Shane, Many moons ago ANS used the advisory attribute for transit across their network and they required all their route objects to have such a field. Other than that use I never heard of anyone using it for anything other purpose. To my knowledge, ANS was the reason for the advisory attribute. When we converted to RPSL we dropped support for the advisory attribute and it was filtered out of all route objects.

As for how the attribute is actually used, I found 2726 route objects with the attribute. Of these, there are only 111 unique origin AS. As for the AS actually listed as the target of the advisory, there are only 13 unique AS! The actual frequencies are:

This suprises me since to my knowledge we no longer supported this attribute. So I grep'd our production DB cache for 'advisory' and it did not show up. So where are you finding all these occurences? --jerry

Shane, On Fri, Nov 03, 2000 at 02:47:42PM +0100, Shane Kerr wrote:

I've been looking over the 'advisory' attribute, mostly in preparation for the upcoming RIPE-181 to RPSL conversion (RPSL does not have this attribute).

The advisory attribute itself suffers from a severe lack of documentation. In the current database documents, we see the following:

RIPE-157: listed as for the route object, with the format <ASnnnn> <as-specific information>

RIPE-181: not present

RIPE-189: in the route template only

You can find the following if you do a search for 'advisory attribute' on the RIPE NCC's own webpage: The documentation is here: ftp://ftp.ripe.net/ripe/docs/ripe-131.txt (note that I didn't invent this ugly attribute, I was the one who documented it ...) and in: http://www.ripe.net/ripe/wg/db/r25-db.html: Brian Renaud proposed to obsolete the advisory: attribute for aut-num: objects. For 'route:' objects, these atrtributes should remain valid. Ther was general agreement and the NCC was asked to implement that change. It doesn't look like we ever made a decision about also obsoleting it for the 'route:' class. But as has been said before on this, they are not really relevant anymore and should be removed (note that this has nothing to do with RPSL, RPSL only defines the attributes that are relevant for RPSL itself and doesn't say that you can't have an 'advisory' attribute any longer).

So, some questions are: Is there a BCP for this attribute? And can anyone explain how and why it is used? Can somebody suggest an alternative method to obtain the same results in RPSL? And finally, what should the method be during RIPE-181 to RPSL conversion?

Delete it as is done in the ripe2rpsl conversion script that was written by me and Cengiz: ... # # delete as-exclude/advisory attributes delete($entry{"ae"}); delete($entry{"av"}); ... David K. ---