3.2.1.1 Cache of GPO Versions
A table of the following information is present on the client, indexed by GPO GUID, as part of the efficient implementation of the protocol:
GPO Container Version: GPO version that is stored in the Active Directory portion of the GPO.
GPO File System Version: GPO version that is stored in the SYSVOL file system portion of the GPO.
The client maintains this information (even across system restarts) after every Group Policy application protocol conversation so that clients do not overwhelm the Group Policy server. As part of any future policy application protocol sequence, these cached attributes can be compared against those attributes that are being retrieved for each GPO returned by the server. If both version numbers are identical, this can be interpreted as meaning that there are no changes to administrative intent since the last policy application; thus, there is nothing new for the client to enforce because it is assumed to be in compliance from the earlier policy application.
Thus, as an optimization, the client can choose not to include some of the Group Policy extension sequences for some extensions to Group Policy to avoid unnecessary network usage and client or server processing.