دانلود رایگان مقاله انگلیسی تعبیه چند هدفه از شبکه های مجازی نرم افزارمحور - الزویر 2018

Abstract

Softwarization is the current trend of networking based on the success of technologies like Software Defined Networking (SDN) and Network Virtualization. Network as a Service (NaaS) is a new paradigm based on virtualization that enables customers to instantiate their virtual networks over a physical substrate network, mapping necessary resources by a Virtual Network Embedding (VNE) algorithm. Each VNE algorithm defines a resource allocation strategy of the NaaS provider, and determines its expenditures and revenues. Even though the problem of VNE has been widely investigated in recent years, virtualization in SDN introduces new challenges due to the new role of the controller and additional architectural constraints. In this paper, we investigate the VNE problem where both virtual and substrate networks are software defined. We propose a mathematical programming formulation that considers both the objectives of the NaaS provider (profit maximization) and the customers (switch-controller delay minimization). Proposing new design metrics (i.e., k-hop delay, correlation, and distance), we develop a heuristic algorithm, and prove its effectiveness through extensive simulations in the well-known VNE evaluation tool, ALEVIN, and comparisons with other algorithms and mathematical bounds.

Impact of design parameters

SVE is a parametric algorithm, where the parameters and influence on the performance of the algorithm. The parameter determines the number of hops which are used to estimate the K-hop delay. In SVE, it is claimed that bounding the number of hops leads to a better estimation of delay, and consequently more suitable location of controller is found that decreases the delay between switches and controllers. This statement is satisfied in Fig. 7 where the average delays of two versions of SVE are depicted. In one version, depicted by dashed lines, the K-hop bounding is used where is determined by (23), while in the second version, depicted by solid line, the K-hop bounding mechanism is removed from the algorithm. As indicated, using the K-hop delay leads to decrease in the switch-controller communication delay. The second parameter is that balances between the profit and the delay. The effect of this parameter is shown in Fig. 8 that depicts the average switch-controller delay by SVE for different values of . By increasing the value of , SVE puts more attention to the delay and tries to map virtual nodes as close as possible to the controller. Increasing the value of causes that SVE does make effort to map virtual nodes alongside each other. Therefore, virtual links are mapped on longer paths that increase the cost and consequently decrease the revenue-to-cost ratio. This effect of on the ratio is shown in Table V.