共查询到20条相似文献,搜索用时 15 毫秒
1.
In optical grid networks, data files for job execution are replicated at multiple sites in order to distribute loads and achieve
high performance computing. Those replicas are downloaded in parallel in order to reduce downloading time. Furthermore, each
replica is downloaded with multiple wavelengths. Although parallel and multi-wavelength downloading reduce downloading time,
they raise blocking probability of file downloading. This is because they use a lot of wavelength resources and thus often
generate bottleneck links. To resolve this problem, this paper proposes a parallel and multi-wavelength downloading scheme
for optical grid networks. The proposed scheme provides replica selection, route selection, and wavelength selection for parallel
and multi-wavelength downloading. In the proposed scheme, clients dynamically select combinations of a replica, a route, and
a wavelength in such a way that they suppress the generation of bottleneck links. Through simulation experiments, we show
that the proposed scheme efficiently improves blocking probability of parallel and multi-wavelength downloading. 相似文献
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为提高分布式存储系统中文件的获取速度,提出一种尾块动态调整的多节点协作并行下载算法,通过对文件分块下载中的最后一块进行调整使得多个并行下载流尽可能同时结束.对比实验结果表明本文的下载算法提高了下载速度,改善了用户的下载体验. 相似文献
5.
In this paper, we have proposed an efficient wavelength rerouting algorithm for dynamic provisioning of lightpath. In wavelength-division multiplexed (WDM) networks rerouting of lightpath can be used to improve throughput and to reduce blocking probability. We have proposed a Lightpath Rerouting Algorithm (LRRA) for dynamic traffic in WDM optical networks. The results have shown that LRRA can improve blocking performance of the network. In this paper, low complexity algorithm has been developed which is used for the calculation of blocking probability of network. The proposed algorithm has also been applied on the realistic network such as NSFnet for calculation and optimization of blocking probability of the network. The results have also shown that the proposed algorithm can be implemented to huge networks for good blocking performance of the network. 相似文献
6.
In this paper, we have proposed an efficient wavelength rerouting algorithm for dynamic provisioning of lightpath. In wavelength division multiplexed (WDM) networks rerouting of lightpath can be used to improve throughput and to reduce blocking probability. We have proposed a shortest path wavelength rerouting (SPWRR) algorithm for dynamic traffic in WDM optical networks. The results have shown that SPWRR algorithm can improve blocking performance of the network. In this paper, low complexity algorithm has been developed which is used for the calculation of blocking probability of network. The proposed algorithm has also been applied on the realistic network such as NSFnet for calculation and optimization of blocking probability of the network. 相似文献
7.
Miyagi H. Hayashitani M. Ishii D. Arakawa Y. Yamanaka N. 《Lightwave Technology, Journal of》2007,25(10):2904-2910
A deadline-aware-scheduling scheme for the lambda grid system is proposed to support a huge computer grid system based on an advanced photonic network technology. The assignment of wavelengths to jobs in order to efficiently carry various services is critical in lambda grid networks. Such services have different requirements such as the job-completion deadlines, and wavelength assignment must consider the job deadlines. The conventional job scheduling approach assigns a lot of time slots to a call within a short period in order to finish the job as quickly as possible. This raises the blocking probability of short deadline calls. Our proposal assigns wavelengths in the lambda grid networks to meet quality-of-services guarantees. The proposed scheme assigns time slots to a call over time according to its deadline, which allows it to increase the system performance in handling short deadline calls, for example, lowering their blocking probability. Computer simulations show that the proposed scheme can reduce the blocking probability by a factor of 100 compared with the conventional scheme under the low load condition in which the ratio of long deadline calls is high. The proposed scheduling scheme can realize more efficient lambda grid networks. 相似文献
8.
Due to the explosive growth of data-related traffic driven by the Internet, network reliability becomes an important issue. We investigate various protection approaches to handle failures for dynamic traffic demands in IP/MPLS-over-WDM networks. An LSP can be protected at either the IP/MPLS layer or the optical layer. In IP/MPLS layer protection, an LSP is protected by providing a link-disjoint backup LSP between its end nodes. In optical layer protection, an LSP is protected by the backup lightpath of each lightpath traversed by the LSP. We present two integrated routing algorithms: hop-based integrated routing algorithm and bandwidth-based integrated routing algorithm (BIRA) to set up the restorable bandwidth-guaranteed paths efficiently. Then we present a multilayer protection scheme for multiclass traffic in such networks. This scheme takes into account the different QoS and recovery requirements of the traffic to provide protection capability either at the MPLS layer or at the optical layer in a cost-effective manner. We use the connection blocking probability and number of optical-electrical-optical conversions as performance metrics to compare various protection approaches. 相似文献
9.
