Re: [Idr] Input on AS Prepend for draft-idr-rpd-15.txt - Ends 02/24/22

[Job Snijders <[e-mail]>]

Hi all,

(no hats)

On Thu, Feb 10, 2022 at 09:53:44PM +0000, Keyur Patel wrote:
> IDR is requesting input on the use of AS prepend in BGP policy. This
> begins a 2 week call for requested input on the beneficial use of AS
> Prepend. draft-ietf-grow-as-path-prepending-05.txt indicates there is
> a risk in excessive prepending. In section 5, this draft suggests
> there is no need to prepend more than 5 ASN in an AS Pathway by a
> single AS.  Is this recommendation firm or likely to change?  Should a
> comment be added to the draft-ietf-rpd-15.txt security section to
> point to the draft-ietf-grow-as-path-prepending-05.txt draft?
> 
> The RPD draft can be found at:
> https://datatracker.ietf.org/doc/html/draft-ietf-idr-rpd. The AS Path
> Prepending draft can be found at:
> https://datatracker.ietf.org/doc/html/draft-ietf-grow-as-path-prepending.
> This call will end on Feb 24th 2022.

A challenge with the recommendation as currently outlined in
draft-ietf-grow-as-path-prepending-05 ultimately is that it is a
so-called "magic constant". Magic constants in an ever growing routing
system could potentially impede future growth.

At GROW @ IETF 110 in the Q&A of an update on the draft I (and I believe
others) suggested to try to come up with a formula or some kind of
function into which certain properties of the default-free zone's
current observable state produce a useful number; rather than a magic
constant, to make the draft's recommendation somewhat future-proof. If
I'm not mistaken, an alternative to the 'magic constant' has not yet
materialized.

I'd be hesitant to reference draft-ietf-grow-as-path-prepending from
draft-ietf-rpd at this point in time.

Kind regards,

Job