On Wed, Jul 13, 2011 at 11:02 PM, Michael Hallgren <[email protected]> wrote: > Le mercredi 13 juillet 2011 à 18:25 +0200, Daniel Verlouw a écrit : >> see >> <https://puck.nether.net/pipermail/juniper-nsp/2010-July/017473.html> >> >> Not supported. I requested an ER back then, don't think it ever got >> implemented... > > Thanks Daniel, I'll do the same then... Must be considered pretty basic > from a regexp point of view, I think. Right? :)
>From a user and standardization perspective, they seem pretty simple, but are actually difficult to implement very efficiently since the time it takes to do the search is non-deterministic. Here's a nice accessible write-up about DFA vs NFA regex engines that touches on this: http://swtch.com/~rsc/regexp/regexp1.html Honestly, what's the use case of a backreference for an AS path? It seems like BGP loop detection would never allow a path like "A X X A", in which case if it's just used to search for repetition (as mentioned above), why not just use the "+" and "*" operators? e.g. "^(701 )+" Cheers, jof _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
