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How CDNs and Alternative DNS Services Combine For Higher Latency
The_PHP_Jedi writes "Alternative DNS services, such as OpenDNS and Google Public DNS, are used to bypass the sluggishness often associated with local ISP DNS servers. However, as more websites, particularly smaller ones, use content distribution networks via embedded ads, widgets, and other assets, the effectiveness of non-ISP DNS servers may be undermined. Why? Because CDNs rely on the location of a user's DNS server to determine the closest server with the hosted content. Sajal Kayan published a series of test results which demonstrates the difference, and also provided the Python script used so you can test which is the most effective DNS service for your own Internet connection."
"Pair" in question is a pair of nipples, apparently.
I think you're missing the point. Geographically aware DNS is used to send you to your nearest deployment of an application. Deciding after you've arrived is too late.
Automatically routes your DNS request to a Google server close to you. So there's no problem here.
Slashdot.org is serving static assets from the hostname a.fsdn.com which is served via Akamai CDN. I count 19 requests to http://a.fsdn.com/* on a single pageload of the homepage. These static files are currently served by a server within my ISPs network rather than some server on the other side of the globe... Alamai uses DNS routing.
It isn't just ads. For example, Microsoft, Apple, Symantec, and Red Hat use CDNs for distributing software updates (that's just a few companies I know of off the top of my head). Basically, CDNs keep the Internet working, saving server load at the source and bandwidth across the Internet and at the providers.
CDN:s (Content Delivery Networks for those who don't know. I can't believe these things have to be spelled out on /. Quality really has gone downhill) are not only used for advertising. They are used to serve all kinds of resource-intensive content. Such as porn. And streaming video. Let's say you're an Aussie with your website hosted on the Australian mainland. Then you'll pay premium for international bandwidth because Australia has crappy connections to the rest of the world. So you want international visitors to get their images and other static content you don't change regularily from a CDN to reduce your bandwidth costs.
Football Odds
Why wouldn't I use OpenDNS? They may be working for profit but it is free to individuals. Also, I disagree that they are the "exact same ads" when they consist of a few text links and I trust them more than Comcast. But more importantly, assuming you were correct that they are the same ads, the other benefits far outweigh this nit. The ability to whitelist/blacklist domains and block them by category is more than worth the price of admission, which again is free. Then throw in useage reports... To ignore all that because of the "exact same ads" is shortsighted. The company I work for started using this and the incidents of crapware have gone way down. I've set it up on all my family's computers and recommend it to others.
The whole point of a CDN (the middle initial) is distribution, theoretically to a broad area.
For example, without a CDN, you have 3 servers, all located in San Francisco. The guy who lives in Florida (or Russia, or South America) who requests content from your server will receive it much more slowly than the guy who lives in Vegas.
With a CDN, there will be servers all over the nation (and preferably around the world, if you serve internationally) which will be physically closer to the requestor that can serve with a lower latency. The servers within the CDN farm utilize reverse DNS lookup to balance and serve traffic from the correct place.
Grammar Lesson: you're is a contraction of "you are"; your means you possess something; yore means days gone by.
I'm the founder of OpenDNS (and long-time slashdot reader).
This article is not very accurate for a number of reasons. First, both my service (OpenDNS) and Google's are co-located in similar POPs to all of the major CDNs which causes this problem to be largely avoided. The author of the blog post used a tiny sample size and tested mainly from EC2 instances, neither of which helps his cause.
1) EC2 instances are BY DESIGN not co-located in the same place as major peering infrastructure because that real estate costs more. They are one or two hops away. People use EC2 for compute power, not for routing performance. So he needs to use something like Keynote or Gomez to test from home connections. If he had, he'd see it doesn't impact anything, and often improves performance, especially in the US. We don't have POPs in Asia yet, though they are coming this year, and when we do, we'll improve things for him.
2) Akamai is the only CDN where this will ever be perceptible because their deployments are so dense. They have 3000+ pops which means they will also be able to target more precisely. But this is being worked on RIGHT NOW in the IETF -- http://tools.ietf.org/html/draft-vandergaast-edns-client-ip-01
Anyways, this is really not the issue the author makes it out to be, and for the edge cases, they are being worked on.
Thanks,
David
# Hack the planet, it's important.
...so those in the know can select the nameserver(s) closest to them without having to depend upon a 3rd party to determine (sometimes erroneously) what servers are closest.
Ok so by "shoddy CDN companies" you mean every CDN anyone here has ever heard of? And the vast majority of enterprises that have hot/hot (public) datacenters?
Using anycast for serving content is a guarantee of fail. Great for DNS, less than ideal for HTTP. How serious a failure depends on important reliable and consistent end user experience is. Using geolocation based on the actual source address for content within the pages is a very intelligent thing to do in addition to doing it at the LDNS level initially.
On the innertubes anycast is good for things for which UDP is appropriate (even if they use other transports), and it can be acceptable for HA between a hot and a warm datacenter, but it's just not robust enough for a "CDN".
This still violates the DNS specification, and there is no way to effectively turn it off. Why is this a problem? Please see: http://en.wikipedia.org/wiki/DNS_hijacking#Use_by_ISPs .
For this reason I use Internet2, Level 3's (4.2.2.2 - 4.2.2.4), and now google's dns servers.
I fear the Y2038 bug
Most wiretapping laws that I am aware of do not protect you from 'eaves dropping' from private companies when you're using their services.
Change is certain; progress is not obligatory.