Dear Filip et al,

I would greatly appreciate your clarification on a few points:

  1. What could explain this discrepancy? Is it a measurement issue or something related to RIPE’s internal systems?

Probes try to maintain a permanent connection to the infrastructure; both ends (and many middle boxes...) can have influence over this. We can have maintenance / outage events on the infra side, affecting the otherwise stable connection of multiple probes at the same time. The significant ones are usually mentioned on the status page: status.ripe.net

Disconnected probes keep on measuring and report later once they are able to.
 
  1. Are all measurements potentially affected by this? For example, measurement 10310, during an outage in NMK on May 18, some probes showed no responses for a 30-minute window(possibly still timing out). Similarly, during the outage in Portugal on April 28, several probes had no data for multiple hours.

    In general when probes are powered up, they are measuring. As said earlier, reporting may happen later. Spain+Portugal had a well-known power outage on April 28, most probes were unfortunately really-really down.
     
    1. How trustworthy are the results from the measurements?

    All probes run similar code to well-known networking tools such as ping, traceroute and dig (implemented in the firmware running on them). The results can be trusted - but on our scale there are always outliers because of local network conditions, misbehaving middle boxes, perhaps bugs, corner cases or manual interference.
     
    1. How long does it typically take for RIPE to detect and reflect a disconnected probe (or other events) in the API?

    During normal operations most events, including connections and disconnection are handled in near real-time. Result reporting for periodic measurements from probes happens every 60-90 seconds (plus the overhead it takes for those to go through the processing pipes until they are retrievable).
     
    1. Different requests to root measurements take the same time, even though one is requesting 30 minutes and another is requesting 4 minutes of data. Is the overhead on Ripe's side the reason for this?

    The built-in measurements run on all probes, so we have to be conscious of the volume of data collected, therefore some of these are running with a lower frequency. 

    I hope this helps,
    Robert