Thanks to its computational and forwarding capabilities, the mobile network infrastructure can support several third-party (“vertical”) services, each composed of a graph of virtual (network) functions (VNFs). Importantly, one or more VNFs are often common to multiple services, thus the services deployment cost could be reduced by letting the services share the same VNF instance instead of devoting a separate instance to each service. By doing that, however, it is critical that the target KPI (key performance indicators) of all services are met. To this end, we study the VNF sharing problem and make decisions on 1) when sharing VNFs among multiple services is possible, 2) how to adapt the virtual machines running the shared VNFs to the combined load of the assigned services, and 3) how to prioritize the services traffic within shared VNFs. All decisions aim to minimize the cost for the mobile operator, subject to requirements on end-to-end service performance, e.g., total delay. Notably, we show that the aforementioned priorities should be managed dynamically and vary across VNFs. We then propose the FlexShare algorithm to provide near-optimal VNF-sharing and priority assignment decisions in polynomial time. We prove that FlexShare is within a constant factor from the optimum and, using real-world VNF graphs, we show that it consistently outperforms baseline solutions.

中文翻译：

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通过VNF共享降低服务部署成本

由于其计算和转发功能，移动网络基础架构可以支持多个第三方（“垂直”）服务，每个服务都由虚拟（网络）功能（VNF）图组成。重要的是，一个或多个VNF通常是多个服务所共有的，因此可以通过让服务共享同一VNF实例而不是为每个服务分配单独的实例来降低服务部署成本。但是，这样做必须符合所有服务的目标KPI（关键绩效指标）。为此，我们研究了VNF共享问题，并在以下方面做出决策：1）何时可以在多个服务之间共享VNF； 2）如何使运行共享VNF的虚拟机适应分配的服务的组合负载； 3）如何在共享VNF中确定服务流量的优先级。所有决定的目的在于使移动运营商的成本降到最低，这取决于对端到端服务性能的要求，例如总延迟。值得注意的是，我们表明上述优先级应动态管理，并且在VNF之间有所不同。然后，我们提出FlexShare算法，以在多项式时间内提供近乎最佳的VNF共享和优先级分配决策。我们证明FlexShare与最佳值之间处于恒定因素之内，并且使用真实的VNF图，我们证明FlexShare始终优于基准解决方案。