Internet service providers(ISPs) have taken some measures to reduce intolerable inter-ISP peer-to-peer(P2P) traffic costs,therefore user experiences of various P2P applications have been affected.The recently emerging offline downloading service seeks to improve user experience by using dedicate servers to cache requested files and provide high-speed uploading.However,with rapid increase in user population,the server-side bandwidth resource of offline downloading system is expected to be insufficient in the near future.We propose a novel complementary caching scheme with the goal of mitigating inter-ISP traffic,alleviating the load on servers of Internet applications and enhancing user experience.Both architecture and caching algorithm are presented in this paper.On the one hand,with full knowledge of P2P file sharing system and offline downloading service,the infrastructure of complementary caching is designed to conveniently be deployed and work together with existing platforms.The co-operational mechanisms among different major components are also included.On the other hand,with in-depth understanding of traffic characteristics that are relevant to caching,we develop complementary caching algorithm with respect to the density of requests,the redundancy of file and file size.Since such relevant information can be real-time captured in our design,the proposed policy can be implemented to guide the storage and replacement of caching unities.Based on real-world traces over 3 months,we demonstrate that the complementary caching scheme is capable to achieve the ’three-win’ objective.That is,for P2P downloading,over 50% of traffic is redirected to cache;for offline downloading,the average server-dependence of tasks drops from 0.71 to 0.32;for user experience,the average P2P transfer rate is increased by more than 50 KB/s. 相似文献
10.
In this letter, we propose a computational model for calculating blocking probabilities of multifiber wavelength division multiplexing (WDM) optical networks. We first derive the blocking probability of a fiber based on a Markov chain, from which the blocking probability of a link is derived by means of conditional probabilities. The blocking probability of a lightpath can be computed by a recursive formula. Finally, the network-wide blocking probability can be expressed as the ratio of the total blocked load versus the total offered load. Simulation results for different fiber-wavelength configurations conform closely to the numerical results based on our proposed model, thus demonstrating the feasibility of our proposed model for estimating the blocking performance of multifiber WDM optical networks. 相似文献
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Baccarelli E. Biagi M. Cordeschi N. Pelizzoni C. 《Vehicular Technology, IEEE Transactions on》2009,58(4):1695-1710
In this contribution, we consider emerging wireless content delivery networks (CDNs), where multiple (possibly nomadic) clients download large-size files from battery-powered proxy servers via faded links that are composed of multiple slotted orthogonal bearers (e.g., logical subchannels). Since the considered transmit proxy servers are battery-powered mobile routers, a still open basic question deals with searching for optimal energy-allocation (e.g., energy scheduling) policies that efficiently split the available energy over the (faded) bearers. The target is to minimize the resulting (average) download time when constraints on the average available energy per information unit (IU), peak-energy per slot, and minimum energy per bearer (e.g., rate-induced constraints) are simultaneously active. The performance and the robustness of the resulting optimal energy scheduler are tested on the last hop of Rayleigh-faded mesh networks that adopt the so-called ldquodirty paper strategyrdquo for broadcasting multiple traffic flows that are generated by proxy servers equipped with multiple antennas . 相似文献
13.
Yonggyu Lee Yonghoon Choi Seungjin Lee Jun Kyun Choi 《Photonic Network Communications》2011,21(2):152-157
This article provides a new scheme for the blocking probability evaluation for optical burst switching networks. While several
previous articles used mainly links as servers, we consider switches as servers. In order to evaluate the blocking probability
at switches, we use the effective bandwidth method. The method shows more accurate results and the accuracy of the method
is proven by simulation and numerical analyses. 相似文献
14.
云存储下多用户协同访问控制方案 总被引:1,自引:0,他引:1
CP-ABE被认为是云存储下最适合的数据访问控制方法之一,但它仅适合用户分别读取或者分别修改不同数据的情况,而直接应用CP-ABE进行多用户协同数据访问时,会存在修改无序、密文文件大量冗余等问题。多用户协同访问云端数据时,应该在保证机密性、抗共谋的前提下控制合法用户有序地修改同一密文文件,同时云端尽可能减少密文文件副本。针对文件和文件逻辑分块,提出了2个多用户协同访问控制方案MCA-F和MCA-B。MCA-F满足单个数据文件作为最小控制粒度的访问控制需求,该方案采用层次加密结构,云服务器承担部分解密计算,以降低用户解密的计算代价;针对多用户同时写数据的访问控制,提出了对多个用户提交的暂存数据的管理方法。MCA-B用于文件的逻辑分块作为最小控制粒度的访问控制,该方案设计了文件的逻辑分块机制、基于索引矩阵的表示方法,提出了子数据掩码表示方法以描述多个用户对同一文件不同逻辑分块的写权限;MCA-B支持用户集合、文件逻辑分块结构的动态变化,而且数据的拥有者和修改者无需一直在线。与现有的方案相比,所提方案不仅具有云存储下多用户协同写数据的访问控制能力,而且读访问控制的用户端存储量和加解密计算量是较小的。 相似文献
15.
