Ahhh, but that was not the correct question to ask (I have not read the study). It is not whether ISP's filter inbound customer route announcements. It is how they filter them. If the customer goes and says I am going to announce 4.0.0.0/8 and the ISP just blindly adds that to the filter, we have a problem, but the ISP did answer that question truthfully. They are filtering.
That's one important question, but another other question is, are _ALL_ customers prefix filtered? How about major peers? Sure, the default, new, small customer is prefix filtered. In 2000 -- the same year that study was done -- we were adding prefixes so quickly that iHug unfiltered us, and EPOCH unfiltered iHug, to prevent the need for us to notify them of every single route change. At any one time we only had around 150 prefixes maximum - there's just a lot of 203.* space which goes back and forward between ISPs in Australia resulting in a lot of filter updates. _After_ our circuit had been disconnected from iHug, for a brief period long before 66.0.0.0/8 was allocated, I tested pushing the /8 to their BGP peer we had in the US (multihop BGP as it was a satellite service). In theory: 0. Our BGP session should have been shut down anyway, when our satellite service was cancelled 1. Bogon filtering would catch it 2. Anyone using RADB would catch it 3. It wouldn't get far as no major network would pick it up The result - all test sites I tried either saw the route, or default routed to someone who saw the route. Here's an example of the non-optimal route taken from one site, but the fact is it still made it to hop #16, after which it would have gone to us if our satellite PVC was still active, and just from this example AARNet, Optus, UUnet, BBN, EPOCH, Netgate and iHug all in some way would reach that clearly bogus advertisement. Which says to me that at least in 2000, the big guys weren't even applying simple bogon filters on routes received between each other. typhaon; traceroute 66.0.0.1 traceroute to 66.0.0.1 (66.0.0.1), 30 hops max, 40 byte packets 1 muchacho.uwa.edu.au (130.95.128.128) 1.515 ms 0.88 ms 1.702 ms 2 parnet-uwa.parnet.edu.au (203.19.110.17) 2.848 ms 2.664 ms 2.353 ms 3 ATM9-0-0-2.ia5.optus.net.au (192.65.88.189) 57.681 ms 57.819 ms 59.205 ms 4 GigEth12-0-0.rr2.optus.net.au (202.139.191.22) 57.83 ms 57.787 ms 57.658 ms 5 POS5-0-0.la1.optus.net.au (192.65.89.214) 368.02 ms 367.933 ms 368.018 ms 6 34.ATM0-0-0.GW1.LAX4.ALTER.NET (157.130.227.181) 373.831 ms 373.879 ms 374.79 ms 7 121.ATM3-0.XR2.LAX4.ALTER.NET (146.188.248.110) 375.665 ms 374.306 ms 373.71 ms 8 193.at-1-1-0.TR1.LAX9.ALTER.NET (152.63.112.174) 373.284 ms 373.43 ms 372.938 ms 9 131.at-5-0-0.TR1.DFW9.ALTER.NET (152.63.3.161) 408.254 ms 429.138 ms 404.189 ms 10 289.at-1-0-0.XR1.DFW9.ALTER.NET (152.63.98.29) 404.381 ms 407.777 ms 410.8 ms 11 185.ATM6-0.BR3.DFW9.ALTER.NET (152.63.100.169) 406.129 ms 404.228 ms 404.08 ms 12 137.39.93.10 (137.39.93.10) 433.381 ms 415.909 ms 413.664 ms 13 pos10-0-0.lax-c100.gw.epoch.net (155.229.123.125) 416.909 ms 414 ms 416.23 ms 14 pos4-1.pao-c000.gw.epoch.net (155.229.120.49) 414.646 ms 416.578 ms 414.258 ms 15 pos8-0-0.npa-m100.gw.epoch.net (155.229.57.74) 417.329 ms 421.818 ms 600.575 ms 16 tig-us-pas-1.ihug.net (207.214.25.225) 420.169 ms 417.283 ms 417.213 ms 17 202-49-88-201.ihug.net (202.49.88.201) 531.449 ms 532.27 ms 530.245 ms 18 atm-5-0-0-2-netgate-akl.ihug.net (202.49.88.42) 531.121 ms 531.005 ms 530.884 ms 19 a0-0-0-2.tkbr1.netgate.net.nz (202.37.246.121) 534.236 ms 532.467 ms 530.545 ms 20 s1-1-1.labr1.netgate.net.nz (202.37.245.170) 767.038 ms 734.685 ms 768.571 ms 21 s5-0-0.lsanca1-cr1.bbnplanet.net (4.24.24.17) 681.512 ms 733.892 ms 751.962 ms 22 p2-1.lsanca1-ba1.bbnplanet.net (4.24.4.5) 765.545 ms 755.466 ms 680.472 ms 23 p7-0.lsanca1-br1.bbnplanet.net (4.24.4.2) 679.542 ms 766.558 ms 752.332 ms 24 p2-0.lsanca1-br2.bbnplanet.net (4.24.4.14) 750.405 ms 680.72 ms 765.398 ms 25 p1-0.crtntx1-ba1.bbnplanet.net (4.24.6.78) 808.366 ms 792.82 ms 806.672 ms 26 p1-0.crtntx1-ba2.bbnplanet.net (4.24.4.242) 786.897 ms 790.172 ms 770.245 ms 27 4.24.147.38 (4.24.147.38) 781.226 ms 782.357 ms 785.577 ms 28 pos10-0-0.lax-c100.gw.epoch.net (155.229.123.125) 850.728 ms 782.862 ms 782.42 ms 29 pos4-1.pao-c000.gw.epoch.net (155.229.120.49) 788.301 ms 782.932 ms 786.786 ms 30 pos8-0-0.npa-m100.gw.epoch.net (155.229.57.74) 840.266 ms 841.006 ms 785.38 ms 2000 isn't very long ago. It would be interesting to see what a similar unallocated route leaked into a significant provider would achieve today. David.