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From: Leigh Porter <leigh.porter@ukbroadband.com> To: Leo Bicknell <bicknell@ufp.org> Date: Tue, 8 Nov 2011 22:15:03 +0000 In-Reply-To: <20111108213600.GA70357@ussenterprise.ufp.org> Cc: "nanog@nanog.org" <nanog@nanog.org> Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org On 8 Nov 2011, at 21:37, "Leo Bicknell" <bicknell@ufp.org> wrote: > In a message written on Tue, Nov 08, 2011 at 04:22:48PM -0500, Christoph= er Morrow wrote: >> I think actually it wouldn't have caused more validation requests, the >> routers have (in some form of the plan) a cache from their local >> cache, they use this for origin validation... there's not a >> requirement to refresh up the entire chain. (I think). >=20 > I kinda think everyone is wrong here, but Chris is closer to accurate. > :P >=20 > When a router goes boom, the rest of the routers recalculate around > it. Generally speaking all of the routers will have already had a > route with the same origin, and thus have hopefully cached a lookup > of the origin. However, that lookup might have been done > days/weeks/months ago, in a stable network. >=20 > While I'm not familar with the nitty gritty details here, caches > expire for various reasons. The mere act of the route changing > paths, if it moved to a device with a stale cache, would trigger a > new lookup, right? >=20 > Basically I would expect any routing change to generate a set of > new lookups proportial to the cache expiration rules. Which may very well fail because all the routing is hosed. I'm not all tha= t familiar with the potential implementation issues, but I would think tha= t network-local caches would be in order.=20 Even with local caches, I would expect a high incidence of change to trigg= er something sensible to mitigate this kind of craziness from happening. I= am sure enough people have had incorrectly scaled RADIUS farms blow up wh= en a load of DSLAMS vanish and come back again not to repeat such storms. -- Leigh Porter ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email=20 ______________________________________________________________________
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