Directory Services

Configuration of TTL Limits

A client can request a TTL value for an entry ranging between 1 and 31557600 (i.e., 1 second to 1 year). This attribute value range will be enforced by the Range-Lower and Range-Upper attribute values in the attributeSchema definition for the entryTTL attribute. As per RFC 2589, directory servers are not required to accept this value and might return a different TTL value to the client. Clients must be able to use this server-dictated value as their client refresh period (CRP) which will govern how often the client will need to perform the refresh operation on the dynamic entry.

Active Directory will provide administrators with the ability to configure the default and minimum TTL values for a forest. The default TTL value is what will be assigned to a newly created dynamic entry if a TTL is not explicitly specified. The minimum TTL will override any client specified TTL value that is lower than the configured minimum. No configurable maximum TTL value needs to be provided since a maximum will be imposed by the Range-Upper attribute value in the attributeSchema object. Allowing administrators to configure these values will enable them to set TTL values which will enforce a low refresh traffic or, at the other extreme, provide a highly up-to-date directory.

The default values for the two configurable TTL parameters will be as follows:

The configurable TTL parameters will be stored as AVA (attribute value assertion) entries of the form "<value-name>=<value>" in the attribute ms-DS-Other-Settings of the NTDS-Service object given by the following DN in the Configuration partition:

CN=Directory Service,CN=Windows NT,CN=Services,CN=Configuration,DC=…

The exact AVA syntax for the two configurable TTL parameters is as follows where NNNN is expressed in seconds:



These values can be set by an administrator through the command-line utility ntdsutil.