Outbound Route Filtering (ORF) vendor support

Wed Aug 18 23:11:38 UTC 2021

ORFs are a challenging feature and haven't gotten a lot of deployment for a number of reasons.

At a high level, they're a very coarse filter.  Since each new ORF type adds to the logical AND condition, you start having to be more and more permissive in what you permit in the policy.  Since a significant amount of common ISP policies require matching things in tuples, this doesn't translate super well into many types of automatically generated ORFs.

The ext-community-orf feature was effectively supplanted by Rt-Constrain (RFC 4684).

The as-path ORF was challenging because different vendors have different ideas about what "regex" means and what the input tokens are.  Consider for example Juniper vs. Cisco regex matching.  The abstract fix would have been to define a regex that is for the feature.  I half suspect if people pushed on this these days, they'd want PCRE. :-)

The RD-ORF work is part of some ongoing discussion about how to deal with VRF overwhelm (prefix-limit exceed).

-- Jeff (IDR co-chair)

> On Aug 18, 2021, at 1:10 PM, Douglas Fischer <fischerdouglas at gmail.com> wrote:
> 
> Hello!
> 
> I also found a recent draft(expires Novembre 2021) about using Route Distinguisher as a Value on ORF.
> https://datatracker.ietf.org/doc/draft-wang-idr-rd-orf/ <https://datatracker.ietf.org/doc/draft-wang-idr-rd-orf/>
> 
> 
> 
> 
> Em qua., 18 de ago. de 2021 às 11:41, Humberto Galiza <humbertogaliza at gmail.com <mailto:humbertogaliza at gmail.com>> escreveu:
> Hi,
> 
> Is anyone aware of any vendor that supports Outbound Route Filtering
> (ORF) based on anything other than prefix-lists?
> 
> I found these two old IETF drafts (both expired :-/) which supported
> the idea of filtering based on community and as-path respectively, but
> I wasn't able to understand if they were ever discussed at the WG and
> if there was any outcome of the discussion (I suspect the authors are
> no longer even working with the mentioned companies in the drafts):
> 
> - https://datatracker.ietf.org/doc/html/draft-chen-bgp-ext-community-orf-02 <https://datatracker.ietf.org/doc/html/draft-chen-bgp-ext-community-orf-02>
> - https://datatracker.ietf.org/doc/html/draft-ietf-idr-aspath-orf-13 <https://datatracker.ietf.org/doc/html/draft-ietf-idr-aspath-orf-13>
> 
> Any info is very much appreciated.
> 
> Thanks,
> 
> 
> -- 
> Douglas Fernando Fischer
> Engº de Controle e Automação

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