When a system load is requested, a response is returned immediately and the load proceeds in the background. If an error is detected this trap is generated indicating the reason why in the status, as follows:- (1) file not found; (2) access violation; (4) illegal TFTP operation; (5) unknown transfer ID; (7) no such user; (8) no response from the load server; (9) the download could not be started because of a lack of resources; (10) the length of a record differs from that implied by the value of the record length field; (11) the record type is not recognised; (12) record checksum error; (13) the device type in the file is incorrect; (14) the software image is not suitable for this version of the hardware; (15) the first record in the file was not a file header; (16) The byte count reported in the file trailer record differed from the number of bytes actually received. When loading a new image into the device containing the agent itself, the agent first reads the beginning of the image file to test if it is accessible and contains a valid image. If there is anything wrong, this trap is generated, no download is performed and the device continues to run uninterrupted. If this check is successful the download proper is begun. Should that fail, it is simply retried continuously until either an attempt succeeds or the device is reset.