On 6/7/16, 2:46 AM, "NANOG on behalf of Mark Tinka" <nanog-boun...@nanog.org on behalf of mark.ti...@seacom.mu> wrote:
> > >On 6/Jun/16 20:03, Tom Smyth wrote: > >> as far as im aware ... a friend of mine on INEX in Ireland said most >>cdns >> use source ip of the DNS requests to determine which network to direct >>them >> to ... so if you use you have your own resolver on an ip address in >>your >> network range cdns can accurately determine what network the request is >> comming from and determine what ip address / what network that the cdn >>has >> nearest to your network... >> >> ff you use 3rd party dns servers for your clients... you may not get an >> optimal ip answer for your dns queries from the CDNS involved > >Some CDN's use DNS (in addition to latency, congestion levels, busy >state, e.t.c.). > >Others use Anycast routing, which I tend to prefer. The problem is the >latter run a network while the former may typically not. > >Mark. Also some companies make layer 7 decisions for their CDN¹s in conjunction with these other methods. Their applications makes a decision on what host to send you to based on routing information, your source address, and other accumulated data.