The AS-path at AS4 is (4 3 1). If you assume that AS1 and AS3 are bilateral peers, then both sides of AS3 declare AS3 not to be its provider. AS3 has both sides non-customer. That's a leak.
Regards, Jakob. > On Mar 21, 2022, at 10:31 PM, Zhuangshunwan <[email protected]> wrote: > > Hi Sriram and all, > > IMO, for the scenario described in the following email (AS4 and AS3 are P2P > connection; AS3 and AS1 are connected via a RS and being treated as a P2P > connection ), it can be determined that AS-PATH: AS4 AS3 AS1 is a route leak > if one of the following conditions is met: > 1. If AS1 is a Tier 1 ISP; > 2. AS3 is not included in the set of C2P AS numbers set registered by AS1; > 3. Determine that AS1 and AS3 are P2P relationships (one of the ways is to > obtain them is: a) Create a P2P relationships database; b) lookup in the P2P > relationships database); > 4. AS4 detects that AS3 and AS1 are interconnected through IXP (for example, > Traceroute), which is equivalent to a specific way of obtaining the P2P > relationship between AS1 and AS3 in branch 3. > 5. Make sure that AS3 is not the Customer of AS1 (it may be P2P, that is, > branch 3;(or) it may be P2C). > > Thanks, > Shunwan > >> -----Original Message----- >> From: Sriram, Kotikalapudi (Fed) [mailto:[email protected]] >> Sent: Tuesday, March 22, 2022 5:09 AM >> To: Jakob Heitz (jheitz) <[email protected]>; Jeffrey Haas <[email protected]> >> Cc: [email protected]; [email protected]; Zhuangshunwan >> <[email protected]>; Nick Hilliard <[email protected]> >> Subject: RE: [GROW] [Sidrops] ASPA and Route Server (was RE: IXP Route >> Server question) >> >> Hi Jakob, >> >>> To be clear, I'm talking about BGP devices that do not insert their ASN into >> the AS path. >> >> Even if you assume that all route servers are transparent, what would you >> like to propose to solve the following problem? >> >> AS1 (RS Client) -----> AS2 (RS) -----> AS3 (RS Client) ---p2p (lateral >> peer) ---> >> AS4 (validating AS) >> >> The arrows indicate the direction of the flow of the Update. Let us say that >> the RS is transparent. >> >> AS4 is the receiving/validating AS. The AS path is {AS3 AS1}. Do you agree >> this is a route leak as seen at AS4? The question is how will AS4 detect it? >> What ASPAs should be in place? >> >> Suppose the RS-clients (i.e., AS1 and AS3) have ASPAs each attesting the RS's >> AS (i.e., AS2) as a provider. That is all that it takes for AS4 to be able >> to detect >> the leak. >> >> Is there another way? Do we assume that AS1 and AS3 have some other ISP >> provider(s) for which they have ASPA attestation? >> >> In this solution, AS4 does not have to know anything about the presence of >> an RS, etc. >> >> This solution works fine even if the RS happens to be non-transparent. >> >> In an earlier related thread, >> >> https://mailarchive.ietf.org/arch/browse/sidrops/?gbt=1&index=I2a05YrOEY >> rRRdEg1ZHOOln6BCw >> >> Nick Hillard and Rob Mosher left the door slightly open for a possibility >> that >> there might be a rare RS out there that is non-transparent. >> >> Sriram _______________________________________________ GROW mailing list [email protected] https://www.ietf.org/mailman/listinfo/grow
