2500739
Efficient construction of multibit tries for IP lookup
Srinivasan and Varghese (1999) have proposed the use of multibit tries to represent routing tables used for Internet (IP) address lookups. They propose dynamic programming algorithms to determine the strides of optimal multibit fixed-stride and variable-stride tries. We improve on these algorithms by providing alternative dynamic programming formulations for both fixed-and variable-stride tries. While the asymptotic complexities of our algorithms are the same as those for the corresponding algorithms of Srinivasan and Varghese, experiments using real IPv4 routing table data indicate that our algorithms run considerably faster. Our fixed-stride trie algorithm is two to four times faster on a SUN workstation and 1.5 to three times faster on a Pentium IV PC. On a SUN workstation, our variable-stride trie algorithm is between two and 17 times faster than the corresponding algorithm of Srinivasan and Varghese; on a Pentium IV PC, our algorithm is between three and 47 times faster. An added feature of our variable-stride trie algorithm is the ability to insert and delete prefixes taking a fraction of the time needed to construct an optimal variable-stride trie "from scratch."
42190976
Efficient Dynamic Lookup For Bursty Access Patterns
Internet (IP) packet forwarding is typically done by finding the longest prefix in a router table that matches the packet's destination address. Although significant effort has been devoted to the development of data structures for static and dynamic router-tables for random packet-access-patterns, considerably less effort has been expended in the development of such structures for bursty access-patterns (i.e., streams of packets in which destination addresses repeat frequently within localized windows of packets). In this paper, we first formulate a variant, ACRBT (alternative collection of red-black trees), of the CRBT (collection of red-black trees) data structure proposed earlier for dynamic router-tables. By replacing the red-black trees used in the ACRBT with splay trees, we obtain the CST (collection of splay trees) structure in which search, insert, and delete take O(log n) amortized time per operation, where n is the number of prefixes in the router table. By replacing the front end of the CST with biased skip lists, we obtain the BSLPT (biased skip lists with prefix trees) structure in which search, insert, and delete take O(log n) expected time. The CST and BSLPT structures are designed so as to perform much better when the access pattern is bursty than when it is not. Experimental results using real IPv4 routing databases and synthetically generated search sequences as well as trace sequences are presented. For extremely bursty access patterns, the CST structure is best. Otherwise, the ACRBT is recommended. Our experiments also indicate that a supernode implementation of the ACRBT usually has better search performance than does the traditional one-element-per-node implementation.
26299662
A Resilient Multipath Routing Protocol for Wireless Sensor Networks
Wireless sensor networks should be self-configuring, highly scalable, redundant, and robust in dealing with shifting topologies due to node failure and environment changes. The energy of a sensor node is the most important system resource, and one of the best ways of conserving energy is to distribute the routing load across all sensor nodes as much equally as possible. Considering the load balance for conserving energy, multipath routing protocols have been employed in sensor networks. In this paper we present a resilient multipath routing protocol based on AODV, named as RMRP, for wireless sensor networks. RMRP is an AODV-based multipath routing protocol in which sensor nodes setup double routing paths toward sink nodes in an AODV fashion and select one of them randomly for forwarding a packet. RMRP proposes a resilient route maintenance scheme which repairs broken links by utilizing localized information around neighbor nodes of the broken link, thereby reducing the flooding range of control messages. To show the effectiveness of the proposed route maintenance scheme, we evaluate the performance enhancement of the proposed scheme by ns2-based simulation.
6524269
Real-time foreground-background segmentation using codebook model
We present a real-time algorithm for foreground-background segmentation. Sample background values at each pixel are quantized into codebooks which represent a compressed form of background model for a long image sequence. This allows us to capture structural background variation due to periodic-like motion over a long period of time under limited memory. The codebook representation is efficient in memory and speed compared with other background modeling techniques. Our method can handle scenes containing moving backgrounds or illumination variations, and it achieves robust detection for different types of videos. We compared our method with other multimode modeling techniques. In addition to the basic algorithm, two features improving the algorithm are presented-layered modeling/detection and adaptive codebook updating. For performance evaluation, we have applied perturbation detection rate analysis to four background subtraction algorithms and two videos of different types of scenes.
838252
Background modeling and subtraction by codebook construction
We present a new fast algorithm for background modeling and subtraction. Sample background values at each pixel are quantized into codebooks which represent a compressed form of background model for a long image sequence. This allows us to capture structural background variation due to periodic-like motion over a long period of time under limited memory. Our method can handle scenes containing moving backgrounds or illumination variations (shadows and highlights), and it achieves robust detection for compressed videos. We compared our method with other multimode modeling techniques.
1602753
Interactive mosaic generation for video navigation
Navigation through large multimedia collections that include videos and images still remains cumbersome. In this paper, we introduce a novel method to visualize and navigate through the collection by creating a mosaic image that visually represents the compilation. This image is generated by a labeling-based layout algorithm using various sizes of sample tile images from the collection. Each tile represents both the photographs and video files representing scenes selected by matching algorithms. This generated mosaic image provides a new way for thematic video and visually summarizes the videos. Users can generate these mosaics with some predefined themes and layouts, or base it on the results of their queries. Our approach supports automatic generation of these layouts by using meta-information such as color, time-line and existence of faces or manually generated annotated information from existing systems (e.g., the Family Video Archive).
5861630
Mobility Agent Advertisement Mechanism for Supporting Mobile IP in Ad Hoc Networks
Mobile IP has been proposed to solve the problem of how a mobile node may roam from its network and still maintain connectivity to the internet. Another emerging wireless architecture, mobile ad hoc networks (MANET), can be flexibly deployed in most environments without the need for infrastructure base stations. Integrating Mobile IP and MANET will facilitate the current trend of moving to an all-IP wireless environment. In this paper we propose an architecture of integrating Mobile IP and MANET based on the on-demand routing protocols. The proposed architecture employs two agent advertisement mechanisms, Mobility Agent Advertisement Mechanism (MAAM) and Aggregation-based Mobility Agent Advertisement Mechanism (AMAAM). In both mechanisms the mobility agent uses periodic beaconing of agent advertisement messages with on-demand routing protocols. Despite its architectural advantage, MAAM has some performance issues to be tackled because it incurs excessive generation of registration request messages of mobile nodes. AMAAM is an enhancement of MAAM for reducing the overhead of the beaconing by aggregating the reply messages of the agent advertisement. The simulation results show that AMAAM can effectively reduce the overhead of periodic agent advertisement and registration process.