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.
