Destination Preference Attribute for BGP

Fri Aug 18 21:13:37 UTC 2023

On 8/18/23 09:38, Robert Raszuk wrote:
> Jakob,
>
> With AS-PATH prepend you have no control on the choice of which ASN 
> should do what action on your advertisements.

My comprehension of DPA would have been more directed than the "spray & 
pray" approach AS_PATH prepending provides.

> However, the practice of publishing communities by (some) ASNs along 
> with their remote actions could be treated as an alternative to the 
> DPA attribute. It could result in remote PREPEND action too.
>
> If only those communities would not be deleted by some transit 
> networks ....

Even then, communities have best efficacy at the closest interconnect 
with the network that is using them. Since community values are 
generally not coordinated Internet-wide, it would take a laborious 
effort to construct the right set of communities to achieve the desired 
outcome for an end-to-end source or destination path, assuming those 
communities were not mangled in flight.

Mark.