8147679
Deploying long-lived and cost-effective hybrid sensor networks
In this paper, we consider the problem of network deployment in hybrid sensor networks, consisting of both resource-rich and resource-impoverished sensor devices. The resource-rich devices, called micro-servers, are more expensive but have significantly greater bandwidth and energy capabilities compared to the low-cost, lowpowered sensors. Such hybrid sensor networks have the potential to support the higher bandwidth communications of broadband sensor networking applications, as
14928068
Traffic engineering for MPLS-based virtual private networks
This paper considers the traffic engineering of MPLS-based Virtual Private Networks (VPNs) with multiple classes of service in an offline and centralised setting. We focus on two main issues. Firstly, we point out that the one label switched path (LSP) per ingress-egress pair constraint can be relaxed for the case of MPLS-based VPNs due to the ease in classifying flows on a per-VPN basis. This allows us to use LSP with finer granularity and thus better load balancing. Secondly, we point out that the single objective traffic engineering formulations proposed in literature address only one particular aspect of the traffic engineering problem. In this paper, we propose a multiobjective traffic engineering problem which takes resource usage, link utilisation and number of LSPs into account. The proposed optimisation problem is NP-complete and involves a large number of variables. We propose an heuristic to solve this problem.
29521519
Linear Broadcast Routing
Abstract In this paper we examine the problem of performing broadcasts in networks where the messages are constrained to follow linear paths. Many high speed networks, where routing is done in specialized hardware, have this characteristic. We show that the general problem is NP-complete but find a polynomial time approximation algorithm which is guaranteed to provide a solution which is within twice the optimal. We also suggest some generalizations of this work and propose several open problems.
14479349
Understanding and verifying distributed algorithms using stratified decomposition
Designers of autonomous distributed algorithms ( i.e., algorithms whose complete input is available before the start of execution) customarily refer to temporal ordering in describing the behavior of their algorithms-statements like “after A, task B is performed.” In the absence of an explicit termination detection for A built into the algorithm such a statement should be puzzling. However, the available proof methodologies do not seem to hinge on such statements. This paper provides firm theoretical ground for such as*Supported by NSF Presidential Young Investigators Award under grant DCR84-51396 and matching funds from IBM Faculty Development Award under grant D840622. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/ or specific permission.
16192278
A distributed location service for reducing query failures in geographic ad hoc routing
Location service support is required for mobile nodes using geographic ad hoc routing. The mobile nodes need location information of destinations for sending data packets. Due to mobility or node failures, queries to the location servers may not always succeed. This paper presents a distributed location service (DLS) that employs dual servers to maintain position information of mobile nodes and to achieve efficient performance. With the scheme, the number of failed queries, including no response and erroneous results, can be reduced. DLS has been implemented and evaluated using the ns2 simulator. The experimental results show that DLS not only improved service availability but also location query latency.
34878054
Improving Data Transmission with Helping Nodes for Geographical Ad Hoc Routing
Ad hoc networks have been extensively deployed in recent years. In such networks, obtaining a high efficiency is difficult to achieve due to mobility. Many routing approaches have been proposed to improve the performance of ad hoc networks, including table-driven and demand-driven routing protocols. Geographic routing provides a suitable solution for large-scale and dynamic networks, and reduces link failure problems during packet routing. In wireless networks, nodes movement may cause a network partition, which hinders both data transmission and information availability within the network. Several schemes have been proposed for resolving the partition problem in wireless ad hoc networks. In general, the previous solutions either relied on the use of mobile devices with known trajectories or introduced additional specific mobile nodes. By contrast, this paper proposes a scheme for overcoming the problem of network partitions using only the available devices in the environment. With the scheme, the source node searches for another mobile node, designated as the helping node, which is able to meet the destination. The selected mobile node then carries the packet toward the destination. If the helping node changes its trajectory before it forwards the packet to the destination node, a hand-off scheme is activated and the data packet is transferred to another mobile node for onward transmission
2239697
Performance of batch-based digital signatures
A digital signature is an important type of authentication in a public-key (or asymmetric) cryptographic system, and it is in wide use. The performance of an Internet server computing digital signatures online is limited by the high cost of modular arithmetic. One simple way to improve the performance of the server is to reduce the number of computed digital signatures by combining a set of documents into a batch in a smart way and signing each batch only once. This reduces the demand on the CPU but requires extra information to be sent to clients. We investigate the performance characteristics of online digital signature batching schemes. We give a semi-Markov model of a gated batch-based digital signature server and its approximate solution. We validate the solutions of the analytical model through both emulation and simulation. Our study shows that significant computational benefits can be obtained from batching without significant increases in the amount of additional information that needs to be sent to the clients.