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@greendragon.com> To: <nanog@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!"