another important noise at high frequencies is path length noise. To reduce the impact this noise is suppressed with a control loop. Path length noise not suppressed will couple directly into the length measurement. The subtraction techniques of both noise sources depend on the phase difference between the reference signal and the measurement signal, and thus on the test mass position. During normal operations we position the test mass at the interferometric zero, which is optimal for noise subtraction purposes. This paper will show results from an in-flight experiment where the test mass position was changed to make the position dependant noise visibl

A trace-driven analysis of caching in content-centric networks

A content-centric network is one which supports host-to-content routing, rather than the host-to-host routing of the existing Internet. This paper investigates the potential of caching data at the router-level in content-centric networks. To achieve this, two measurement sets are combined to gain an understanding of the potential caching benefits of deploying content-centric protocols over the current Internet topology. The first set of measurements is a study of the BitTorrent network, which provides detailed traces of content request patterns. This is then combined with CAIDA’s ITDK Internet traces to replay the content requests over a real-world topology. Using this data, simulations are performed to measure how effective content-centric networking would have been if it were available to these consumers/providers. We find that larger cache sizes (10,000 packets) can create significant reductions in packet path lengths. On average, 2.02 hops are saved through caching (a 20% reduction), whilst also allowing 11% of data requests to be maintained within the requester’s AS. Importantly, we also show that these benefits extend significantly beyond that of edge caching by allowing transit ASes to also reduce traffic

The Survival of the Fittest: An Evolutionary Approach to Deploying Adaptive Functionality in Peer-to-Peer Systems

The heterogeneous, large-scale and decentralised nature of peerto-peer systems creates significant issues when deploying new functionality and adapting peer behaviour. The ability to autonomously deploy new adaptive functionality is therefore highly beneficial. This paper investigates middleware support for evolving and adapting peers in divergent systems through reflective component based design. This approach allows selfcontained functionality to exist in the network as a primary entity. This functionality is autonomously propagated to suitable peers, allowing nodes to be evolved and adapted to their individual constraints and the specific requirements of their environment. This results in effective functionality flourishing whilst suboptimal functionality dies out. By this, a self-managed infrastructure is created that supports the deployment of functionality following the evolutionary theory of natural selection. This approach is evaluated through simulations to highlight the potential of using natural selection for the deployment and management of software evolution

Cooperation in P2P Systems through Sociological Incentive Patterns

While the performance of peer-to-peer (p2p) systems largely depend on the cooperation of the member nodes, there is an inherent conflict between the individuals’ self interest and the communal social welfare. In this regard, many interesting parallels between p2p systems and cooperation in human societies can be drawn. On the one hand, human societies are organized around a certain level of altruistic behavior. Whilst, on the other hand, individuals tend to overuse public goods, if they are free to do so. This paper proposes a new incentive scheme that extracts and modifies sociological incentive patterns, based on the Tragedy of Commons analogy, to work efficiently in a p2p environment. It is shown through simulations that this scheme encourages honest peers whilst successfully blocking non-contributors

Corelli: A Peer-to-Peer Dynamic Replication Service for Supporting Latency-Dependent Content in Community Networks

The quality of service for latency dependent content, such as video streaming, largely depends on the distance and available bandwidth between the consumer and the content. Poor provision of these qualities results in reduced user experience and increased overhead. To alleviate this, many systems operate caching and replication, utilising dedicated resources to move the content closer to the consumer. Latency-dependent content creates particular issues for community networks, which often display the property of strong internal connectivity yet poor external connectivity. However, unlike traditional networks, communities often cannot deploy dedicated infrastructure for both monetary and practical reasons. To address these issues, this paper proposes Corelli, a peer-to-peer replication infrastructure designed for use in community networks. In Corelli, high capacity peers in communities autonomously build a distributed cache to dynamically pre-fetch content early on in its popularity lifecycle. By exploiting the natural proximity of peers in the community, users can gain extremely low latency access to content whilst reducing egress utilisation. Through simulation, it is shown that Corelli considerably increases accessibility and improves performance for latency dependent content. Further, Corelli is shown to offer adaptive and resilient mechanisms that ensure that it can respond to variations in churn, demand and popularity