2.2.3.1.1.2.5.31 TTL
The TTL element specifies the time, in hours, during which the settings remain valid. It is an optional child element of the Protocol element (section 2.2.3.1.1.2.5).
A value of "0" (zero) indicates that rediscovery is not required. If the TTL element is omitted, the default value is "1".
