Comcast Internet services had a major Domain Name Service (DNS) outage yesterday across the Eastern states which essentially broke Internet service for most Comcast customers.  This brought back some bad memories of a really bad week for Comcast in April of 2005 when Comcast suffered two DNS outages in the same week.

DNS can be thought of as the “phone book” of the Internet that allows your computer to translate www.google.com to something like 74.125.19.99.  The Internet’s routers don’t know how to route traffic going to www.google.com but they do know how to route traffic to 74.125.19.99.  If DNS is broken, your computer won’t be able to surf the web or retrieve email or do much of anything else on the Internet.

Some customers who were using 3rd party DNS service from Google DNS or OpenDNS were not affected, and I actually set up my home network to use the ISP, Google, and OpenDNS so that I have double redundancy.  DNS is a service that automatically fails over to a secondary and third DNS server if the first fails.  When two or three DNS services are set up in a home router, the router will automatically fail over and ensure that every computer in the home network will continue to function.  Home computers by default point to the home router for DNS and the router will by default relay to the ISP’s DNS service, but a user can add additional DNS servers for redundancy.

Of course the easiest thing to do for an ISP is to simply redirect customers to an alternative DNS resolver until the primary ones are repaired.  DNS resolvers are very easy to build and cheap to operate and it is strange why Comcast and some other ISPs have so much trouble with their DNS.  Even if they need to point their customers to Google DNS (which doesn’t sell customer IP address and web browsing habits to advertisers like OpenDNS), that would be a great strategy for customer satisfaction.  Most customers probably have no idea how to change their DNS settings to an alternative operational DNS server, so it’s crucial that ISPs keep DNS functioning one way or another.

There are a few ISPs like Sprint Wireless that redirect all DNS traffic to their own servers making it very difficult for customers to use alternative DNS services.  This is something that needs to be addressed at a best practices level on the Internet though ISPs should simply adopt practices that pleases their customers especially when it has no impact on their existing business models.

Tip – If you want set your DNS to Google DNS, just point your DNS to 8.8.8.8 and 8.8.4.4.  Those IP addresses are very easy to remember.  If you want to do it manually on your Windows computer, try this tutorial on DNS configuration.  Mac people can go here.  The router is the easiest place to change and it fixes every computer on your home network.  The procedure is different for each router, but it’s easy enough to find the manual or search the Internet for instructions on your router model.