Best practices for BGP Communities

Wed Mar 6 14:52:46 UTC 2019

Thanks for all the feedback.

Follow up questions:

How does one distinguish "informational" and "action" of unknown
communities?

Also, why would a transit provider go out of their way to remove unknown
communities that don't have any meaning within their network? What benefit
would it serve the transit provider?

Best,
Josh

On Tue, Mar 5, 2019 at 8:18 PM Job Snijders <job at instituut.net> wrote:

> On Wed, Mar 6, 2019 at 8:32 Smith, Courtney <Courtney_Smith at comcast.com>
> wrote:
>
>> On 3/5/19, 6:04 PM, "NANOG on behalf of Job Snijders"
>> <nanog-bounces+courtney_smith=comcast.com at nanog.org on behalf of
>> job at instituut.net> wrote:
>>
>>     On Sun, Mar 03, 2019 at 08:42:02PM -0500, Joshua Miller wrote:
>>     > A while back I read somewhere that transit providers shouldn't
>> delete
>>     > communities unless the communities have a specific impact to their
>>     > network, but my google-fu is failing me and I can't find any
>> sources.
>>     >
>>     > Is this still the case? Does anyone have a source for the practice
>> of
>>     > leaving unknown communities alone or deleting them?
>>
>>     https://tools.ietf.org/html/rfc7454#section-11
>>
>>
>> Remember policies between two peers may not be same as customer policies.
>>
>> Example:  Customers_of_transit_X >>> Transit X >>> Peer_A >>
>> Customers_of_Peer_A
>>
>> Customers_of_Peer_A may use community A:50 to set local pref to 50 in
>> Peer_A network.  But that doesn’t not mean Customers_of_transit_X can send
>> A:50 to set lpref on their routes in Peer_A's network.  Peer_A's policy
>> with Transit X likely does not take action on customer communities since
>> they are 'peers' not customers.  Transit X can send A:50 to Peer_A but
>> nothing would happen.  What's the benefit of Transit X preserving A:50 from
>> its customers if it means nothing in Transit X?
>
>
>
> OP didn’t specify what kind of BGP communities they were referring to. In
> general we can separate communities into two categories: “Informational”
> and “Action”. You are right that preserving/propagating “action”
> communities (such as in your example) probably isn’t that interesting.
> “informational” communities on the other hand can be very valuable.
>
> See https://tools.ietf.org/html/rfc8195 for more information on how the
> two types differ.
>
> Kind regards,
>
> Job
>
>
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