[ncc-services-wg] Locally caching riswhois results

--On 21 July 2008 13:28:38 +0200 Laurent Zimmerli 
<laurentz at student.ethz.ch> wrote:
> I'm making use of the riswhois service and would like to cache queries
> locally. However, I am not sure whether I can do it the way I want to. My
> idea is to store the ASN an the corresponding route of each query I
> execute. Before performing another query I would then check whether I
> already stored the ASN of a route which contains the IP for which I want
> to find the AS.
> Can I do that? Or is then the following case possible: I store an AS an
> its route -- say  ASx, 123.0.0.0/8 -- whose IP range includes another one
> -- say ASy, 123.100.0.0/16. When I store ASx first and then query an IP
> of ASy, I will assign ASx to this IP instead of ASy. Is such a case
> possible? Or is there even another problem with my caching approach?

Yes, overlapping prefixes originating from different autonomous systems do 
exist in the wild.

The problem I see is that when you find a matching prefix in your cache 
from one particular AS  you would return that (or what's the point of the 
cache) and won't know whether there is a more specific (longer) prefix 
originating from a different AS which a query to riswhois would return.

I can't really see a way around this problem except to use a local copy of 
the RIS RIB dumps in the same way that riswhois does.

James