Mods to ripe181?

Oh, so we have another major providers needs such function.

						--Jessica
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To: Jessica Yu <jyy at merit.edu>
cc: rr-impl at ripe.net, enke at mci.net
Subject: Re: Mods to ripe181? 
In-reply-to: Your message of "Fri, 03 Feb 1995 15:02:30 EST."
             <199502032002.PAA23182 at home.merit.edu> 
Date: Fri, 03 Feb 1995 16:15:52 -0500
From: Enke Chen <enke at mci.net>

I agree with Jessica on the need of AS path in the as policy. 
The reality is that AS paths are widely used today in AS policies 
today.  Here is a very simple example, currently MCInet does 
not re-distribute to other NSPs the routes learned from a NSP.
This policy is very difficult (if not impossible) to describe 
without AS path. 

- -- Enke    


> Date:    Fri, 03 Feb 1995 15:02:30 -0500
> From:    Jessica Yu <jyy at merit.edu>
> To:      rr-impl at ripe.net
> CC:      jyy at merit.edu

> This issue may come up before but never got addressed.  Now we have real probl
em
> 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 explicitl
y
> 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, w
e 
> 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

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