It's that business deal I want to hear about. When A-B and B-C are free peering but the traffic goes A-B-C for some reason other than a misconfiguration or deliberate abuse. On or off list, I'd like to know about real-life use cases where folks do this on purpose.
As far as I understand some NRENs do that in Europe. Check out AS1853 and AS-ACONETTOVIX in the RIPE whois. "A" networks are the peers a VIX, "B" is ACONET, "C" networks are CESNET, SANET, and PIONIER. DTAG's looking glass shows this path to SANET: sh ip bgp regexp _2607_ BGP table version is 0, local router ID is 217.239.38.165 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, R Removed Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *>i147.175.0.0 194.25.5.150 100 0 1853 2607 i *>i147.213.0.0 194.25.5.150 100 0 1853 2607 i *>i147.232.0.0 194.25.5.150 100 0 1853 2607 i *>i158.193.0.0 194.25.5.150 100 0 1853 2607 i *>i158.195.0.0 194.25.5.150 100 0 1853 2607 i *>i158.197.0.0 194.25.5.150 100 0 1853 2607 i *>i192.108.130.0 194.25.5.150 100 0 1853 2607 i *>i192.108.131.0 194.25.5.150 100 0 1853 2607 i *>i192.108.132.0/23 194.25.5.150 100 0 1853 2607 i *>i192.108.138.0 194.25.5.150 100 0 1853 2607 i *>i192.108.149.0 194.25.5.150 100 0 1853 2607 i *>i193.87.0.0/16 194.25.5.150 100 0 1853 2607 i *>i194.1.0.0/17 194.25.5.150 100 0 1853 2607 i *>i194.160.0.0/16 194.25.5.150 100 0 1853 2607 i Total number of prefixes 14 Regards, András