188.8.131.52.5 Handling Asynchronous Responses
If SMB2_FLAGS_ASYNC_COMMAND is set in the Flags field of the SMB2 header of the response and the Status field in the SMB2 header is STATUS_PENDING, the client MUST mark the request in Connection.OutstandingRequests as being handled asynchronously by storing the AsyncId of the response in Request.AsyncId. The client SHOULD<149> extend the Request Expiration Timer, as specified in section 184.108.40.206. Processing of this response is now complete.
If SMB2_FLAGS_ASYNC_COMMAND is set in the Flags field of the SMB2 header and Status is not STATUS_PENDING, this is a final response to a request which was processed by the server asynchronously, and processing MUST continue as specified below.