Which of the following is a metric NOT monitored by web probes?

Network throughput is not a metric monitored by web probes. Web probes focus on specific performance metrics related to the user experience when accessing web content. These include metrics such as Page Fetch Time, which captures how long it takes to load a webpage, DNS Time, which reflects the duration it takes to resolve a domain name, and Server Response Time, which measures how quickly a server responds to a request.

In contrast, network throughput refers to the overall rate of successful data transfer over a network and is generally monitored through different network performance metrics rather than web probes specifically designed for web application performance. Web probes are more focused on the end-user experience and the specific interaction with web applications, while network throughput monitoring often involves more comprehensive tools that assess data flow across the entire network infrastructure.