188.8.131.52 RID Master FSMO Role
The RID Master FSMO role owner is the single DC responsible for processing RID Pool requests from all DCs within a given domain. It is also responsible for moving an object from one domain to another during an interdomain object move.
When a DC creates a security principal object such as a user or group, it attaches a unique SID to the object. This SID consists of a domain SID (the same for all SIDs created in a domain) and a relative ID (RID) that is unique for each security principal SID created in a domain.
Each DC in a domain is allocated a pool of RIDs that it is allowed to assign to the security principals it creates. When a DC's allocated RID pool falls below a threshold, that DC issues a request for additional RIDs to the domain's RID Master FSMO role owner (see [MS-DRSR] section 184.108.40.206.3, PerformExtendedOpRequestMsg with ulExtendedOp = EXOP_FSMO_RID_REQ_ROLE). The RID Master FSMO role owner responds to the request by retrieving RIDs from the domain's unallocated RID pool and assigns them to the pool of the requesting DC (see [MS-DRSR] section 220.127.116.11.12, ProcessFsmoRoleRequest with ulExtendedOp = EXOP_FSMO_RID_REQ_ROLE). There is one RID Master FSMO role per domain in a directory.
See section 18.104.22.168 for more information about the RID Master's role in interdomain object move operations.