HE.net BGP origin attribute rewriting

Thu May 31 12:33:27 UTC 2012

On May 31, 2012, at 8:03 AM, sthaug at nethelp.no wrote:

>> I disagree.  Origin is tremendously useful as a multi-AS weighting
>> tool, and isn't the blunt hammer that AS_PATH is.
> 
> If you think of AS_PATH as a blunt hammer, how would you describe
> localpref?
> 
> We use AS_PATH in many cases *precisely* because we don't consider it
> to be a blunt hammer...
> 

So you're connected to providers A and B, who in turn connect to C.  Additionally, B has customer D.

If you set origin E toward B (leaving origin I toward A) you influence C's decision without affecting either B or D, and you ensure that C still learns both routes to you.  It's a more subtle nudge than as-path.

In general, I prefer routinely using attributes that are further down the algorithm so at the big guns can be saved for when they're needed or for special policy issues.

David Barak

Sent from a mobile device, please forgive autocorrection.