On Aug 20, 2012, at 06:49 , "Dobbins, Roland" <rdobbins@arbor.net> wrote:
On Aug 20, 2012, at 5:24 PM, Patrick W. Gilmore wrote:
But I do not think returning multiple A records for multiple datacenters is as useful as lowering the TTL.
Some folks do this via various GSLB mechanisms which selectively respond with different records based on the assumed relative topological distance between the querying resolver and various server/service instantiations in different locations.
"Some folks" == "more than half of all traffic on broadband modems" these days. However, I think you missed a post or two in this thread. The original point was you need a low TTL to respond with a single A record or multiple A records which all point to the same datacenter in case that node / DC goes down. Mark replied saying you can respond with multiple A records pointing at multiple DCs, thereby allowing a much longer TTL. 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. -- TTFN, patrick