Return two locations or low TTL [was: DNS caches that support partitioning ?]

Patrick W. Gilmore patrick at
Mon Aug 20 18:29:38 UTC 2012

On Aug 20, 2012, at 10:07 , "Dobbins, Roland" <rdobbins at> wrote:
> On Aug 20, 2012, at 5:56 PM, Patrick W. Gilmore wrote:
>> My question above is asking Mark how you guarantee the user/application selects the A record closest to them and only use the other A record when the closer one is unavailable.
> I understand - my point was that folks using a GSLB-type solution would generally include availability probing in the GSLB stack, so that a given instance won't be included in answers if it's locally unavailable

How does that allow for a long TTL?  If you set a 3600 second TTL when the DC is up, and the DC goes down 2 seconds later, what do you do?

> (obviously, the GSLB can't know about all path elements between the querying resolver and the desired server/service).

Says who? :)


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