7. Apr. 2009

The Time to live (TTL)s occuring  in the Domain Name System (DNS), where they are set by an authoritative nameserver for a particular resource record can help us speeding up domain transfers rfom one server to another.

When a caching (recursive) nameserver queries the authoritative nameserver for a resource record, it will cache that record for the time (in seconds) specified by the TTL. If a stub resolver queries the caching nameserver for the same record before the TTL has expired, the caching server will simply reply with the already cached resource record rather than retrieve it from the authoritative nameserver again.

This is a service intended to speed up DNS queries and to prevent load issues on authoritative nameservers. Therefore shorter TTLs can cause heavier loads on an authoritative nameserver, but can be useful when changing the address of critical services like web servers or MX records, and therefore are often lowered by the DNS administrator prior to a service being moved, in order to minimize disruptions.

And this is exactly what we can use to speed up the transfer time of our domain to move. At least a day before the big bang to happens we enter our Hosting Panel trilling down to the DNS section within and lower the TTL for each relevant definition within the definitions of the domain in question.

The units used are seconds. A common TTL value for DNS is 86400 seconds, which is 24 hours. A TTL value of 86400 would mean that if a DNS record was changed, DNS servers around the world could still be showing the old value from their cache for up to 24 hours after the change.

Lowering it should be done with some respect about the idea behind and therefore the new value does not really should be close to 1 or so, but going with 600 for a day will for sure not harm.

When we now change the nameserver entry within our Registrar’s Service, all old values will get invalidated within 10 minutes and the new authoritative nameserver will get asked instead.

So all the traffic should then get routed over to the new server in a blink and the higher value there for the TTL will propagate again through the World Wide Web.

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