[Session variable] sync_client_id, sync_client_id_hash, and sync_originator_id [Usage] 
Used to identify the client that is currently synchronizing. An ID is typically used for conflict detection and to prevent echoing of changes back to the client during bidirectional synchronization. For more information, see How to: Exchange Bidirectional Incremental Data Changes Between a Client and Server. By default, Synchronization Services identifies each client with a GUID, which is returned by sync_client_id. You can also create a hash of the ID and use sync_client_id_hash in queries; or map the GUID to an integer and use sync_originator_id. For more information, see the "Examples" section later in this topic.