Long hops on international paths

Pengxiong Zhu pzhu011 at ucr.edu
Mon Jan 17 21:23:03 UTC 2022

Hi Paul,

Just curious. How do you determine they are the same routers? Is it based
on IP address or MAC addresses? Or using CAIDA’s router alias database?

Also how do you draw the conclusion that the AS1299 router is indeed in
Chicago? IP-geolocation based on rDNS is not always accurate though.


On Mon, Jan 17, 2022 at 10:03 AM PAUL R BARFORD <pb at cs.wisc.edu> wrote:

> Hello,
> I am a researcher at the University of Wisconsin.  My colleagues at
> Northwestern University and I are studying international Internet
> connectivity and would appreciate your perspective on a recent finding.
> We're using traceroute data from CAIDA's Ark project for our work.  We've observed
> that many international links (i.e., a single hop on an end-to-end path
> that connects two countries where end points on the hop are identified via
> rDNS) tend to originate/terminate at the same routers.  Said another way,
> we are observing a relatively small set of routers in different countries
> tend to have a majority of the international connections - this is
> especially the case for hops that terminate in the US.  For example,
> there is a router operated by Telia (AS1299) in Chicago that has a high
> concentration of such links.  We were a bit surprised by this finding since
> even though it makes sense that the set of providers is relatively small
> (i.e., those that offer global connectivity), we assumed that the set of
> routers that used for international connectivity within any one country
> would tend to be more widely distributed (at least with respect to how they
> appear in traceroute data - MPLS notwithstanding).
> We're interested in whether or not this is indeed standard practice and if
> so, the cost/benefit for configuring international connectivity in this
> way?
> Any thoughts or insights you might have would be greatly appreciated -
> off-list responses are welcome.
> Thank you.
> Regards, PB
> Paul Barford
> University of Wisconsin - Madison
> --

Pengxiong Zhu
Department of Computer Science and Engineering
University of California, Riverside
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