Zerigo

More features

• Global network
• REST API
• Simple management
• Instant updates
• Domain import tools
• Master/slave support
• Flexible billing
• All features

Instant updates, low TTLs

There are two key measurements when measure the speed of DNS updates. One is the time it takes for an update to make it to the authoritative DNS server. The second, the TTL, is the maximum period of time until everyone across the internet sees the update.

[Website or API] -> (update time) -> [DNS servers] -> (TTL) -> [internet users]

Instant updates

When you make a change to your DNS records, it takes a moment for them to replicate to all of the DNS servers. Until this happens, nobody can see the change.

Zerigo's proprietary synchronization engine ensures this happens in mere seconds. We won't name names (to protect the guilty), but many providers take hours to perform updates. In our opinion, that's crazy and it's why we designed our system for much faster updates.

Low TTLs

Once a change hits the DNS servers, then the TTL (time-to-live or refresh time) comes in to play. The TTL is the maximum amount of time an intermediate DNS server, such as an ISP's DNS server, is allowed to cache a DNS response before verifying it with the official server again.

This caching mechanism is very useful as it allows remote DNS servers to deliver a repeat response back to end users much more quickly. However, it does mean that changes made to the official DNS server may not be seen by your users for some time.

Imagine a TTL of 24 hours. User A goes to your site at 8pm. At 9pm you make a change to your DNS. Until 8pm the next day, user A will continue to use the old (and now stale) DNS information. Not good.

Zerigo allows TTLs as short as 1 minute. This does increase the volume of DNS queries that must be answered, so just a couple of minutes isn't necessarily a good idea for everyone. If 15 minutes works for you, great. If 12 hours makes more sense, that's fine too. The key is it should be your choice.

Often the best answer is to set it a bit longer (between 1 hour and 1 day) and drop it to 5 minutes a day or two before an anticipated change. Once the change has been made, go back to the original value.

If your DNS provider sets minimum TTLs of an hour or two (and there are many), your users are stuck waiting.

Be sure to consider the need to make quick changes (expected or unexpected) to DNS records when evaluating DNS providers.