Sengupta A. Bandyopadhyay S. Balla A. R. Jaekel A. 《Photonic Network Communications》2000,2(2):163-184
In this paper, we have studied a number of algorithms for routing in all-optical wavelength routed networks. We have considered situations where a lightpath is dynamically created in response to a request for communication and the WDM channels constituting the lightpath are reclaimed when the communication is over. We have looked at two schemes for dynamic wavelength allocation. In the first scheme we have assumed the existence of a central agent to maintain a database of existing lightpaths where the central agent attempts to generate a new lightpath in response to a request for communication. In the second scheme, we attempt to generate a new lightpath using a distributed algorithm. In the first scheme we have exploited the existence of multiple paths between any pair of nodes in a network in order to reduce the blocking probability. For the second scheme, we have proposed three distributed strategies to determine, if possible, a lightpath when there is a request for communication. Each of these strategies have their advantages and disadvantages in terms of the expected blocking probability and the set-up time. We have studied the performances of both the schemes using Monte Carlo simulation. 相似文献
16.
Wajdi Halabi Kris Steenhaut Marnix Goossens Thu-Huong Truong Ann Nowé 《Photonic Network Communications》2012,23(3):217-229
Routing, connection setup, and path computation are well-known problems in multi-domain networks, which have been largely
analyzed in pure IP (packet) networks. In circuit-switched optical multi-domain networks, there remain, however, a number
of routing and path computation challenges. Traffic grooming means combining a number of low-speed traffic streams so that
the high capacity of each lightpath may be used as efficiently as possible, as path computation implements the core of the
grooming function, it is obvious that solutions for the traffic grooming problem in optical multi-domain networks are still
not sufficiently investigated. In this study we propose a methodology to address the problems of routing, connection setup,
and traffic grooming in optical multi-domain networks, which adapts a two-level hierarchical routing scheme and full-mesh
topology abstraction algorithm to improve routing scalability and lower inter-domain blocking probabilities; additionally
our proposed methodology adapts a scheme for traffic grooming in DWDM multi-domain networks to improve the resources usage.
To test our proposed methodology we propose a detailed IP/MPLS-based ASON/GMPLS multi-domain multilayer test framework. 相似文献
17.
Yiu-Wing Leung 《Lightwave Technology, Journal of》2006,24(9):3259-3267
In some deployments of all-optical networks, it is necessary to concentrate the lightpaths from some fibers to fewer fibers. An N/spl times/M lightpath concentrator is an optical component for this purpose, and it concentrates the lightpaths from N incoming fibers to M outgoing fibers. In this paper, three designs of N/spl times/M lightpath concentrators are proposed. The first design is a generalization of optical crossconnects, and it requires M/spl times/M optical switches. The second design incorporates the concept of partial concentration so that it requires only m/spl times/m optical switches (where m相似文献
18.
An Efficient Distributed Control Scheme for Lightpath Establishment in Dynamic WDM Networks 总被引:2,自引:0,他引:2
An adaptive hybrid reservation protocol (AHRP) is proposed for the purpose of quickly and efficiently establishing a lightpath in dynamic wavelength routed networks. This protocol uses a special reservation-and-probe (RESV_PROB) packet and extends the signaling to integrate forward reservation and backward reservation into one monolithic process. To decrease the blocking probability that happens in cases where two end nodes associated with a specific link simultaneously reserve the same wavelength, an adaptive wavelength selection policy is specially employed in AHRP. A discrete-event simulation tool based on ns-2 is developed to investigate AHRP's performance, including its blocking probability, average lightpath setup delay, and signaling overhead. AHRP is also compared with existing protocols. Results show that during highly dynamic traffic conditions, AHRP possesses the lowest blocking probability, shorter setup delay, and less signaling overhead. 相似文献
19.
Jae Yoon Chung Sangtae Ha James Won‐Ki Hong 《International Journal of Network Management》2015,25(6):435-453
Cloud service providers offer virtual resources to users, who then pay for as much as they use. High‐speed networks help to overcome the limitation of geographical distances between clients and cloud servers, which encourage users to adopt cloud storage services for data backup and sharing. However, users use only a few cloud storage services because of the complexity of managing multiple accounts and distributing data to store. In this paper, we propose the client‐defined management architecture (CLIMA) that redefines a storage service by coordinating multiple cloud storage services from clients. We address practical issues of coordinating multiple cloud service providers using a client‐based approach. We implement a prototype as a realization of CLIMA, which achieves both reliability and privacy protection using erasure code and higher performance by optimally scheduling data transmission. We use our prototype to evaluate the benefits of CLIMA on commercial cloud storage service providers. Finally, CLIMA empowers clients to increase the manageability and flexibility of cloud storage services. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
In satellite and wireless networks and in advanced traffic information systems in which the up-link bandwidth is very limited, a server broadcasts data files in a round-robin manner. The data files are provided by different providers and are accessed by many clients. The providers are independent and therefore files may share information. The clients who access these files may have different patterns of access. Some clients may wish to access more than one file at a time in any order, some clients may access one file out of of several files, and some clients may wish to access a second file only after accessing another file. The goal of the server is to order the files in a way that minimizes the access time of the clients given some a-priori knowledge of their access patterns. This paper introduces a clients–providers–servers model that better represents certain environments than the traditional clients–servers model. Then, we show that a random order of the data files performs well, independent of the specific access pattern. Our main technical contribution is de-randomizing the procedure that is based on selecting a random order. The resulting algorithm is a polynomial-time deterministic algorithm that finds an order with the same performance bounds as those of the random order. 相似文献