Re: [Sidrops] [GROW] IXP Route Server question

Hi Sriram,

> The ASPA verification draft treats the relationship of RS to RS-client as similar
> to that of Provider to Customer. Seems reasonable? The AS of an RS client
> includes the RS's AS in its ASPA as a "Provider".
>

IMO, the ASPA verification draft regards the relationship between RS and RS-client as "peer-to-peer", maybe my understanding is wrong, I will read the ASPA verification draft again.

BR,
Shunwan

> -----Original Message-----
> From: GROW [mailto:grow-bounces@ietf.org] On Behalf Of Sriram,
> Kotikalapudi (Fed)
> Sent: Thursday, March 10, 2022 11:31 AM
> To: Nick Hilliard <nick@foobar.org>
> Cc: grow@ietf.org; sidrops@ietf.org
> Subject: Re: [GROW] IXP Route Server question
> 
> Nick and all,
> 
> Thank you. What you all shared/discussed is very useful info.
> 
> >Almost all RS's are transparent these days.  Usually IXPs go to lengths to
> ensure that the RS ASN doesn't appear in the AS path.
> 
> Good to know that. Well, that means there can be an occasional RS that is
> non-transparent. When there is a non-transparent RS, could there be big ISPs
> (Tier-1, Tier-2) present there as RS-clients?
> 
> The ASPA verification draft treats the relationship of RS to RS-client as similar
> to that of Provider to Customer. Seems reasonable? The AS of an RS client
> includes the RS's AS in its ASPA as a "Provider".
> 
> Sriram
> 
> -----Original Message-----
> From: Nick Hilliard <nick@foobar.org>
> Sent: Tuesday, March 8, 2022 4:28 PM
> To: Sriram, Kotikalapudi (Fed) <kotikalapudi.sriram@nist.gov>
> Cc: grow@ietf.org; sidrops@ietf.org
> Subject: Re: [GROW] IXP Route Server question
> 
> Sriram, Kotikalapudi (Fed) wrote on 08/03/2022 19:36:
> > 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?
> 
> Almost all RS's are transparent these days.  Usually IXPs go to lengths to
> ensure that the RS ASN doesn't appear in the AS path.
> 
> Some organisations provide transit over IXPs, but it's a minority thing.
> It would be very peculiar if an organisation provided transit over an IXP via
> an RS.
> 
> Some organisations provide transit to ASNs over a direct physical connection
> while maintain peering with their customer over an IXP port.
> Usually this happens by accident, but occasionally it can happen by design.
> 
> The answer to your question is that it would be technically possible, but it
> would be so peculiar and stupid that it should be considered a mistake in the
> situations where it was intentional. In all other situations, it would be a leak.
> Generally it would be safe to assume that this sort of configuration was in
> error.
> 
> Nick
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