Research On Methods Of Topology Orchestrating And Multipath Generating For Overlay Multipath Transmission

The real-time conversational service is sensitive of the bi-directional network transmission performance.In order to achieve satisfying "quality of experience" of this kind of service,the strict end-to-end guarantee of transmission "quality of service" is required.While in fact that the transmission mechanism of most networks in the Internet is store-and-forward and single path,based on which the end-to-end transmission is vulnerable of random network congestion and failure,and redundant transmission resources could not be exploited.Therefore the multipath transmission methodology has been put forward to optimize transmission performance and its advantages include efficient resource aggregation and robustness.Further,the key factor impacting multipath transmission performance is the method of organizing and scheduling redundant transmission resource in the bearing network.Correspondingly detailed research issues include the architecture of topology orchestrating and the method of multipath generating,which are the research focuses of this dissertation.The realization of multipath transmission in this dissertation is to establish end-to-end multiple relay paths on application-layer overlay network.The contents and innovations of this dissertation consist of the following four parts.(1)The architecture Software-Defined Service Overlay Network(SDSON)is proposed to achieve efficient management of transmission resources and global optimal forwarding control on overlay networks.Nodes and links on overlay networks are controllable transmission resources,and the software-defined networking paradigm is introduced to manage and control them and we name the architecture SDSON.The nodes with forwarding and control functions are respectively divided into forwarding and control planes,and interfaces are defined within each plane and between planes.The control plane achieves global management and control with the global topology resource view,which is generated with two steps.First the control plane builds measure relations based on balanced binary tree and issues them to related forwarding nodes.Then it generates the coordinate-based view with measure results reported from nodes using MDS-MAP.Simulation experiments show that SDSON works effectively,the view matchs well with practical topology and raises small relative error.(2)The multi-dimension topology awareness method is proposed to improve the topology match accuracy between overlay and bearing networks.Topology mismatch would result in performance degradation of multipath transmission,e.g.,unsatisfying delay constrain due to excessive packet detour,ineffective relayed forwarding and resource waste due to loops in bearing network.Network positioning is an effective topology awareness method,nevertheless,coexisting autonomous systems in existing bearing network are relatively independent and enclosed,which leads to positioning accuracy reduction thanks to selection difference of reference nodes.Therefore,the bearing network is divided into two dimensions,namely horizontal and vertical dimensions.In the horizontal dimension,independent topology view is generated for each autonomous system.In the vertical dimension,these views are merged by embedding exchange exports,which are deduced between overlay nodes according to delay and geographic information.Simulation experiments show that multi-dimension view improves positioning accuracy and deduction accuracy is higher under relaxation condition.(3)The two-level distributed architecture with collaborative control for control plane is proposed to enhance scalability performance.The centralized control plane of SDSON would become the performance bottleneck when surging massive requests could not be timely processed.After analyzing and comparing message quantity,it is the forwarding control process that brings more surging load to control plane rather than topology management process.Therefore,the management and control functions in control plane are decoupled and assigned to first and second control planes respectively.The former has the authority of global management and control,but it focuses on global topology management.The latter focuses on forwarding control.The forwarding plane is partitioned into distributed subdomains,which are assigned corresponding second level controllers.These controllers are in charge of management and control of local subdomains,and form the second level control plane,and they employ the collaborative control mechanism to complete global forwarding control.The modified ISODATA algorithm is adopted for subdomain partition,and the algorithm is improved with an initial center prediction method based on node density,and is constrained with practical controller performance.Simulation experiments show that the subdomain partition achieves good clustering results,and the two-level distributed control plane responses efficiently to surging requests,and control loads are effectively alleviated to second control plane.(4)The spatial geometric multipath generating method based on multi-dimension view is proposed to enhance path diversity of end-to-end multiple overlay paths.Path diversity contributes to improving the aggregation of path performance and the tolerance of random network congestion and failure.On the basis of the feature that multiple autonomous systems(AS)coexist in bearing network,overlay paths are categorized into complete-AS path and hybrid path,and end-to-end multiple paths are combination of the two categories.In order to exploit and convert the diversity of bearing network to path diversity,the diversity of bearing network is classified into AS-granularity diversity and link-granularity diversity.In the process of end-to-end multipath generating based on multi-dimension view,the processes of path generating under two different granularities proceed alternatively.When exploiting AS-granularity diversity,the higher independence of different AS facilitates the less correlation of links in different AS,When links belong to uncertain AS,the spatial geometric mechanisms are exploited to reduce link correlation,e.g.,"link deviation angle" characterizes link difference.In addition,the mechanisms constrain multipath generating to reduce complexity and facilitate convergence,e.g.,"transmission direction" determines overlay transmission convergence and "transmission surface" constrains available candidate nodes and avoids loops in bearing networks.Simulation experiments show that the multi-dimension spatial method achieves high path diversity and the stable aggregating rate indirectly indicates the tolerance of random congestion due to high path diversity.