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

William Herrin bill at herrin.us
Wed Jul 21 20:39:15 EDT 2021

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

This is factually incorrect. It's uncommon but legitimate practice to
employ a private AS number which is dropped from the path by your
upstream provider.

> 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”

This wording is extremely vague. It's difficult for me to understand
how any router implementing something more complex than a default
gateway has not implemented a routing policy unique to its network.

"Multihomed" I understand. It just means you have two or more ISPs at
the same time.

> 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.

This is not entirely accurate. Any multi-organization internetwork
using the BGP protocol requires coordination of AS numbers no
different than they need coordination of IP addresses. It's not just
the public Internet.

> 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.

Can't we just be rid of justified needs analysis for AS numbers? What
exactly is the objective of preventing someone who thinks they want an
AS number from getting one? There aren't really any scarcity issues
and having or lacking an AS number doesn't particularly change one's
ability to introduce routes into the public BGP table.

William Herrin
bill at herrin.us

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