Network virtualization can serve as the important technology for constructing the next-generation Internet architecture. It has been proposed as a powerful vehicle for running multiple architectures or experiments simultaneously on a shared infrastructure. It allows multiple service providers to offer customized end-to-end services over a common physical infrastructure. Virtual network embedding is a critical step for network virtualization that deals with the efficient mapping of virtual nodes and virtual links onto the substrate network resources. The virtual network-mapping problem is extremely challenging for four main practical reasons: Node and link constraints, admission control, online request, and diverse topologies. Due to different application scenarios, optimization objectives, mapping approaches, and constraints, there are many virtual network-mapping models. Unfortunately, the optimization problems of these models are generally NP-hard. The model of virtual network mapping is presented. The virtual network mapping methods and algorithms are concluded. The technological approaches to solve the optimization problems of the virtual network mapping are summarized. Finally, some open issues are presented to be further studied in the virtual network-mapping field.%网络虚拟化被视为构建新一代互联网体系架构的重要技术,它使得能在一个共享的底层物理网络上同时运行多个网络架构或网络应用,从而能为用户提供多样化的端到端定制服务.虚拟网络映射是实现网络虚拟化的关键环节,其目的是在满足虚拟网络资源需求的前提下,将虚拟网络植入到合适的底层物理节点和链路.虚拟网络映射需要解决资源约束、准入控制、在线请求和拓扑多样性等多方面的问题.根据应用场景、优化目标、映射方式和约束条件的不同,可以得到不同类型的虚拟网络映射优化问题.这些优化问题通常是NP难的.通过形式化建立了虚拟网络映射模型,归纳了虚拟网络映射的方法和算法.总结了解决虚拟网络映射模型优化问题的几条技术途径,指出了该领域中需要进一步研究的热点问题.
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