Blog Fiasco

December 5, 2010

Comcast DNS problems

Filed under: The Internet — Tags: , , , , — bcotton @ 9:53 pm

As of this evening, it looks like Comcast is having problems with a few of their DNS servers.  The servers in Chicago and Detroit are offline, rendering the Internet nigh-unusable for many of their customers in parts of the midwest.  I haven’t seen any official announcement, other than the red lights on the DNS status page, but I’ve heard a lot of complaints from people using their mobile phones to connect to the Internet.  If you’re one of the affected customers, you can change your DNS settings to use any combination of the following servers:

  • OpenDNS: 208.67.222.222 and 208.67.220.220
  • Google: 8.8.8.8 and 8.8.4.4
  • Level3: 4.2.2.1 and 4.2.2.2

It’s interesting to me how different this is than it would have been a few years ago.  With the popularity of smart phones, many people have access that doesn’t rely on their ISP.  I’ve already provided support to several people on Twitter who are once again able to waste a Sunday evening surfing the web.  I wonder how much of a credit I’ll get on my bill.

Update, 10:29 PM: Engadget has a brief article up now.  Comcast has been providing updates via Twitter, but there’s currently no ETA for repair.

Update, 6:48 AM: Based on Twitter timestamps, it looks like Comcast engineers got things fixed around 2AM EST.  All of their servers are reporting OK.  I haven’t seen any explanation of what happened, but that will probably come later today.

December 7, 2009

Google DNS: A rare miss?

Filed under: The Internet — Tags: , , , , , — bcotton @ 9:20 am

I’ve been a big fan of Google’s services for many years. GMail, Google Calendar, Google Talk, Google Voice, and Google Docs are all a regular part of my day.  (Admittedly, I haven’t quite figured out how I’ll use Google Wave, but I’m sure there’s a use for it somewhere.) So when I heard about Google offering a DNS service, I was very interested.  DNS (the Domain Name Service) is a vital part of the Internet.  It is what allows people to visit Funnel Fiasco without having to remember that the IP address is 72.52.153.36. Or to visit www.facebook.com without typing in 69.63.181.11.

A while ago, I switched from using my ISP’s DNS service to OpenDNS.  OpenDNS gives users the option to filter domains by content, which is a somewhat useful tool for parents and businesses.  Unfortunately, OpenDNS, like most ISP DNS services, returns a search page when a domain isn’t found. Sure, that might be handy for web browsing, but other services expect to be told a domain doesn’t exist when it doesn’t exist.  Google said that they’ll return appropriate responses for non-existent domains.

Before I made the switch, I decided to investigate which DNS service gave me the fastest responses.  I tested 8 DNS servers from 4 different services (Google, Comcast, OpenDNS, and Level3) at different times over the past few days.  The final result surprised me.  Google’s service was slower than both Level3 and OpenDNS, and slower than one of the two Comcast servers I tested.  Box plots are below, although it seems some of the calculation is off (for example, a DNS resolve time < 0 ms is not reasonable).

DNS resolve times for google.com

DNS resolve times for google.com

DNS resolve times for funnelfiasco.com

DNS resolve times for funnelfiasco.com

DNS resolve times for facebook.com

DNS resolve times for facebook.com

Average hostname resolve times in milliseconds

Google #1
(8.8.8.8)
Google #2
(8.8.4.4)
Level3 #1
(4.2.2.1)
Level3 #2
(4.2.2.2)
OpenDNS #1
(208.67.222.222)
OpenDNS #2
(208.67.222.220)
Comcast #1
(68.87.72.130)
Comcast #2
(68.87.77.130)
Google.com 51 42 25 25 25 26 24 62
Funnelfiasco.com 41 40 46 26 37 26 41 87
Facebook.com 39 37 26 25 25 29 25 63

So what’s the conclusion?  Well, it looks like the Level3 servers (4.2.2.1 and 4.2.2.2) are the fastest.  Tests by intMain.net support my own conclusions. Google’s DNS service might be faster for some people, but not for everyone.  If Google adds more servers, that might change.  In the meantime, it looks like I have some resolv.conf edits to make.

(P.S. Box plots created thanks to software from Vertex42.com)

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