In my comments, it’s more about avoiding de facto “standards” in favor of having actual “standards” or following existing actual “standards”. There are RFCs that cover what the OP wants. There is an IANA well-known Communities registry that can be expanded to record any additional functionality OP wants from communities without creating de facto standards. The problem with so-called “de facto standards” is that there’s an open question of who decides what the standard is and how much credibility they have and/or can maintain over time. There’s also the problem that nothing prevents someone who doesn’t like someone else’s “de facto standard” from creating one of their own. In some cases, everyone yawns and ignores the new standard. In other cases, the old standard fades in favor of the new. In most cases, the community fractures, both standards gain some traction and neither standard wins creating more chaos than standard in the end.

IMHO, that’s a real document-able reason.

YMMV.

Owen


On Sep 8, 2020, at 1:06 PM, Mike Hammett via NANOG <nanog@nanog.org> wrote:

Is there more desire to be flexible because people are snowflakes and their idea is the only way it should be or real, document-able reasons?



-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

Midwest-IX
http://www.midwest-ix.com

From: "Tom Beecher" <beecher@beecher.cc>
To: "Mike Hammett" <nanog@ics-il.net>
Cc: "NANOG" <nanog@nanog.org>, "Douglas Fischer" <fischerdouglas@gmail.com>
Sent: Tuesday, September 8, 2020 3:02:37 PM
Subject: Re: BGP Community - AS0 is de-facto "no-export-to" marker - Any ASN reserved to "export-only-to"?'

I also get that intent from the OP. However I disagree that there should be a 'de facto' standard created for such things. All flavors of BGP community specifications are designed to be flexible so that different networks can design a system that is tailored to their needs. 

Having 'de facto' standards does not simplify in my opinion. I believe it just creates more work for operators trying to navigate around different opinions of what 'de facto' means. 




On Tue, Sep 8, 2020 at 2:35 PM Mike Hammett <nanog@ics-il.net> wrote:
How I see the OP's intent is to create a BCP of what defined communities have what effect instead of everyone just making up whatever they draw out of a hat, simplifying this process for everyone.



-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

Midwest-IX
http://www.midwest-ix.com

From: "Tom Beecher via NANOG" <nanog@nanog.org>
To: "Douglas Fischer" <fischerdouglas@gmail.com>
Cc: "NANOG" <nanog@nanog.org>
Sent: Tuesday, September 8, 2020 1:30:19 PM
Subject: Re: BGP Community - AS0 is de-facto "no-export-to" marker - Any ASN reserved to "export-only-to"?'

BGP Large Communities ( https://tools.ietf.org/html/rfc8195 ) already provides for anyone to define the exact handling you wish. 



On Tue, Sep 8, 2020 at 11:57 AM Douglas Fischer via NANOG <nanog@nanog.org> wrote:
Most of us have already used some BGP community policy to no-export some routes to some where.

On the majority of IXPs, and most of the Transit Providers, the very common community tell to route-servers and routers "Please do no-export these routes to that ASN" is:

 -> 0:<TargetASN>

So we could say that this is a de-facto standard.


But the Policy equivalent to "Please, export these routes only to that ASN" is very varied on all the IXPs or Transit Providers.


With that said, now comes some questions:

1 - Beyond being a de-facto standard, there is any RFC, Public Policy, or something like that, that would define 0:<TargetASN> as "no-export-to" standard?

2 - What about reserving some 16-bits ASN to use <ExpOnlyTo>:<TargetASN> as "export-only-to" standard?
2.1 - Is important to be 16 bits, because with (RT) extended communities, any ASN on the planet could be the target of that policy.
2.2 - Would be interesting some mnemonic number like 1000 / 10000 or so.

-- 
Douglas Fernando Fischer
Engº de Controle e Automação