On Aug 20, 2012, at 06:49 , "Dobbins, Roland" <[email protected]> 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
