ttl for ns

Fri Aug 13 14:45:44 UTC 2004

1.    It's a financial issue. In the event of an emergency or an server 
failure, how many hours can you financially be offline. Are your customers 
willing to wait up to 2 days for their DNS caches to update with the new IP 
address?

A very busy domain might benefit from having a higher TTL value for their 
nameserver's but having a lower TTL for hosts, so that you minimize your 
downtime, in the event of a server failure. For example, when Akamai was 
having DNS issues, content providers with low TTL's were able to switch to 
secondary nameservers faster, than zones with using a higher TTL.

2.    It's a performance issue. Zones with a lower TTL have slightly higher 
server usage. If you set a low TTL value will your nameservers be able to 
handle that increased load?

Personally, I use a TTL of 4 hours. It's low enough so that in the event of 
a failure, I can easily migrate my hosts, but still high enough that there 
isn't a significant server load.

-- Matthew

----- Original Message ----- 
From: "William Allen Simpson" <wsimpson at greendragon.com>
To: <nanog at merit.edu>
Sent: Thursday, August 12, 2004 11:20 PM
Subject: ttl for ns

> Having no guidance so far from this group, despite the grumbling about
> times becoming shorter and lack of analysis, I thought "Well, vixie
> will know the best practice!"