To support newly emerging and highly dynamic 5G services, optical metro networks must be capable of provisioning services on the fly. Network function virtualization (NFV) is leveraged to fulfill these dynamic service demands by placing virtual network functions (VNFs) in NFV-capable network nodes and chaining them together (“service chaining”). In addition, new 5G service chains often have bandwidth requirements with subwavelength granularity, making traffic grooming essential for efficient network resource utilization. However, the latency requirement for these services will not allow one to always perform traffic grooming, as grooming operations add non-negligible latency to traffic, and this might lead to poor utilization and high service blocking. Thus, it is important to investigate dynamic solutions to increase network utilization and decrease service blocking. One approach to achieve this goal is to reprovision service chains (SCs) to use network resources as efficiently as possible. Reprovisioning consists of tearing down a service chain and reallocating its resources, typically with the intent to make room for new chains that would be otherwise rejected. While traditional reprovisioning entailed only routing reassignment, reprovisioning of SCs entails both rerouting traffic and/or relocating VNFs, hence originating new research problems. In this paper, we propose new heuristic algorithms to reprovision SCs whenever a service cannot be provisioned. We provide two different approaches to perform reprovisioning, i.e., bandwidth and location. While bandwidth reprovisioning consists of modifying only bandwidth assignment of SCs, location reprovisioning considers the possibility of changing the nodes each SC is mapped to. We also considered two different optical network architectures. Results obtained on realistic network topology and services show that location reprovisioning allows us to achieve up to 28% improvement in terms of the number of SCs we are able to provision in the network.

中文翻译：

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在城域网中重新配置可感知延迟的动态服务链

为了支持新兴的，高度动态的5G服务，光学城域网必须能够即时配置服务。通过将虚拟网络功能（VNF）放在支持NFV的网络节点中并将它们链接在一起（“服务链接”），可以利用网络功能虚拟化（NFV）来满足这些动态服务需求。此外，新的5G服务链通常具有亚波长粒度的带宽要求，因此流量梳理对于有效利用网络资源至关重要。但是，这些服务的延迟要求将不允许人们始终执行流量修饰，因为修饰操作会为流量增加不可忽略的延迟，这可能导致利用率低下和服务阻塞高。从而，研究动态解决方案以提高网络利用率并减少服务阻塞非常重要。实现此目标的一种方法是重新配置服务链（SC），以尽可能高效地使用网络资源。重新配置包括拆除服务链并重新分配其资源，通常是为了为否则会被拒绝的新链条腾出空间。传统的重新配置仅需要路由分配，而SC的重新配置则需要重新路由流量和/或重新定位VNF，因此引发了新的研究问题。在本文中，我们提出了新的启发式算法，以在无法提供服务时重新供应SC。我们提供两种不同的方法来执行重新配置，即带宽和位置。虽然带宽重新分配仅包含修改SC的带宽分配，但是位置重新分配考虑了更改每个SC映射到的节点的可能性。我们还考虑了两种不同的光网络架构。在实际的网络拓扑和服务上获得的结果表明，位置重新配置使我们能够在网络中提供的SC数量方面提高多达28％。