[Dnsmasq-discuss] DNSMasq and CDN (akamai, etc)
simon at thekelleys.org.uk
Fri Jul 8 11:28:06 BST 2011
I don't know if this
is going anywhere (the latest draft has expired) but if it does then
support in dnsmasq may be in order.
Ed W wrote:
> I have a curious problem being served sub-optimal CDN servers when using
> opendns or googledns
> I am in London/UK and opendns appears not to have a local DNS cache, so
> attempting to access bbc.co.uk and view the page images gives these results:
> # dig news.bbcimg.co.uk
> ; <<>> DiG 9.7.3 <<>> news.bbcimg.co.uk
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57231
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0
> ;; QUESTION SECTION:
> ;news.bbcimg.co.uk. IN A
> ;; ANSWER SECTION:
> news.bbcimg.co.uk. 2413 IN CNAME newsimg.bbc.net.uk.
> newsimg.bbc.net.uk. 202 IN CNAME news.bbc.co.uk.edgesuite.net.
> news.bbc.co.uk.edgesuite.net. 3427 IN CNAME a1733.g.akamai.net.
> a1733.g.akamai.net. 10 IN A 22.214.171.124
> a1733.g.akamai.net. 10 IN A 126.96.36.199
> ;; Query time: 84 msec
> ;; SERVER: 192.168.105.212#53(192.168.105.212)
> ;; WHEN: Fri Jul 8 10:22:02 2011
> ;; MSG SIZE rcvd: 168
> That ip range is in the USA and about 85ms away from me.
> Instead using google dns I get:
> # dig news.bbcimg.co.uk @188.8.131.52
> a1733.g.akamai.net. 19 IN A 184.108.40.206
> a1733.g.akamai.net. 19 IN A 220.127.116.11
> These are 41ms away
> If I switch to my ISP DNS servers:
> # dig news.bbcimg.co.uk @18.104.22.168
> a1733.g.akamai.net. 15 IN A 22.214.171.124
> a1733.g.akamai.net. 15 IN A 126.96.36.199
> These are 15ms away
> So having discovered that using nominally faster DNS servers has amongst
> other things the disadvantage that CDNs might pass you to suboptimal
> choices, hurting you multiple times per web page...
> So I tried this configuration:
> But I notice that since the reply comes back in a single response that
> the CNAMES are not resolved using the alternative server parts.
Yes, that approach is not tenable.
> Disregarding all the privacy debates about using these super DNS
> servers, does anyone have any thoughts on how to better handle getting
> redirected to a local CDN, other than perhaps using only the ISP servers?
I wonder if your ISP has a cache for the BBC content withing its
network? Traffci from bbc.co.uk must make up a huge proportion of
external traffic for UK ISPs.
Maybe try it the other way around, (ie use openDNS or Google DNS for
everything _except_ (list of big site likely to use local CDNs)
> Ed W
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
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