Traffic engineering and peering for CDNs

Wed Jun 8 15:40:44 UTC 2016

On 6/7/16, 2:46 AM, "NANOG on behalf of Mark Tinka"
<nanog-bounces at nanog.org on behalf of mark.tinka at 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.