SOA record (DNS)

From ben.goodacre.name/tech

SOA record metrics:

Refresh: This is the number of seconds between update requests from secondary and slave name servers. If notifies are enabled this is a fairly redundant feature.

Retry: This is the number of seconds the secondary or slave will wait before retrying when the last attempt has failed.

Expire: This is the number of seconds a master or slave will wait before considering the data stale if it cannot reach the primary name server.

Minimum: Previously used to determine the minimum TTL, this is used for negative caching. This is the default TTL if the domain does not specify a TTL.

TTL (time to live) - The 'standard' TTL, this is the number of seconds any DNS record is cached on a DNS server that queries your NS before expiration and return to your (authoritative) nameservers for updated information. Reducing TTLs is commonly done when moving sites between physical environments.

http://support.microsoft.com/kb/163971