Use of advisory attribute

[Shane Kerr <]

Routing Folks,

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

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:

   AS517: 8 
   AS670: 1
   AS690: 2703
   AS702: 2
  AS1275: 13
  AS1717: 1
  AS1755: 2
  AS2917: 5
  AS3220: 3
  AS3257: 1
  AS3328: 1      
  AS3561: 1
  AS6830: 2

AS690, the Merit network, seems to have a specific format for their
advisory attribute (which I can guess at, but not really be sure what it
means).  This is not shared by all of the other AS's who use the
advisory attribute.

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?

-- 
Shane Kerr shane@localhost
Database Software Engineer
RIPE NCC
+31 20 535 4427