Re: [sidr] [Idr] AS_SET depreciation (RFC6472) and BGP multipath

Brian Dickson <brian.peter.dickson@gmail.com> Wed, 28 March 2012 20:25 UTC

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Date: Wed, 28 Mar 2012 16:25:06 -0400
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From: Brian Dickson <brian.peter.dickson@gmail.com>
To: robert@raszuk.net
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Cc: "idr@ietf.org List" <idr@ietf.org>, Paul Jakma <paul@jakma.org>, sidr wg list <sidr@ietf.org>
Subject: Re: [sidr] [Idr] AS_SET depreciation (RFC6472) and BGP multipath
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Arbitrary AS substitution allows loop creation, even if your own AS is
required.

All that is needed, is multiple instances of replace-as in the loop.

Suppose A replaces B C D with A E F.

Suppose B replaces G A with B C D.

A received B C D, sends A E F to G.

G sends G A E F to B.
B sends B C D E F to A.

We have a loop, which eventually results in path overflow with E F E F E F
etc. at the end of it.

On Wed, Mar 28, 2012 at 4:07 PM, Robert Raszuk <robert@raszuk.net> wrote:

>
>  the 'replace-as' seems like
>> loop-creation, joy.
>>
>
> Nope. No loops at least in one implementation ... the implementation
> mandates that you insert your own AS - that is not optional.
>
> Rgs,
> R.
>
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