Orion already does this. This has to do with your settings and will do the exact same thing in Orion as in your Cacti chart (although the design will obviously look a bit different. Also, you are comparing a step chart in Orion to a line type chart in Cacti). For Orion to do this you have to make sure the sample intervals are smaller than the amount of downtime commonly experienced by your interfaces. By default most sample intervals on charts are set to 30 minutes. So, only connectivity drops longer than 30 minutes would show in a chart where the sample interval is set to 30 minutes.
Also notice where the Sample Interval entry is it tells you that Data within each Sample Interval is summarized, so if you have a default 30 Minute interval set on y our chart and within that 30 minutes there was 20 minutes of downtime on the interface then Orion will simply summarize the 10 minutes of uptime data it got into that whole 30 minute sample interval and would just show as one point of data. However, if you had the interval set to 5 minutes then you would have 6 points of data in that 30 minute period, 4 of which would be empty and 2 of which that would display data. That would result in missing sections on the resulting chart (depending on how zoomed out the chart is of course) just like your Cacti chart.
So, here is a chart where the intervals are at 1 minute and shows the last week of data. You'll see the spaces where the interface was not up. This is the same as the Cacti chart you displayed just with a different look. Depending on the type of Chart (this is a custom chart) there can be several ways to display it including Line, Area, Step (the one you showed), bar, and several others. Each one will have different characteristics. This is a pretty under utilized interface so it isn't quite as full as your Cacti chart, but all of my highly utilized interfaces don't have any downtime at the moment, so this is the best I can do. Still, the blank areas represent times when the interface was down (in this case it is just a user workstation that is turned on and off frequently).
Thanks,
Jordan Hume
Field Systems Engineer
Loop1 Systems, Inc.