Proper Framework for the Application of Power Management Algorithms

A power aware system can reduce its energy dissipation by dynamically powering off during idle periods and powering on again upon a new service request arrival. We minimize the dissipated energy, by selecting the optimal waiting interval before powering off, under consideration of the expected time of the next arrival. This approach has been already proposed in the past, using the idle times distribution, rather than the interarrival periods captured at the moment of service completion. Algorithms proposed in the literature utilize the history of idle periods or assume a vanishing service time. There has been no clear proposition on how service time affects the time instance of our power off decision; rather, whenever service time has been significant, a “blurred” image of the system’s characteristic and a corresponding approximated optimal policy occurred. We clearly show analytically and experimentally that the idle times distribution should not be used as a primary design input, since it is the product of two separate inputs; the interarrival times and the service times. We give insight to our problem, using a mechanical equivalent established at the moment of service completion of all pending requests and show through analytical examples how service time affects our power-off decision. We explain the paradox of being advantageous to wait for intervals more than the shutdown threshold (which is a system characteristic) and show how the introduction of idle period lengths instead of interarrival periods “blurs” the input distribution, leading to non-optimal decisions. Our contribution is to define and solve the proper problem, solely relying on the interarrival distribution. Further, we examine the problem under the framework of competitive analysis. We show how the interarrival distribution that maximizes the competitive ratio, being an exponential distribution, intervenes with power management; it renders the optimization procedure worthless through its “memoryless property”. Exponential interarrivals, irrespective of the service time pattern, are the marginal case where we cannot obtain energy gains. In all other cases the framework we promote ensures considerable advantages compared to other approaches in the literature. Moreover, it leads to a self contained module, implementable in software or hardware, which is based on an iterative formula and thus reduces power management calculations significantly. Here we exploit all operational features of the problem in proposing an implementation which spreads computations over the whole of the waiting period. We extensively compare our results numerically both against claimed expectations and against previous proposals. The outcome fully supports our framework as the one most appropriate for the application of power management.Part of this work has been supported by the EU IST-2001-34157 project PACKWOMAN (Power Aware Communication for Wireless Optimised Personal Area Networks).     

ATM performance evaluation under transparencies of a distributedsystem environment (DSE)

Management architectures as well as protocols for accessing managed entities and exchanging management information are well developed in standards. On the other hand developments in open distributed processing (ODP) are of recognized importance for network and service management. Their generic features fit well into the geographically extended, multiple vendor and heterogeneous environment of communication networks. As a third ongoing development asynchronous transfer mode (ATM) broadband integrated services digital networks (B-ISDN) offer challenging problems for resource allocation, network performance and quality of service (QoS) evaluation in real time. The paper shows how performance monitoring and evaluation for ATM networks can greatly profit from the features of a distributed system environment (DSE). The extreme flexibility offered by the ATM principle requires a rich and reusable set of servers accomplishing coordinated performance evaluation tests. DSE transparencies are an excellent match to corresponding management applications (MA) requirements, so that tests can be performed in a distributed, flexible and adaptable way under a conceptually simple architecture. The paper draws extensively from a non-distributed counterpart, i.e. an existing sophisticated ATM test and analysis tool developed under the “Research for Advanced Communications in Europe” (RACE) program, R1083 PARASOL project     

Management traffic in emerging remote configuration mechanisms for residential gateways and home devices

XML technology is penetrating the network management in the IETF, UPnP, and DSL forum suite of standards and protocols. The advantages of XML are offered at the cost of long byte streams due to XML's inherently verbose nature. The increase in packet size for remote configuration and management can pose problems, if executed in a point-to-multipoint arrangement comprising one automatic configuration server and thousands of home gateways and multimedia devices. We investigate and exploit the repetitive nature of text patterns in typical XML documents as produced by the configuration and management tasks and as coded in SOAP RPCs. The solution mainly comes from application of the Lempel-Ziv compression algorithm, with minimal additions in the proposed DSL Forum standard. Numerical and experimental results support the applicability and advantages of the proposed approach and provide insight on how these are attributable to different layers of the employed protocol stack.     

Development of plastic bottles resistant to lateral deformation

Plastic bottles are sensitive to lateral wall deformation (panelling) owing to the pressure difference between the inside and the outside. Parameters involved in plastic bottle deformation have been reviewed. A quick laboratory test for measuring bottle resistance to deformation was set up and evaluated vs. real life conditions. Round 1–l bottles with various geometries and wall thickness distributions were designed, produced and tested.     

A chaperone in the HSP70 family controls production of extracellular fibrils in Myxococcus xanthus

Three independent Tn5-lac insertions in the S1 locus of Myxococcus xanthus inactivate the sglK gene, which is nonessential for growth but required for social motility and multicellular development. The sequence of sglK reveals that it encodes a homologue of the chaperone HSP70 (DnaK). The sglK gene is cotranscribed with the upstream grpS gene, which encodes a GrpE homologue. Unlike sglK, grpS is not required for social motility or development. Wild-type M. xanthus is encased in extracellular polysaccharide filaments associated with the multimeric fibrillin protein. Mutations in sglK inhibit cell cohesion, the binding of Congo red, and the synthesis or secretion of fibrillin, indicating that sglK mutants do not make fibrils. The fibR gene, located immediately upstream of the grpS-sglK operon, encodes a product which is predicted to have a sequence similar to those of the repressors of alginate biosynthesis in Pseudomonas aeruginosa and Pseudomonas putida. Inactivation of fibR leads to the overproduction of fibrillin, suggesting that M. xanthus fibril production and Pseudomonas alginate production are regulated in analogous ways. M. xanthus and Pseudomonas exopolysaccharides may play similar roles in a mechanism of social motility conserved in these gram-negative bacteria.     

A computationally efficient iterative solution of themultidestination optimal dynamic routing problem

The dynamic routing problem for multiple destination networks is considered. The minimum time rather than total delay cost functional is employed. The problem is solved through an iterative link-by-link optimization. Each link capacity is optimally partitioned by examining the upper bounds for the evacuation time imposed through different capacity allocations for each origin/destination pair traffic. The computational complexity per iteration is polynomial in the number of network nodes. This is due to the examination of origin/destination pairs rather then destinations alone as in previous work where a similar approach led to exponential complexity. Sufficient conditions for the convergence of the iterative algorithm to the optimum are given. If these are not satisfied supplementary steps are described which conduct the algorithm to the desired solution. These involve exponential computational complexity     

Performance evaluation of adaptation functions in the ATMenvironment

The paper models and evaluates key design issues for the adaptation layer in ATM networks. The role and efficient design of the adaptation layer is crucial for future B-ISDN based on ATM. We concentrate on packet-mode adaptation services analyzing and simulating relevant protocols employed for narrowband ISDN signaling and packet data. Processing and transmission resources are modeled. In particular we investigate the performance of software based solution resident in microprocessors and interfaces to the ATM world via a generic interface component. This set-up which is currently under development is found adequate to handle narrowband ISDN signaling and data traffic. It offers a cost effective and readily-available solution for the transition phase towards fully customized broadband components