Issue link: https://www.e-digitaleditions.com/i/1414667
October/November/December 2021 I 25 FIGURE 4: Multi-layer monitoring delivers the full story. LAYERED MONITORING FOR BETTER VISIBILITY For the monitoring of communications networks, there are really two dimensions to consider—network monitoring and service monitoring. Network monitoring typically refers to monitoring performed at link layer 2 which is often Ethernet, the routing layer 3 which is often internet protocol (IP), or the transport layer 4 which is often transmission control protocol (TCP) or user datagram protocol (UDP). Collectively, this monitoring provides key performance indicators (KPIs) that are used to derive quality of service (QoS) metrics, the traditional domain of the NOC. Service monitoring typically involves monitoring at the higher layers (up to layer 7, the application layer) and provides KPIs related to the application performance and customer experience and collectively are referred to QoE metrics, the traditional domain of the SOC (Figure 4). As networks continue to virtualize and data centers, including third-party or public data centers, become a bigger part of the network infrastructure, the traditional role of the NOC becomes less clear with respect to the operator's service delivery. This is one of the reasons why the SOC is taking on a more prominent role in operations. The other reason is that customer QoE has become a more critical aspect of an operator's long-term success because the very nature of virtualized networks and services makes it easier for customers to change providers if they are not satisfied. Leveraging multiple layers of network and service KPIs enable operators to make more intelligent and accurate decisions about both reactively managing customer impacting events as well as proactively man- aging degrading network and service performance before their customers notice any problems. It may not seem obvious how a multi-layered monitoring approach can be applied to a dark optical fiber DCI provider. Again, the virtualized data center provides an answer.