2716023
An Extended Fault-Tolerant Link-State Routing Protocol in the Internet
Link-state routing protocols, such as OSPF and IS-IS, are widely used in the Internet today. In link-state routing protocols, global network topology information is first collected at each node. A shortest path tree (SPT) is then constructed by applying Dijkstra's shortest path algorithm at each node. Link-state protocols usually require the flooding of new information to the entire (sub)network after changes in any link state (including link faults). Narvaez et al. proposed a fault-tolerant link-state routing protocol without flooding. The idea is to construct a shortest restoration path for each unidirectional link fault. Faulty link information is distributed only to the nodes in the restoration path and only one restoration path is constructed. It is shown that this approach is loop-free. However, the Narvaez et al. approach is inefficient when a link failure is bidirectional because a restoration path is unidirectional and routing tables of nodes in the path are partially updated. In addition, two restoration paths may be generated for each bidirectional link fault. In this paper, we extend the Narvaez et al. protocol to efficiently handle a bidirectional link fault by making the restoration path bidirectional. Several desirable properties of the proposed extended routing protocol are also explored. A simulation study is conducted to compare the traditional link-state protocol, the source-tree protocol, the Narvaez et al. unidirectional restoration path protocol, and the proposed bidirectional restoration path protocol.
17371165
QoS Routing in Hypercube Multicomputers
In this paper, we present a coding method to capture QoS information in hypercube multicomputers. The coding method is based on a localized algorithm where each node interacts with its neighbors to gather QoS information. Specifically, each node maintains a QoS vector where the k-th element represents the guaranteed QoS performance to a destination that is k hops away. The localized algorithm exhibits desirable properties of self-stabilizing, self-optimizing, and self-healing. Simulation results show that this coding method provides a good approximation of the minimum QoS value to a k-hop destination and, at the same time, uses a relatively small number of packets to propagate a change in link state (QoS value) compared with the classical distributed Bellman-Ford method.
2254959
Local-Safety-Information-Based Broadcasting in Hypercube Multicomputers with Node and Link Faults
This paper presents a method to cope with fault-tolerant broadcasting in hypercube multicomputers with both node and link faults. The local safety concept is extended to faulty hypercubes with both node and link faults. The local-safety-based algorithm is used in a fully unsafe hypercube, where there is no safe node. A fully unsafe hypercube can be split into a set of maximal safe subcubes. We show that if these maximal safe subcubes meet certain requirements given in the paper, broadcasting can still be carried out successfully and in some case optimal broadcast is still possible. The method is extended to fault-tolerant routing and multicasting when the system contains both node and link faults.
7582647
On self-similarity and hamiltonicity of dual-cubes
The dual-cube is a newly proposed topology for interconnection networks, which uses low dimensional hypercubes as building blocks. The primary advantages of the dual-cube over the hypercube are that, with the same node degree n, the dual-cube contains 2/sup n-1/ times more nodes than the hypercube and, with the same amount of nodes, the dual-cube has approximately 50% less links than the hypercube. This paper was focused on the investigations of the structural self-similarity and the Hamiltonian property of the dual-cube. It was shown that a dual-cube can be recursively constructed from lower dimensional dual-cubes and, conversely, a dual-cube can be recursively decomposed into lower dimensional dual-cubes. It was also proved that all dual-cubes are Hamiltonian. There exist multiple Hamiltonian cycles on a dual-cube, among which, [(n-1)/2] cycles are edge-disjoint. It was illustrated that rings and linear arrays can be effectively emulated on dual-cubes. Some strategies for track sharing in efficient VLSI layout design were also discussed.
27746153
Broadcasting in Faulty Cube-Connected-Cycles with Minimum Recovery Time
We propose a broadcasting algorithm for a faulty Cube-Connected-Cycles multiprocessor. The broadcasting algorithm delivers a message to all the nodes non-redundantly using a binomial tree. The traffic generated because of the recovery is guaranteed to be minimum.
