Mods to ripe181?

This issue may come up before but never got addressed.  Now we have real problem
to describe three major providers policies who I gather routing policies from.

I think we really need to seriously address this.  Below is an example to
illustrate the problem and a suggestion to the solution.  


                           ASh
                           |
                     ASi...ASj-------|
                      \  | /         |
                        130          |
                         |          /
                 ----------------- /
                  |       |    |  /
                 50      60    70 
                / \      / \    \
              ASm...ASn ASx..ASy ASz
               |
              ASa

The Policy:

AS130 announce to AS50 everything but not any routes whose AS path starts with
AS50,AS60 and AS70.

The difficulties here are 

a) AS130 wants to announce ASj to AS50 but not with
the pass of 100 ASj.  Since RIPE181 only has homeAS concept in terms of what
AS to accept, we have to either describe to reject ASj or advertise ASj not
advertise ASj when path is 130 ASj.

b) Usually, certain in this real AS's policy case, one does not know explicitly
what's behind AS130 i.e. ASi..Asj, ASh.  So it is near to impossible to 
express such policy in ripe181 format.

The problem is that RIPE181 deals with home AS only.  To describe this case, we 
need introduce a concept of AS in the path.

Suggested mods:

Introduce AS in the path concept.  This will solve both problem a) and b).  To 
express the policy above:

as-out: to AS50 announce ANY AND NOT {AS50in_the_path, AS60in_the_path AS70in_the_path}

I suggest to use cisco's regular expression to represent the AS in the path
concept.  It is widely used and therefore more people understands it.

as-out: to AS50 announce ANY AND NOT {^AS50_ ^AS60_ ^AS70_}

^ means the right most of the ASpath.
_ same as .* 


							--Jessica



-------- Logged at  Fri Feb 3 22:16:28 MET 1995  ---------