What percentage of nameservers honor TTL these days?

Solution 1:

We moved recently and had all sorts of problems with DNS.

When we did the swing over most customers started hitting the new IPs right away. But some were still hitting the old IPs for weeks. We left a server up for a month or so. Eventually we went through the IIS logs on the old machine and called the customers telling them to flush DNS on there company or ISP DNS servers. That got the last of them moved over.

It was a small number of people that kept with the old IPs. Out of 20k customers, maybe 50 had issues after the first day.

Solution 2:

(Very) long TTL values of weeks are in May 2011 honoured by most DNS resolving nameservers up to 2 weeks.

In a test using just-dnslookup.com, having 50 global distributed active measuring point, with an A record TTL set to 99.999.999 = 165 weeks (precise: 165 weeks 2 days 9 hours 46 minutes 39 seconds), and a default TTL of 2 weeks (= SOA + NS TTL).

First lookup returns:

• a TTL of 1 week, for 3 out of 50 measuring points
• a TTL of 165 weeks, for 47 out of 50 measuring points

Consecutive lookups return (converted in to original TTL value):

• a TTL of 1 week, for 3 out of 50 measuring points
• a TTL of 2 weeks, for 46 out of 50 measuring points
• a TTL of 165 weeks, for 1 out of 50 measuring points

A second test (using a different domain) where default TTL is set to 4 weeks (= SOA + NS TTL) results are below.

First lookup returns:

• a TTL of 1 week, for 3 out of 50 measuring points
• a TTL of 2 weeks, for 1 out of 50 measuring points
• a TTL of 165 weeks, for 46 out of 50 measuring points

Consecutive lookups return (converted to full TTL length):

• a TTL of 1 week, for 3 out of 50 measuring points
• a TTL of 2 weeks, for 47 out of 50 measuring points
• a TTL of 165 weeks, for 0 out of 50 measuring points

From the most well known/best connected public resolver services:

• Google public DNS [8.8.8.8 and 8.8.4.4] reduce to 1 day.
• UltraDNS [rdns(1|2).ultradns.net] honour full 165 weeks.
• Sprintlink [ns(1|2|3).sprintlink.net] honour full 165 weeks.

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Solution 3:

I recently moved DNS for a few domains that host my personal site and project sites from GoDaddy to in-house DNS (yeah, literally my house). Overall, every site that I have remote access to respected the TTL and made the transition well. The same was reported by every friend I could ask to check, both via landline and mobile. The only problem, ironically, were the main caching DNS servers at $University where I work, which seemed to totally disregard TTL for cached queries (and even disregard the TTL value they were assigning to the cached result).

Seems like, overall, TTL should be well-respected. 56% of servers authoritative for .com and .net domains are running BIND, which obviously plays well with the standards. Cablevision/Optimum (at least in NJ) seems to be using Nominum CNS, which also respects TTLs.