Research On Some Key Problems Of Store-and-forward Optical Circuit Switched Network

The emergence of cloud services,socical media and Mobile Internet is fueling the unprecedented demands for bulk data transfer.Bulk data,generated from datacenter backups,big file transfer,e-Science applications,and the like,are often high volume(GB~TB),bandwidth hungry(more than 1 Gbps).However,the available bandwidth not only varies in time,but also by locations,which makes it difficult to deliver data over end-to-end(E2E)paths across a large-scale network.A typical example is data transfer across multiple time zones.Due to the inconsistency of the variation patterns in different time zones,an E2 E path with high bandwidth across multiple time zones is hard to be realized.Even in the same time zone,since the available bandwidth varies link by link,the transmission window of an E2 E path is still small,and hence cannot meet the requirement of bulk data transfer.Store-and-Forward(SnF)is considered as a promising solution to the aforementioned dilemma.Storage is deployed in network nodes so that the network can perform SnF.In the way,bulk data can be temporarily store at intermediate nodes(e.g.,datacenter)at the peak hours and forwarded when the network is less busy.By performing SnF,bulk flows can efficiently use the leftover bandwidth so as to improve the network performance.Studies indicate that SnF can improve the data delivery capability of networks without incurring additional transfer cost.However,the storage formulates the conventional spatial routing problem into a spatial and temporal scheduling problem.Besides,the inherent phenomena,such as bandwidth fragmentation and detour,escalate when the resources are scheduled inappropriately,which in turn degrades the network performance.Obviously,the use of storage poses challenges on the resource(bandwidth and storage)scheduling.This thesis focuses on Store-and-Forward Optical Circuit Switched(SnF OCS)network,and studies the resource scheduling and related issues.Although the studies in this thesis are based on SnF OCS networks,they are also applicable to any circuit switching or virtual circuit switching networks.Our studies also provide clues to apply SnF to bandwidth-guaranteed packet-switched networks.The details of our work are discussed as follows:1.Research on a routing framework for SnF OCS networksThe main idea of SnF is to efficiently schedule the time-varying bandwidth by using storage.Therefore,how to capture the dynamics of bandwidth and use it for routing requests is a fundamental issue.In this thesis,we propose a routing framework,namely Time-Shifted Multilayer Graph(TS-MLG).This framework is based on a multilayer graph built from a set of snapshots(i.e.,layers)of the dynamics in a network.By performing shortest path routing on the multilayer graph,“end-to-end” paths over time and space are found for requests,thus greatly simplifying the provisioning process.2.Research on the slotted network operation in SnF OCS networksThe dynamics of network contribute to bandwidth gaps.How to efficiently use these gaps determines the network performance.In this thesis,we investigate the applicability of coarser granular slotted network operations in SnF OCS networks.Studies shows that applying larger time slots can provide better blocking and control benefits to the network than using unslotted operations.3.Research on the TSD scheduling method for SnF OCS networksTo further reduce the computational complexity of the resource scheduling method,we propose time-space-decoupling SnF scheduling method.The main idea of TSD method is to decouple the SnF scheduling problem into the spatial routing problem and the temporal scheduling problem.Studies show that TSD method can reduce the computation time while maintaining an acceptable blocking probability,compared to the joint method.4.Design of a high-fault-tolerant and cost-efficient optical switch matrixOptical switch is the core functional component of the SnF OCS network.The reliability of data transfer requires a fault-tolerant optical switch.We propose a cyclic fault-tolerant structure(CFT)for optical switch matrix by connecting the inputs of the switch matrix into a ring.Upon component failures,the affected requests are rerouted through their neighboring inputs toward the desired outputs.Studies show that the CFT structure outperforms the typical fault-tolerant strutures in terms of fault tolerance,scalability and cost.5.Application of SnF OCS in access network and WANIn order to investigate the applicability of SnF OCS in end-to-end transmission scenarios,we apply SnF OCS in an access network and WAN,and propose two methods to solve the pratical problems.The main contributions of this thesis:(1)We propose a routing framework for SnF OCS networks,which greatly simplifies the routing and scheduling process.(2)We apply the slotted network operations in SnF OCS networks.Our studies show that coarser granular slotted operations could benefit the network performance.(3)We propose a TSD scheduling method,which reduces the complexity of SnF scheduling algorithm while maintaining a low request blocking probability.(4)We propose a cyclic fault-tolerant structure for optical matrix,which obtains high fault tolerance while maintaining low cost.(5)We apply SnF OCS in an access network and WAN,and propose solutions for the practical problems.