Chunk server: rework remote sync state machine list to eliminate list search at the state machine shutdown / removal, and always remove state machines from the list on shutdown. Implement chunk server and chunk access forwarding with chunk close rpc. Implement chunk server authentication with remote sync state machine by obtaining chunk server access from the write lease on the write master, or from the replication chain on the write slave, decrypting, if needed, session key, and finding and / or creating a new remote sync state machine with the delegation token, and the corresponding session key. Store, obtain and pass down the replication chain chunk server and chunk access tokens. Implement chunk server and chunk access in chunk replication state machine.