Among the responses to the original posting was this comment. Does it make sense?
===== Keith Brady 5:21pm on Monday, December 20th, 2010 # Reply The “somehow uses our DNS routing to determine our location” is actually quite straightforward. All major internet services (Akamai and Google included) look up the IP address of the querying DNS server (usually your ISP’s server) in a location database (something like doing ‘whois w.x.y.z’ to look up RIPE et al) to figure out your approximate location and serve the IP address of a nearby point of presence (e.g. Datacenter or peering point). The tricky bit there is that they use the IP address of the DNS server, not the original requester. Usually that’s nearly the same thing since it’s your ISP (or your own one) and you are routing out to the internet in much the same way. The problem comes when you’re using OpenDNS or GoogleDNS. While they both have many servers that are globally distributed (using anycast to do that despite using a single IP address) these servers aren’t as close to you as your ISP’s and will have a funneling effect. There’s a modification to the standard in progress for the requesting DNS server to pass along the IP address of the querying client and that will make a lot of this go away. AFAIK, GoogleDNS does this and Google servers can take advantage of it (though it’s a proposed standard and so open). ===== On Fri, Dec 31, 2010 at 1:27 PM, Mike Veltman <[email protected]> wrote: > > Thats a bit odd, because its based on the clients ip, not the dns ip. > > Otherwise I would also have problems with Microsoft downloads because they are > also akamai based. > > So this can not be the whole explanation.. > > On 31 December 2010 12:57:57 Soh Kam Yung wrote: >> [ >> http://apple.slashdot.org/story/10/12/31/0110226/Beware-of-Using-Google-Or >> -Open-DNS-For-iTunes ] >> [ http://joemaller.com/2577/itunes-slowdowns-with-google-dns/ ] >> >> Anybody else using Google or Open DNS and encountered a similar issue >> with location based servers? >> >> ===== >> Beware of Using Google Or Open DNS For iTunes on Thursday December 30, >> @11:20PM Posted by timothy on Thursday December 30, @11:20PM >> from the speak-friend-and-enter-slowly dept. >> >> Relayman writes "Joe Mailer wanted to download an iTunes movie >> recently and his Apple TV told him it would take two hours. When he >> switched his DNS resolver settings, the download time dropped to less >> than 20 seconds. Apparently, iTunes content is served by Akamai which >> uses geolocation based on the IP address of the DNS request to >> determine which server should provide his content. When you use Google >> or Open DNS to resolve the Apple domain name, all the requests to >> Akamai appear to be coming from the same location and they're all >> directed to the same server pool, overloading that pool and causing >> the slow downloads. The solution: Be wary of using Google or Open DNS >> when downloading iTunes files or similar large files. Use your own >> ISPs DNS servers instead or run your own resolving DNS server." >> ===== > > -- > With regards, > Mike Veltman > -- Soh Kam Yung my Google Reader Shared links: (http://www.google.com/reader/shared/16851815156817689753) my Google Reader Shared SFAS links: (http://www.google.com/reader/shared/user/16851815156817689753/label/sfas) _______________________________________________ LUGS Mailing list - [email protected] List FAQ: http://wiki.lugs.org.sg/LugsMailingListFaq Info page: http://www.lugs.org.sg/mailman/listinfo/slugnet To unsubscribe send an empty email to: [email protected]
