I think a large part of your problem is that you’re using trace route to try and determine the full topology of a large complex network. It won’t show the full topology.
On Mon, Jan 17, 2022 at 7:43 PM PAUL R BARFORD <p...@cs.wisc.edu> wrote: > What we're considering specifically are consecutive (layer 3) hops as > identified by traceroute. Thus, TTL is decremented by 1 and no more than 1 > (i.e., we have to get full information (not *****) from consecutive hops to > consider the link). I have asked my colleague to put together a set of > examples. We assume that there are multiple layer 1 and 2 links, and > possibly layer 3 hops masked from traceroute by MPLS. But what we're > seeing in terms of hops exposed by traceroute make it look like a single > (TTL decremented by 1) hop. > > I'll post the examples when I get them. > > PB > ------------------------------ > *From:* morrowc.li...@gmail.com <morrowc.li...@gmail.com> > *Sent:* Monday, January 17, 2022 5:13 PM > *To:* PAUL R BARFORD <p...@cs.wisc.edu> > *Cc:* Pengxiong Zhu <pzhu...@ucr.edu>; nanog@nanog.org <nanog@nanog.org> > > *Subject:* Re: Long hops on international paths > > > > On Mon, Jan 17, 2022 at 5:31 PM PAUL R BARFORD <p...@cs.wisc.edu> wrote: > > Dear Pengxiong, > > Thanks for your questions: > > > 1. We are using CAIDA’s Internet Topology Data Kit (ITDK) that uses > the MIDAR alias resolution method to infer IP addresses assigned to the > same router. > 2. We understand the concerns about IP geolocation. Interfaces of the > router in question are assigned similar domain names e.g., “ > chi-b2-link.ip.twelve99.net” (62.115.50.61). We also used CAIDA’s > ITDK, which provides geolocation information, and indicates that this > router is located in Chicago. We cross-reference with Maxmind where > possible. In this particular case, there is the telltale in the use of > "chi" in the domain name. > 3. > > > I think nick's point about ttl expiry and missing some context on > topology still stands. > I'd be that the paths between 2 continents do not actually land in > chicago... that you're seeing (or not seeing) missing hops between the > coast(s) and chicago inside 1299's network in the US. > > > > 1. > > Hope that helps. > > Regards, PB > ------------------------------ > *From:* Pengxiong Zhu <pzhu...@ucr.edu> > *Sent:* Monday, January 17, 2022 3:23 PM > *To:* PAUL R BARFORD <p...@cs.wisc.edu> > *Cc:* nanog@nanog.org <nanog@nanog.org> > *Subject:* Re: Long hops on international paths > > 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. > > > Pengxiong > > On Mon, Jan 17, 2022 at 10:03 AM PAUL R BARFORD <p...@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 > > -- > > Regards, > Pengxiong Zhu > Department of Computer Science and Engineering > University of California, Riverside > >
