On 9/29/21 04:23, PAUL R BARFORD wrote:

Hello,

I am a researcher at the University of Wisconsin. My colleagues at Northwestern University and I are studying submarine cable infrastructure.

Our interest is in identifying submarine links in traceroute measurements. Specifically, for a given end-to-end traceroute measurement, we would like to be able to identify when two hops are separated by a submarine cable. Our initial focus has been on inter-hop latency, which can expose long links. The challenge is that terrestrial long-haul links may have the same or longer link latencies as short submarine links. So, we're interested in whether there may be other features (e.g., persistent congestion, naming conventions in router interfaces, peering details, etc.) or techniques that would indicate submarine links.

Any thoughts or insights you might have would be greatly appreciated - off-list responses are welcome.

Back in the day, when submarine cables were not as rife, it was not uncommon to see things like "FLAG" or "APCN-2" or "SMW-3" in traceroutes. I haven't seen such in a very long time, but likely some operators may still do this.

For traceroutes that cross oceans visibly, e.g., lhr-jfk, mrs-mba, hnd-lax, mru - cdg, e.t.c., you could glean from there. But many operators do not follow any "common norm" to annotate things like this, so YMMV.

You also find some countries that will use a submarine festoon either as a primary or backup route for a terrestrial link. In such cases, the distances may be the same, or even shorter across the festoon, e.g., consider a festoon cable between Cape Town - Durban, vs. a land-based run for the same two points.

Considering how wide-spread submarine links are for both short and long spans, I think folk are simply treating them as any other link, from an operational perspective. You may be able to come up with a semi-automatic mechanism to measure this, but I fear without deliberate and consistent human intervention, the data could get stale very quickly.

Mark.