BGP Path Attribute Filtering, YES or NO?

James Jun james.jun at towardex.com
Wed Jan 8 14:52:38 UTC 2020


On Wed, Jan 08, 2020 at 04:36:29PM +0200, Mark Tinka wrote:
> 
> We provide customers with a ton of LOCAL_PREF options they can activate
> in our network via communities:
> 
>  http://as37100.net/?bgp
> 
> As I mentioned to Saku re: the ORIGIN attribute, I don't mind customers
> using this on us since we have sufficient backbone capacity in all
> markets, and they pay us to provide them with a port in each market. So
> if customers want to change our LOCAL_PREF values in order to push
> traffic some way or another, we are okay with this, since it's $$.
> 

I see.  LOCAL_PREF and RFC 1998 style of community attributes however are
 not the right tool for signalling exit locations -- it does not scale.
Sure, it's a useful hammer to hard enforce a baseline mode of preference
on given route (e.g. route of last resort, backup or equalize to same
baseline level as peer-learned routes, etc), but for signalling optimal
exit locations at scale, MED is exactly the right tool for that job (and
networks would typically derive MED values using IGP metrics).

I'm not concerned about ORIGIN attr, as that's abuse of interconnection, so
slightly a different situation.  But, denying the ability for customers 
who have ports at multiple locations to use MED isn't very ideal. 

James



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