Well I think the answer is - it depends. First IXP fabric can be used as pure L3 share LAN or can be used (and it is often the case) as a p2p emulated VLAN over such L3 shared LAN.
Now if this is L3 shared LAN still customer and ISP may peer directly and no third party traffic would be accepted at either end. If we talk about emulating L2 IXP fabric becomes just an emulated circuit and from the perspective of routing it a p2p interface. Sure the other aspects of the IXP quality, port monitoring, oversubscription etc... always will apply but there are ways to mitigate or handle those in real IXPs. Best, R. On Tue, Mar 8, 2022 at 9:05 PM Christopher Morrow < christopher.mor...@gmail.com> wrote: > > > On Tue, Mar 8, 2022 at 2:36 PM Sriram, Kotikalapudi (Fed) > <kotikalapudi.sriram=40nist....@dmarc.ietf.org> wrote: > >> This question has relevance to the ASPA method for route leak detection. >> >> Is it possible that an ISP AS A peers with a customer AS C via a >> non-transparent IXP AS B? >> IOW, the AS path in routes propagated by the ISP A for customer C's >> prefixes looks like this: A B C. >> I.e., can the AS of a non-transparent IXP/RS appear in an AS path in the >> middle between an ISP and its customer? >> >> > it seems unlikely to me that an ISP would pick up a 'customer' (someone > that pays them to transport packets) at an IXP fabric. > Might it happen? sure? is it messy? yes! > > 1) that's probably a shared port > 2) there are other folk feeding routes and packets into the mix > 3) how many came through the 'customer' port (which you can't really know > easily) vs other participants on the ix > 4) what capacity planning could the 'customer' do here? (none, basically > with respect to the remote ISP port) > > Your question might work also as: > "ISP A has a customer C on a direct link in location Y. > ISP A is present at IXP-Z, so is customer C, though they do not > bilaterally peer (not do they interconnect at the IXP). > ISP A can still see Customer C's routes through the IXP-Z Route Server." > > that seems plausible, but not a desired outcome for the ISP :) since they > will be unlikely to collect pesos for the traffic > which MAY pass across that interconnect. > > _______________________________________________ > GROW mailing list > GROW@ietf.org > https://www.ietf.org/mailman/listinfo/grow >
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