550326
Efficient alarm management in optical networks
As the capacity of optical transport networks increases, rapid fault identification and localization become increasingly important. These problems are more challenging than in traditional electronic networks because of optical transparency. In a transparent optical network which does not regenerate optical signals, a fault may propagate to various parts of the network from the origin, and multiple alarms can be generated for a single failure. Efficient alarm management and filtering requires a careful selection and placement of network monitoring equipment. In this paper we survey the capabilities of current optical monitoring equipment and formulate a problem of selecting monitors to be placed throughout the network. Simulation results suggest that the number of monitors and generated alarms can be significantly reduced if monitor locations are selected judiciously.
35661638
Double-Link Failure Recovery in WDM Optical Torus Networks
Most existing link protection methods have been focused on single-link failures. Recently, the double-link failure model has also been considered. In this model, any two links may fail in an arbitrary order. However, an existing model for protecting the entire network against double-link failures does not always provide a 100% recovery when the link identification is not required for pre-computing backup paths. In this paper, we consider double-link failure models that provide 100% recovery in WDM torus optical networks. Three link protection methods are presented. The first method requires failed link identification, whereas the last two methods do not. Other performance measures such as hop-length and backup capacity are also discussed. Finally, we briefly address how our method is possibly extended to mesh optical networks.
800618
Packet filtering for congestion control under DoS attacks
Congestion control in IP networks is typically done at each router through queue management, and the network is entirely dependent on the end hosts to react congestion. However, when misbehaving flows exist and continue to send their packets in very high rates, the queue management schemes implemented in current IP routers reveal a significant shortcoming in protecting legitimate flows. Here, we propose a novel scheme for congestion control in IP networks. Our approach is a time-window based filtering mechanism implemented in a router and processed before a queue management policy is applied. Setting the window size properly and dropping packets reaching in the next window can catch the nonresponsive nature of misbehaving flows. The performance of our proposed scheme is demonstrated through extensive simulations using the NS2, simulator using a set of simulated traffic generated based on IP traces reported in http://www.nlnar.org.
17536274
On double-link failure recovery in WDM optical networks
Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We consider a failure model in which any two links in the network may fail in an arbitrary order. Three loopback methods of recovering from double-link failures are presented. The first two methods require the identification of the failed links, while the third one does not. However, precomputing the backup paths for the third method is more difficult than for the first two. A heuristic algorithm that pre-computes backup paths for links is presented. Numerical results comparing the performance of our algorithm with other approaches suggests that it is possible to achieve 100% recovery from double-link failures with a modest increase in backup capacity.
6488428
Preserving survivability during logical topology reconfiguration in WDM ring networks
We consider the design of reconfiguring logical topologies over physical WDM ring networks. The logical topology consists of the same set of nodes as the physical topology, and the links of the logical topology are lightpaths established (or embedded) over the physical topology. The logical topology is said survivable if the failure of any single physical link does not disconnect the logical topology. In this paper, we consider the following problem: Given a logical topology with its survivable embedding over a physical ring network and a new logical topology to be reconfigured, find a sequence of lightpaths additions and deletions satisfying the given wavelengths and ports constraints such that the logical topology remains survivable throughout the reconfiguration.
386520
Establishing Pair-Wise Keys in Heterogeneous Sensor Networks
Many applications that make use of sensor networks require secure communication. Because asymmetric-key solutions are difficult to implement in such a resource-constrained environment, symmetric-key methods coupled with a priori key distribution schemes have been proposed to achieve the goals of data secrecy and integrity. These approaches typically assume that all sensors are similar in terms of capabilities, and hence deploy the same number of keys in all sensors in a network to provide the aforementioned protections. In this paper we demonstrate that a probabilistic unbalanced distribution of keys throughout the network that leverages the existence of a small percentage of more capable sensor nodes can not only provide an equal level of security but also reduce the consequences of node compromise. We demonstrate the effectiveness of this approach on small networks using a variety of trust models and then demonstrate the application of this method to very large systems. The approach and analysis presented in this paper can be applied to all protocols that use probabilistic keys including those that employ broadcast mechanisms, hash functions or polynomials for the generation of keys.
11704041
Rational parametrization of canal surface by 4 dimensional Minkowski Pythagorean hodograph curves
Lorentzian geometry with a Minkowski Pythagorean hodograph (MPH) formalism in R/sup 3,1/ gives us a new and insightful method of rational parametrization of canal surfaces. Our previous works about MPH curves in R/sup 3,1/ shows that a curve /spl gamma/(t)=(x(t),y(t),z(t),r(t)) in R/sup 3,1/ can be represented by the PH representation map in Cl(3,1) which avoids the complex root finding algorithm. Our parametrization method gives us the flexibility to represent the canal surfaces within their fiber ambiguities. This paper constitutes the first step of our ongoing work which deals with the issues for canal surfaces in a truly new and intriguing manner such as finding rotation minimizing frames. We believe this is just the tip of the iceberg and the further work will yield many valuable applications in the area of canal surfaces.
9897452
Facial feature extraction using PCA and wavelet multi-resolution images
This work presents an algorithm for the extraction of the facial feature (eyebrow, eye, nose and mouth) fields from 2-D gray-level face images. The fundamental philosophy is that eigenfeatures, derived from the eigenvalues and eigenvectors of the gray-level data set constructed from the feature fields, are very useful to locate these fields efficiently. In addition, multi-resolution images, derived from a 2-D DWT (Discrete Wavelet Transform), are used to save the search time of the facial features. The experimental results indicate that the proposed algorithm is robust against facial feature size and slight variations of pose.
5939692
Analyzing the Performance of Mesh and Fat-Tree Topologies for Network on Chip Design
The demand of integration of many heterogeneous semiconductor intellectual property (IP) blocks has been introducing a new chip design paradigm so called on chip network. This paradigm promisingly offers a packet switched network among IPs to reduce the main problems in the very deep sub micron technologies that arise from non-scalable global wire delay, failure to achieve global synchronization, errors due to the signal integrity, non-scalable bus based functional interconnection, etc. This paper introduces interconnected or switched network topologies and also analyze their performances in terms of communication protocol related to the issues such as routing strategy, buffer size, routing algorithm , etc. The above mentioned evaluations are done by utilizing the tool that has been widely used in the research domain of computer network design, so called NS-2.
1950897
Secure reporting of traffic forwarding activity in mobile ad hoc networks
Nodes forward data on behalf of each other in mobile ad hoc networks. In a civilian application, nodes are assumed to be selfish and rational, i.e., they pursue their own self-interest. Hence, the ability to accurately measure traffic forwarding is critical to ensure proper network operation. These measurements are often used to credit nodes based on their level of participation, or to detect loss. Past solutions employ neighbor monitoring and reporting on node forwarding traffic. These methods are not applicable in civilian networks where neighbor nodes lack the desire or ability to perform the monitoring function. Such environments occur frequently in which neighbor hosts are resource constrained, or in networks where directional antennas are used and reliable monitoring is difficult or impossible. In this paper, we propose a protocol that uses nodes on the data path to securely produce packet forwarding reports. Reporting nodes are chosen randomly and secretly so that malicious nodes cannot modify their behavior based upon the monitoring point. The integrity and authenticity of reports are preserved through the use of secure link layer acknowledgments and monitoring reports. The robustness of the reporting mechanism is strengthened by forwarding the report to multiple destinations (source and destination). We explore the security, cost, and accuracy of our protocol.