Risk-Aware Provisioning for Optical WDM Mesh Networks

Abstract

A service-level agreement (SLA) typically specifies, among other metrics, the availability a service provider (SP) promises to a customer. In an optical wavelength division multiplexing (WDM) network, connection-oriented provisioning is commonly based on whether the path's statistical availability complies with the SLA-requested availability. Because of the stochastic nature of network failures, the actually provisioned availability over a specific time period is subject to uncertainty, and hence the SLA is usually at risk. We consider this uncertainty and study provisioning to minimize SLA violations. We show that the SLA Violation Risk is affected by a number of factors (e.g., failure profiles, availability target, and penalty period), and hence cannot simply be characterized by statistical path availability. We formulate the problem of risk-aware provisioning in WDM mesh networks, where path selection is dictated by SLA Violation Risk. In particular, we focus on devising an efficient scheme capable of computing path(s) that are likely to successfully accommodate the SLA-requested availability. A novel technique is applied to convert links with heterogeneous failure profiles to reference links that capture the main risk features in a relative manner. Based on the "reference link" concept, our Risk-Aware Provisioning scheme uses only limited failure information. We also extend our Risk-Aware Provisioning to use shared-path protection (SPP) for connections with strict availability requirements. We evaluate the performance and demonstrate the effectiveness of our schemes in terms of SLA violation ratio compared to the generic availability-aware approaches.

Assessing the risk of violating SLA dependability requirements in software-defined networks

“…addition, we assume that the customer has signed a single SLA with the service provider 3 . In the first step, we count the number of customer's flows that can be delivered to the intended destinations at time t, which is reflected by the n c (t) function as follows:…”

“…To ensure that the services are delivered at the required levels with respect to dependability, ISPs constantly monitor their networks and respond to all events affecting the performance of their services [1], [2]. As part of this task, they also try to estimate the risk of violation of the dependability requirements specified in Service Level Agreements (SLAs) signed with their customers to prepare and deploy adequate protection measures on time, thus avoiding major service disruption and the related penalty [3]- [5]. Each violation of the dependability-related Service Level Objectives (SLOs) defined in the corresponding SLA may lead to significant monetary consequences, affecting the ISP's reputation.…”

“…The currently used metrics in SLAs mainly refer to service downtime which has not been explicitly defined in the case of SDNs. The existing proposals cover non-SDN networks in which an ICT service is either available or not [3]- [5], [14]. At the same time, in SDNs, traffic flows established before a failure may still be successfully forwarded through a network, while the new flows between the same pair of nodes may be rejected due to the unavailability of the logicallycentralized controller.…”

Effective Risk Assessment in Resilient Communication Networks

“…Another compensation policy is to assume that the penalty is proportional to the downtime [39], i.e., the amount of time when the service is not operational. If the penalty is proportional to this time, this policy can be expressed by the so-called interval unavailability, the fraction of time when the service is not operating [40].…”

Resilient network design: challenges and future directions

“…Typically, different customers are willing to live with different levels of risk that a service level agreement is violated [45]. Consequently, not all need to have the same level of resilience from physical layer networks.…”