Default client cache time to live. Provides a default expiration interval in case a particular catalog record does not contain a valid catalog::Expiration value.
Real number, 0 or greater. Number of hours until expiration since the reply data was generated. Set to 0 to always expire the reply image immediately, which effectively disables client caching. Set to -1 to mark as
default::Expiration if not defined or if empty.
TTL (Time-To-Live) is the duration before the cache expires. The default TTL is 10 hours.