Habitually Good

A post at Digital Inspirations (a blog I frequently read) inspired me to finally get down and measure the performance of OpenDNS as an alternative to your ISPs DNS Server. I live in India and since there are no OpenDNS servers in India, logically, despite the massive hardware behind the OpenDNS offering, the local ISP’s DNS Server should be better performing (because any advantage that OpenDNS might have in query resolving would be offset by the response time for the DNS query).

Now, let’s see if this is true. I used the excellent tool by Charles Putney available on Code Project for testing the DNS response times: DNSTester. The tool tests the DNS response times for a given pair of DNS Servers against a random selection of domain names. I ran this tool a number of times and captured the response time data for 100 different domains.

Below, I present the results and following that, some observations and conclusions:

As you can see, this is a plot of time taken to resolve the DNS query for 100 different domains by my ISP (Airtel) and OpenDNS. Here’s another graph that summarizes the same data:

Now, this chart clearly shows that on average my ISP is faster at resolving DNS queries (as expected logically).

There are some observations that I made:

Consistency: Looking at the graph above, you can see that OpenDNS was more or less consistent in resolving the queries, while my ISP was all over the place. Some queries were resolved very fast while others took forever.

Popularity of Domain - I noticed while collecting this data that the sites for which my ISP was orders of magnitude faster than OpenDNS were usually the more popular sites (such as youtube, yahoo, msn, aol, etc.). While on not so popular sites, my ISP was either comparable or slower. For really obscure sites, OpenDNS was orders of magnitude faster.

Conclusions:

• If you mostly visit popular sites when you surf, you are much better off using your ISP’s DNS server (this is of course true in India or other places where there is no local OpenDNS presence).
• In my case, I visit at least 20 sites a day which I have never visited before. So for users like me, OpenDNS might just bring more benefit overall.

Of course, OpenDNS offers other benefits that your ISP doesn’t, so that might also work as a tradeoff for pure speed.

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