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

Robert Raszuk <robert@raszuk.net> Wed, 28 March 2012 20:30 UTC

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Date: Wed, 28 Mar 2012 22:30:21 +0200
From: Robert Raszuk <robert@raszuk.net>
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To: Brian Dickson <brian.peter.dickson@gmail.com>
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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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Brian,

The customer's workaround was to erase entire AS_PATH via 
redistribution. I am not saying that use of this knob is safe.

I am saying that it exists in shipping implementations and simply asking 
what SIDR behaviour should be when such policy is present.

That's all.

Best,
R.

> 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
> <mailto: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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