AS-Path - ORF Draft

Job Snijders job at
Mon Oct 23 05:36:24 CST 2017

On Sun, Oct 22, 2017 at 05:37:52PM -0500, Mike Hammett wrote:
> Network A was sending more routes into the route server than Network B
> could handle. Network B would like Network A's routes filtered before
> they even got to their router. 
> Googling a bit I saw pages talking about saving CPU or what have you,
> but the main thing was Network B has a limited FIB. They have a prefix
> limit specified to protect that. Their device goes through prefix
> limit before prefix filter, so their filters wouldn't even see the
> advertisements as the prefix limit already killed the session. Raise
> the prefix limit so that the filters can get to work and now you're
> vulnerable to someone else injecting a ton of routes and melting their
> router. 
> If that draft were supported by Network B's router and the route
> servers, I believe that Network B could tell the route servers to
> filter Network A's prefixes before sending them, thus saving their
> FIB. 

Your interpretation of the functionality described in the draft is
correct. Work on this draft started in december 2000 as can be read
here: I am not
aware of any implementations, and having read the draft and observing
there are no IANA codepoint assignments yet, it is very unlikely there
are any implementations available for production use.

Generally speaking it is safe to say that 17 year old Internet-Drafts
(without known implementations) may be lacking the required traction to
become a RFC.

So alternatively, network B can tell the route server operator via email
"do not send me these prefixes", and the route server operator in the
middle honors that request and doesn't send those prefixes to network B.
Some IXP's offer a webportal for this type of functionality, other IXPs
allow signaling via RPSL in the IRR or as mentioned before, email.

> Obviously the most correct answer is for Network A to get routers with
> big enough FIBs, but that's not always possible or practical. 

s/Network A/Network B/ - Yes, this can be a challenge. I fear that
bgp-aspath-orf won't be of any help in the short term.

Kind regards,


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