[db-wg] "AND NOT" in as-expression
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Job Snijders
job at instituut.net
Tue May 27 14:59:24 CEST 2014
Dear Aris, On Wed, May 21, 2014 at 04:59:11PM +0200, Aris Lambrianidis wrote: > On 14 May 2014, at 14:20 , Job Snijders <job at instituut.net> wrote: > > My follow up question, which actually is indirectly related, is if > anyone is willing to share an opinion, as to whether "OR" can/should > be used implicitly in as-expressions, besides filter expressions. > > This currently seems to not be the case (the RIPE test database > doesn't accept it) and I wonder whether I am interpreting the RFC > incorrectly or if it's something that can be considered valid and > thus, honored. What Aris proposes is the following, instead of writing this: import: from AS-ANY except ( AS1 OR AS2 OR AS3 ) accept ANY One can compress as following: import: from AS-ANY except ( AS1 AS2 AS3 ) accept ANY In other words: when AS or AS-SETS are grouped together, an implicit OR is inserted between the individual AS expressions. This is slightly different compared to what one is allowed to do inside filter-expressions. However, I oppose this proposal for the following reasons: - this is NOT specified in any RFC (most specifically rfc2622) - allowing this type of syntax is merely syntactic sugar - this change is NOT backwards compatible with existing RPSL parsers - a simple workaround exists: use AS-SETS * better readability * easier to maintain in an automated fashion Therefor, I recommend the following policy structure if one wants to exclude a set of ASNs from a specific import or export statement: as-set: AS-EXCLUDED-ASNS members: AS1 members: AS2 members: AS3 aut-num: xxx import: from AS-ANY except AS-EXCLUDED-ASNS accept ANY Kind regards, Job
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