Re: [Sidrops] ASPA false leak

"Jakob Heitz (jheitz)" <jheitz@cisco.com> Wed, 16 October 2019 03:32 UTC

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From: "Jakob Heitz (jheitz)" <jheitz@cisco.com>
To: Randy Bush <randy@psg.com>
CC: SIDR Operations WG <sidrops@ietf.org>
Thread-Topic: [Sidrops] ASPA false leak
Thread-Index: AdWDr4IJUqd9dgFSRaS/zGHcilvp8QAE+p8AAAOVAtA=
Date: Wed, 16 Oct 2019 03:31:57 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/sidrops/OpGl1eqEs4B3UlZCrgKTxDZK5y0>
Subject: Re: [Sidrops] ASPA false leak
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The actual path is (5 4 3 2 1). Technically a leak.
However, all transited ASes are authorized, therefore it should be allowed.
The alternative is (5 4 1). Not a leak.

Regards,
Jakob.

-----Original Message-----
From: Sidrops <sidrops-bounces@ietf.org> On Behalf Of Randy Bush
Sent: Tuesday, October 15, 2019 6:46 PM
To: Jakob Heitz (jheitz) <jheitz@cisco.com>
Cc: SIDR Operations WG <sidrops@ietf.org>
Subject: Re: [Sidrops] ASPA false leak

> Consider the topology:
> 
>    AS5      AS3
>      \     /   \
>       \   /     \
>        AS4     AS2
>          \     /
>           \   /
>            AS1
> 
> AS1 has providers AS2 and AS4.
> AS2 has provider  AS3.
> AS4 has providers AS3 and AS5.
> 
> AS5 receives a route with AS-path (4 3 2 1).
> ASPA would declare that AS4 leaked the route from AS3 to AS5.
> However, AS4 is an authorized provider for AS1.
> Even though AS4 has a path to AS1, it chose to use an alternative
> valid path to reach AS1.

and that alternate path sure looks a lot like a route leak.

randy

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