17359298
Queueing Network Modeling of Computer Communication Networks
The application of queueing network models to the performance analysis of messageswitched (or packet-switched) commumcatmn networks m surveyed. The main topics covered are the analysis of end-to-end delay and the analysis of buffer management schemes. A brief discussmn on flow control is also included. A queueing network model is developed for a simple user-resource network. The mean response time of a host computer m this network is illustrated by a numerical example.
3873642
On staleness and the delivery of web pages
A popular technique to improve the scalability of a web based system is caching at proxy servers. Caching has the drawback that a cached page becomes stale when the page is updated at the web server. In some cases, staleness may not be completely avoided because the server may not wish to expend the processing and communication resources required to transmit all the updates immediately. In general, if updates are transmitted less frequently, the staleness will tend to increase, but the amount of resources consumed will be reduced. The tradeoff between resource consumption and staleness is investigated. A measure of staleness is defined and optimization problems are formulated. The solutions to these problems allow one to come up with an optimal strategy for transmitting page updates. Numerical examples showing the resource consumption/staleness tradeoff are presented.
969658
Performance Analysis of Secure Web Server Based on SSL
In recent years, protocols have been developed to ensure secure communications over the Internet, e.g., the secure sockets layer (SSL) and secure electronic transaction (SET). Deployment of these protocols incurs additional resource requirements at the client and server. This may have a negative impact on system performance. In this paper, we consider a scenario where users request information pages stored on a web server, and some of the requests require secure communication. An analytic model is developed to study the performance of a web server based on SSL. In our model, the details of the client-server interactions found in a typical SSL session are represented explicitly. Input parameters to this model are obtained by measuring an existing SSL implementation. Numerical examples on the performance characteristics of SSL are presented.
27801438
Scheduling Algorithms for Videotex Systems Under Broadcast Delivery
1948833
Synchronization of Distributed Simulation Using Broadcast Algorithms
Abstract Simulation, particularly of networks of queues, is an application with a high degree of inherent parallelism, and is of considerable practical interest. We continue the analysis of synchronization methods for distributed simulation, defined by the taxonomy in our previous paper. Specifically, we develop algorithms for time-driven simulation using a network of processors. For most of the synchronization methods considered, each node k of an n-node network simulation cannot proceed directly with its part of a simulation. Rather, it must compute some function Bk(ν1, ν2, …, νn), where νi is some value which must be obtained from node i. The value of νi at each node changes as the simulation progresses, and must be broadcast to every other node for the recomputation of the B-functions. In some cases, it is advantageous to compute the B-function in a distributed manner. Broadcast algorithms for such distributed computation are presented. Since the performance of a broadcast algorithm depends on the properties of the inter-process communication facility, we characterize some particular cases and give algorithms for each of them.
21841074
Delay Analysis of Broadcast Routing in Packet-Switching Networks
Broadcast addressing is the capability to send a packet from a source node to all other nodes in the network. Store-and-forward, packet-switching networks are not inherently designed to carry broadcast packets, and broadcasting has to be implemented by some sort of routing algorithm. In this paper, the source based forwarding algorithm is considered. With this algorithm, a spanning tree is defined for each node, and broadcast packets are sent along the branches of these trees. Approximation methods are presented to obtain a lower bound and estimates of the mean broadcast time. The accuracy of these methods is evaluated by comparison with simulation.
18507162
A statistical methodology for wire-length prediction
In this paper, the classic wire-length estimation problem is addressed and a new statistical wire-length estimation approach that captures the probability distribution function of net lengths after placement and before routing is proposed. These types of models are highly instrumental in formalizing a complete and consistent probabilistic approach to design automation and design closure where, along with optimizing the pertinent cost function, the associated prediction error is also considered. The wire-length prediction model was developed using a combination of parametric and nonparametric statistical techniques. The model predicts not only the length of the net using input parameters extracted from the floorplan of a design, but also probability distributions that a net with given characteristics after placement will have a particular length. The model is validated using the learn-and-test and resubstitution techniques. The model can be used for a variety of purposes, including the generation of a large number of statistically sound, and therefore realistic, instances of designs. The net models were applied to the probabilistic buffer-insertion problem and substantial improvement was obtained in net delay after routing (~ 20%) when compared to a traditional bounding box (BBOX)-based buffer-insertion strategy
9656670
Temporal properties of low power wireless links: modeling and implications on multi-hop routing
Recently, several studies have analyzed the statistical properties of low power wireless links in real environments, clearly demonstrating the differences between experimentally observed communication properties and widely used simulation models. However, most of these studies have not performed in depth analysis of the temporal properties of wireless links. These properties have high impact on the performance of routing algorithms.Our first goal is to study the statistical temporal properties of links in low power wireless communications. We study short term temporal issues, like lagged autocorrelation of individual links, lagged correlation of reverse links, and consecutive same path links. We also study long term temporal aspects, gaining insight on the length of time the channel needs to be measured and how often we should update our models.Our second objective is to explore how statistical temporal properties impact routing protocols. We studied one-to-one routing schemes and developed new routing algorithms that consider autocorrelation, and reverse link and consecutive same path link lagged correlations. We have developed two new routing algorithms for the cost link model: (i) a generalized Dijkstra algorithm with centralized execution, and (ii)a localized distributed probabilistic algorithm.
47328768
Effective iterative techniques for fingerprinting design IP
Fingerprinting is an approach that assigns a unique and invisible ID to each sold instance of the intellectual property (IP). One of the key advantages fingerprinting-based intellectual property protection (IPP) has over watermarking-based IPP is the enabling of tracing stolen hardware or software. Fingerprinting schemes have been widely and effectively used to achieve this goal; however, their application domain has been restricted only to static artifacts, such as image and audio, where distinct copies can be obtained easily. In this paper, we propose the first generic fingerprinting technique that can be applied to an arbitrary synthesis (optimization or decision) or compilation problem and, therefore to hardware and software IPs. The key problem with design IP fingerprinting is that there is a need to generate a large number of structurally unique but functionally and timing identical designs. To reduce the cost of generating such distinct copies, we apply iterative optimization in an incremental fashion to solve a fingerprinted instance. Therefore, we leverage on the optimization effort already spent in obtaining previous solutions, yet we generate a uniquely fingerprinted new solution. This generic approach is the basis for developing specific fingerprinting techniques for four important problems in VLSI CAD: partitioning, graph coloring, satisfiability, and standard-cell placement. We demonstrate the effectiveness of the new fingerprinting-based IPP techniques on a number of standard benchmarks.
1015013
Watermarking of SAT using combinatorial isolation lemmas
Watermarking of hardware and software designs is an effective mechanism for intellectual property protection (IPP). Two important criteria for watermarking schemes are credibility and fairness. In this paper, we present the unique solution-based watermarking technique which provides, in a sense, the ultimate answer to both credibility and fairness requirements. Leveraging on a combinatorial theorem of Valiant and Vazirani, we demonstrate how ultimate credibility and complete fairness can almost always be achieved with high probability during the watermarking of the solution of the satisfiability (SAT) problem. The effectiveness of the technique is demonstrated on both specially created examples where the number of solutions is known, as well as on common CAD and operation research SAT instances.
8543519
Design and Implementation of National Engineering Education Delivery System