In some cases, when reporting RUM data, you might notice "NA" or "Unknown" values.
While this might seem like a malfunction, there are scenarios where getting these types of values is unavoidable. For example, some browsers don't support all APIs used for capturing data, so they might not return all the metrics that we can report for more fully-supported modern browsers like Chrome.
For single page apps (SPAs) we report both hard and soft navigations, but hard and soft navigations have different things that can be measured. A soft navigation in a single page app does not load a full HTML file that can be considered the root request of the page, so there will be no values for DNS, SSL, TCP, etc.