16257632
XYZ: a scalable, partially centralized lookup service for large-scale peer-to-peer systems
Peer-to-peer (P2P) systems are characterized by direct access between peer computers, rather than through a centralized server. File sharing is the dominant P2P application on the Internet, allowing users to easily contribute, search and obtain content. P2P systems can be categorized by the degrees of centralization. For fully centralized systems, the lookup service will not be available when the central directory server is down. For purely decentralized and unstructured systems, since there is no information about which nodes are likely to have the relevant files, searching essentially amounts to random search. This makes the lookup service unscalable and unpredictable. The objective of this paper is to design a partially centralized, scalable and self-organizing lookup service (XYZ) for wide area P2P systems. A clustering method is used to create the system backbone by connecting the cluster heads together and a color clustering method is adopted to create color overlays and minimize the searching space. Simulations and analysis are also provided. Extensions are proposed to achieve better performance
8704620
Improving the reliability of the label distribution protocol
The LDP (label distribution protocol) is used in the control plane to control an optical network. The data plane and the control plane of an optical network could be physically separate. So a failure in the control plane does not necessarily imply a data plane failure and that user communications have to be interrupted. The standard LDP, however, does not provide any mechanism to recover the knowledge stored in LDP entities about the status of the data plane after the faults are fixed. This is a reliability problem of LDP and results in the unnecessary degradation of user communications. On the other hand, in MPLS-enabled IP networks, being able to recover LDP sessions would be potentially faster and more scalable than to re-establish all affected LSPs. The proposed recovery method of LDP for the control plane failures uses label information mirrors (LIMs) in upstream downstream label switching routers (LSRs). Each LIM is a copy of the label information database (LID) in the LSR of an LDP session. We propose a systematic approach to synchronize the contents of a LIM and the corresponding LID, and show how a LIM is used to handle a control plane failure. Detailed descriptions of the recovery procedure for both control channel failures and control node failures are presented. Some significant features of the proposal are outlined.
59008197
A cycle-based rerouting scheme for wavelength-routed WDM networks
In this paper, we propose a cycle-based rerouting scheme (CRS) for link restoration in wavelength-routed WDM networks. The CRS is based on a scalable set of Pcycles covering a mesh network. Instead of using these Pcycles as enhanced self-healing rings as in traditional approaches, the CRS decomposes these P-cycles into rerouting paths for the links that the P-cycles cover. In this way, flexible and cost-effective link restoration is achieved. Simulation results show that the rerouting performance of the CRS can be very close to the theoretical upper bound.
32095656
Analyzing Outliers Cautiously
Outliers are difficult to handle because some of them can be measurement errors, while others may represent phenomena of interest, something "significant" from the viewpoint of the application domain. Statistical and computational methods have been proposed to detect outliers, but further analysis of outliers requires much relevant domain knowledge. In our previous work (1994), we suggested a knowledge-based method for distinguishing between the measurement errors and phenomena of interest by modeling "real measurements" - how measurements should be distributed in an application domain. In this paper, we make this distinction by modeling measurement errors instead. This is a cautious approach to outlier analysis, which has been successfully applied to a medical problem and may find interesting applications in other domains such as science, engineering, finance, and economics.
6832021
Multiresolution Image Registration Based on Kullback-Leibler Distance
This paper extends our prior work on multi-modal image registration based on the a priori knowledge of the joint intensity dis- tribution that we expect to obtain, and Kullback-Leibler distance. This expected joint distribution can be estimated from pre-aligned training images. Experimental results show that, as compared with the Mutual Information and Approximate Maximum Likelihood based registration methods, the new method has longer capture range at different image resolutions, which can lead to a more robust image registration method. Moreover, with a simple interpolation algorithm based on non-grid point random sampling, the proposed method can avoid interpolation artifacts at the low resolution registration. Finally, it is experimentally demon- strated that our method is applicable to a variety of imaging modalities.
18802972
A diagnostic fault simulator for fast diagnosis of bridge faults
A new diagnostic fault simulator is described that diagnoses both feedback and non-feedback bridge faults while using information from fault simulation of single stuck-at faults. A realistic fault model is used which considers the existence of the Byzantine Generals Problem. The approach has been demonstrated for two-line bridge faults on several large combinational benchmark circuits and has achieved over 98% accuracy for non-feedback bridge faults and over 80% accuracy for feedback bridge faults with good diagnostic resolution.