On Tue, Jan 18, 2022 at 6:49 AM PAUL R BARFORD <pb@cs.wisc.edu> wrote:
So, the question is what is the cost/benefit to providers to configure/maintain routes (that include long MPLS tunnels) that tend to concentrate international connectivity at a relatively small number of routers?
Most likely that's not what's happening. None of your traces showed traffic going to Chicago and then doubling back. I can't say with certainty what this means but my educated guess is this: Chicago is a major peering point for the networks in question, so packets headed more or less that direction tend to hop over there instead of somewhere else. Having crossed over, they enter the MPLS system which is opaque to traceroute, so they're not seen again until they exit MPLS. Traffic originating closer to the final destination goes to a scattering of other MPLS entry points instead, so Chicago looks outsized in the data. The actual traffic flow, opaque inside MPLS, goes through the nodes you'd expect, close to the cable landings. So it's not a question of whether the traffic has an international destination, it's a question of whether that backbone is in the path to the destination (international or not). Rephrase your question as: is there a cost/benefit to providers having a small number of very large peering points accepting traffic into their networks in addition to the myriad small ones. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/