A file transfer protocol and implementation

This paper presents a file transfer service in a heterogeneous computer network (HMINET). The basic architecture models are presented, the file transfer protocol is described and the implementation in the HMINET is shown with the functional capabilities and the command structure. A transfer of files between different computer system can be regarded as a service, which is divided into four steps: A: access to a file, which is administrated in a File Management System (FMS), residing on one computer system B: transfer the file data by any transport medium C: creation of a file copy in another EMS D: additional operations on the transferred file, e.g. print out or conversion The usual case of file transfer (FT) between different computer systems is an offline transport by means of any storage medium (disks, tapes, etc.). Some disadvantages arise by this method: - offline transfer takes a long time - incompatibility of peripheral devices, storage medium and dat a representation can make file transfer impossible or lead to an additional overhead - for step A and C the user must be familiar with the control languages of every participated operating and file management system - additional operations on the transferred file must be organised under the system control of the destination host A lot of advantages offers a File Transfer Service, integrated in a network, which links together the above mentioned computer systems (hosts): - with a reliable transport system in the network a fast online transfer of the file data can satisfy step B - step A and C are controlled by the File Transfer Service with only one standard interface to the user - additional operations on the copied file can he managed during the transfer of the data (conversion of file structure, file dat a and subsequent operations e.g. print) - peripheral device support by involved operating and file management system under File Transfer Service control The HMINET is a private star-shaped, heterogeneous network, which connects 22 process control computers and 3 mainframes. One basic function in that computer network is such a file transfer service. Typical applications of this service are: Copy of data files from and to mainframes and process control computers Transfer of programms and runable modules Remote Job Entry and remote spool services, etc.