Network Function Virtualization enables network slicing as a novel paradigm for service provisioning. With network slicing, Virtual Network Functions (VNFs) can be instantiated at different locations of the infrastructure, choosing their optimal placement based on parameters such as the requirements of the service or the resources available. One limitation of state-of-the-art technology for network slicing is the inability to re-evaluate orchestration decisions once the slice has been deployed, in case of changing service demands or network conditions.

In this paper, we present ACHO, a novel software framework that enables seamless re-orchestration of VNFs of any kind, including RAN and Core. With ACHO, VNFs and resources can be easily re-assigned to match, e.g., varying user demands or changes in the nodes’ load. ACHO uses lightweight mechanisms, such as splitting the engine of a VNF from the data it requires to perform its operation, in such a way that, when re-allocating a VNF, only the data is moved (a new engine is instantiated in the new location). We demonstrate the use of ACHO in a small scale testbed, showing that (i) the proposed re-orchestration is feasible, (ii) it results much faster than existing alternatives (especially for relocation), and (iii) the framework can be readily applied to existing VNFs after minimal changes to their implementation.

网络功能虚拟化使网络切片成为一种新的服务供应范例。通过网络切片，可以在基础结构的不同位置实例化虚拟网络功能（VNF），并根据诸如服务需求或可用资源之类的参数选择其最佳位置。用于网络切片的最新技术的局限性是，一旦更改了切片，就无法在服务需求或网络条件发生变化的情况下重新评估业务流程决策。

在本文中，我们介绍了ACHO，这是一种新颖的软件框架，可对包括RAN和Core在内的任何类型的VNF进行无缝重新编排。使用ACHO，可以轻松地重新分配VNF和资源以匹配，例如，不断变化的用户需求或节点负载的变化。ACHO使用轻量级机制，例如从执行操作所需的数据中分离出VNF引擎，以便在重新分配VNF时仅移动数据（新引擎在新实例中实例化）。位置）。我们演示了在小型测试平台上使用ACHO的情况，表明（i）提议的重新编排是可行的，（ii）结果比现有替代方案要快得多（尤其是用于重定位），并且（iii），只需对其实现进行最小的更改即可轻松将其应用于现有的VNF。