The availability and reliability of optical backbone links are very important to ensure the efficient operation of the Internet. To address the issue of data loss due to optical link failures, there is a need for an optimal recovery strategy so that the traffic can be rerouted on a backup path to the destination. This paper builds on top of our prior research efforts (Yavary Mehr et al., 2022; Zhou et al., 2017) which introduced the concept of Resource Delayed Release (RDR) by adding a new state called ”idle state” which begins when the channel has completed carrying its services so that the next request can be carried immediately instead of waiting for a new channel to be established. While RDR improves the network performance by reducing the service provisioning time and blocking probability, it does not handle link failures which are quite common in optical networks. Therefore, enhancing RDR with protection strategies will make the network more reliable and thus we investigate this topic in this work.

In this paper, we evaluate four different protection methods for single link failure recovery in WDM networks (Path Protection (PP), Partial Path Protection (PPP), Segment Protection (SegP) and Link Protection (LP)) with two different routing approaches namely Shortest Path (SPath) and Greedy (G) algorithm under uniform and non-uniform traffic generated using real traffic traces collected from a local Internet Service Provider (ISP). Special attention while evaluating these protection strategies was paid to the optimization of the amount of remaining bandwidth. The performance evaluation of the network under uniform and non-uniform traffic was done over the NSFNet and COST239 topologies by employing the metrics of link and network utilization, Blocking Probability (BP), Bandwidth Blocking Probability (BBP), Recovery Time (RT) and Service Provisioning Time (SPT). Our results show that the PPP method performs the best in terms of reducing BP, BBP, and SPT compared with PP, LP, and SegP in all three topologies while utilizing RDR.

光骨干链路的可用性和可靠性对于保证互联网的高效运行非常重要。为了解决由于光链路故障导致的数据丢失问题，需要一种最佳的恢复策略，以便流量可以在备份路径上重新路由到目的地。本文建立在我们之前的研究成果（Yavary Mehr 等人，2022 年；Zhou 等人，2017 年）的基础上，通过添加一个称为“空闲状态”的新状态引入了资源延迟释放（RDR）的概念，该状态开始于该通道已经承载完自己的业务，可以立即承载下一个请求，而不必等待新的通道建立。而RDR则通过减少业务提供时间和阻塞概率来提高网络性能，它不处理光网络中很常见的链路故障。因此，通过保护策略增强 RDR 将使网络更加可靠，因此我们在这项工作中研究了这个主题。

在本文中，我们评估了 WDM 网络中单链路故障恢复的四种不同保护方法（路径保护 (PP)、部分路径保护 (PPP)、分段保护 (SegP) 和链路保护）(LP))，在使用从本地互联网服务提供商 (ISP) 收集的真实流量跟踪生成的均匀和非均匀流量下，使用两种不同的路由方法，即最短路径 (SPath) 和贪婪 (G) 算法。在评估这些保护策略时，特别关注剩余带宽量的优化。通过采用链路和网络利用率、阻塞概率（BP）、带宽阻塞概率（BBP）、恢复时间（RT）和服务提供时间 (SPT)。我们的结果表明，与 PP、LP 和 SegP 相比，在使用 RDR 的所有三种拓扑中，PPP 方法在降低 BP、BBP 和 SPT 方面表现最佳。