The main statistics page has links to information about Ark monitors, via monitor-specific pages and also a summary page for all monitors.
The summary page shows graphs comparing aggregate results across all Ark monitors.
Each monitor has its own page which shows information about its last cycle of Ark probes. The graphs all link to a page with a larger version of themselves and more explanatory text. From this page, one can navigate to the next/previous monitor (alphabetically) to compare their statistics.
The information found on the monitor pages includes:
- Time range
The start and end times of the traces in this cycle
- Trace count
The total number of attempted probes to destination hosts
- Traces with responding destinations
The number of traces where the destination host gave a response
ASes with responding destinations
The number of ASes where the destination host gave a response
Prefixes with responding destinations
The number of prefixes where the destination host gave a response
- RTT and path length distributions
Graphs and tables of the distributions of RTT and path length (for traces to responding destinations) over the entire cycle
- Ranges of RTTs at each hop distance
A graph of RTT values versus IP hop distance from the Ark monitor
- Comparison of RTT and geographical distance
Graphs of RTT values versus calculated geographical distance from the Ark monitor
Single graph pages
The pages for a single graph gives a larger (and more detailed) image than on the per-monitor page. In addition, the text explains the purpose and potential interpretation of the given data. Like the per-monitor page, one use the left/right links at the top of the page to navigate to the same view (for example, RTT distribution) from another monitor.
Some of the terms have different meanings in different contexts, so here we clarify how the Ark statistics pages use them.
AS (autonomous system): This is the AS number found by using ASFinder on RouteViews routing table dumps. The percentage of ASes that contain responding destinations is out of all the ASes returned by ASFinder for probe destinations, and not out of all known ASes.
Prefix: This is the longest-match routing prefix found by using ASFinder on RouteViews routing table dumps. The percentage of prefixes that contain responding destinations is out of all the prefixes returned by ASFinder for probe destinations, and not out of all known routing table prefixes.
Unknown (for AS graphs): There are three reasons why an AS number is unknown for a specific hop in a path:
- No response. A probe to that hop did not receive any response.
- Private address. A probe to that hop responded, but with an IP address within a known private range (such as those specified in RFC 1918.
- Couldn't map. A probe to that hop responded with a globally routeable address, but we didn't have enough data to map that address to an origin AS.