[arin-ppml] Draft Policy ARIN-2021-3: Private AS Number and Unique Routing Policy Clarifications

Scott Leibrand scottleibrand at gmail.com
Tue Jul 20 23:29:40 EDT 2021


On Tue, Jul 20, 2021 at 12:52 PM ARIN <info at arin.net> wrote:

> On 15 July 2021, the ARIN Advisory Council (AC) accepted "ARIN-prop-298:
> Private AS Number and Unique Routing Policy Clarifications" as a Draft
> Policy.
>
>
>
> <snip>
>
> Draft Policy ARIN-2021-3: Private AS Number and Unique Routing Policy
> Clarifications
>
>
>
> Problem Statement:
>
>
>
> At ARIN 47, staff identified three points of potential confusion with
> current text in NRPM Section 5: AS Numbers.
>
>
>
> 1. “Sites that do not require a unique AS Number should use one or more of
> the AS Numbers reserved for private use.” Some customers are not aware that
> their need for a unique AS Number depends upon their need (or lack thereof)
> to utilize the AS Number on the public Internet.
>
>
>
> 2. “In order to be assigned an AS Number, each requesting organization
> must provide ARIN with verification that it has one of the following…A
> unique routing policy (its policy differs from its border gateway peers)…A
> multihomed site.” Few customers qualify for an AS Number under the “unique
> routing policy” requirement, specifically because they aren’t aware of what
> “unique routing policy” applies to.
>
>
>
> 3. “AS Numbers are issued based on current need. An organization should
> request an AS Number only when it is already multihomed or will immediately
> become multihomed.” All ARIN delegations are based on current needs, and
> some customers aren’t aware they need network plans when they request an AS
> Number. Additionally, clarification that some organizations may have a
> unique need for an AS Number outside of utilizing a unique routing policy,
> such as BGP.
>
>
>
> Policy statement:
>
>
>
> In Section 5 -
>
>
>
> Replace
>
>
>
> “Sites that do not require a unique AS Number should use one or more of
> the AS Numbers reserved for private use.”
>
>
>
> with
>
>
>
> “Private ASNs should be used only when there is no plan to use them on the
> public Internet.”
>

I am not necessarily opposed to this change, but am not clear on what the
rationale is for it, and therefore on whether or not its effects match our
intent. The existing text requires that everyone who doesn't need a unique
ASN (for use on the public Internet) use a private ASN. The new text
recommends that private ASNs *only* be used by networks who aren't using
them on the public Internet. The new text does not require or even
recommend that sites running BGP internally use a private ASN, as the
original text did: it just recommends against the reverse.

One practical effect of this change would be that ARIN would be going on
record against multihomed organizations using a private ASN, peering with
an upstream, and having the upstream strip the private ASN from their
announcements so that they're originated from the upstream's ASN. Maybe
that would be a good change, now that 4-byte ASNs are widely usable and
there's no shortage. But if so, we need to revise the problem statement to
actually make that argument. Right now, it just states that "some customers
are not aware" of the meaning of the current policy, and then inverts the
policy without any further rationale for doing so.


>
> Replace
>
>
>
> “1. A unique routing policy (its policy differs from its border gateway
> peers) 2. A multihomed site.”
>
>
>
> with
>
>
>
> “1. A plan to connect their network using a unique routing policy, such as
> Border Gateway Protocol (BGP) 2. A network requiring routing policies to be
> deployed which are unique only to that network”
>

Another way to address the issue Chris raised here would be to just add the
word "with" before Border Gateway Protocol, so it reads "... using a unique
routing policy, such as with Border Gateway Protocol (BGP) ..."


>
> Replace
>
>
>
> “AS Numbers are issued based on current need. An organization should
> request an AS Number only when it is already multihomed or will immediately
> become multihomed.”
>
>
>
> with
>
>
>
> “AS Numbers should be requested when an organization has network plans
> ready and is either planning to use a unique routing policy (such as BGP)
> or has a unique need for an AS Number.”
>

Adding "with", so it reads "(such as with BGP)" would also be a good
clarification here.

-Scott
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