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Traffic engineering and peering for CDNs

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

I hope this helps

Tom Smyth

On Mon, Jun 6, 2016 at 6:53 PM, Mike Hammett <nanog at ics-il.net> wrote:

> Some rely on performance testing to the client's DNS resolver and if
> they're not using on-net ones, they'll be directed to use a different CDN
> node.
> -----
> Mike Hammett
> Intelligent Computing Solutions
> http://www.ics-il.com
> Midwest Internet Exchange
> http://www.midwest-ix.com
> ----- Original Message -----
> From: "Graham Johnston" <johnstong at westmancom.com>
> To: "nanog at nanog.org" <nanog at nanog.org>
> Sent: Monday, June 6, 2016 8:36:43 AM
> Subject: Traffic engineering and peering for CDNs
> Lately I have been putting in some effort to maximize our IX connections
> by trying to work with the top 5-ish list of ASNs that still send us
> traffic via a paid transit connection despite the fact that we are both
> present on the same IX(s). In one case I missed the fact that one ASN
> wasn't using the IXs route-servers, that's on me for not spotting that one.
> Even with proper IX peering in place though it seems like some CDNs are
> better at using the IX connections than others. ASN 15169 for instance does
> an excellent job sending more than 99.99% of traffic via the IX connection;
> thank you. While others only seem to manage to send 60 - 80% of traffic via
> the IX. What I am not understanding about the respective CDN's network
> wherein they don't send traffic to me through a consistent path? Is the
> content coming from widely different places and rather than transport it
> across their own network from a remote site they would rather hot-potato it
> out a local transit connection? Are their transit costs so low that they
> don't care about using an IX connection over transit unlike a small
> operator like me? Is this just a non-obvious issue wherein they maybe just
> can't originate enough of the traffic near the IX and therefore don't make
> use of the IX connection, again a hot-potato phenomenon?
> Secondly can someone explain to me why some CDNs want a gigabit or two of
> traffic to be exchanged between our respective networks before they would
> peer with me via a public IX? I totally get those kinds of thresholds
> before engaging in a private interconnect but I don't understand the
> reluctance with regard to a public IX, that they are already established
> at. Is it again just a simple case of bandwidth economics that operate at a
> different scale than I can comprehend?
> I'm hoping the community can shed some light on this for me as I'm trying
> to avoid grilling the operators that are working with me as I don't expect
> those front line individuals to necessarily have a full view of the factors
> at play.
> Thanks,
> Graham Johnston
> Network Planner
> Westman Communications Group
> 204.717.2829
> johnstong at westmancom.com<mailto:johnstong at westmancom.com>
> P think green; don't print this email.

Kindest regards,
Tom Smyth

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