There may be a knob that AS operators have for permitting transitivity, but we need to look at measurements to understand whether or not operators actually allow transitivity to EC and LC.
NIST BGP measurements (thanks to my colleague Lilia Hannachi) were shared on the GROW list in May 2020: https://mailarchive.ietf.org/arch/msg/grow/JPD1-hhSvVXIZbUlNQ_1hmzD6IA/ A portion is copied below. The AS path length (# unique ASes) distributions for BGP updates with Communities (Regular, Large, and Extended) are shown here. It is evident that both LC and EC propagate multiple AS hops. Mass stripping of LC or EC at the first hop is not evident. The peak happens at AS path length 4 or 5 and that is good. That is the behavior that is helpful for route leak solution. The solution can still function even if some ASes strip. We can do some more detailed studies if needed. ********************************************************************* RIPE-RIS: Community ANALYSIS (Collector : rrc03 From 2020-04-30 00:00 To 2020-04-30 00:55) ********************************************************************* # Updates = 1075583 (Total) # (Regular) COMMUNITY = 859239 (79.89%) AS path length distribution = 1: 170 (0.02%) 2: 44803 (5.21%) 3: 141072 (16.42%) 4: 276271 (32.15%) 5: 238325 (27.74%) 6: 114158 (13.29%) 7: 31365 (3.65%) 8: 9018 (1.05%) 9: 2690 (0.31%) 10: 811 (0.09%) 11: 358 (0.04%) 12: 169 (0.02%) 13: 22 (0%) 14: 7 (0%) # LARGE_COMMUNITY = 152818 (14.21%) AS path length distribution = 2: 5655 (3.7%) 3: 17205 (11.26%) 4: 54372 (35.58%) 5: 45492 (29.77%) 6: 22065 (14.44%) 7: 6422 (4.2%) 8: 1068 (0.7%) 9: 397 (0.26%) 10: 71 (0.05%) 11: 35 (0.02%) 12: 26 (0.02%) 13: 6 (0%) 14: 4 (0%) # EXTENDED COMMUNITIES = 44606 (4.15%) AS path length distribution = 2: 2269 (5.09%) 3: 7435 (16.67%) 4: 17657 (39.58%) 5: 11600 (26.01%) 6: 3967 (8.89%) 7: 1221 (2.74%) 8: 371 (0.83%) 9: 57 (0.13%) 10: 19 (0.04%) 11: 8 (0.02%) 12: 1 (0%) 13: 1 (0%) ********************************************************************* Sriram _______________________________________________ GROW mailing list GROW@ietf.org https://www.ietf.org/mailman/listinfo/grow
