The notion of allowing continuation lines to start with arbitrary text solves a minor problem for a few server FTP implementors at the expense of creating a major problem for all user FTP implementors. This hardship is somewhat easily solved on a machine that has hardware stacks, but not so for other machines. The prose descriptions of the meanings of the various reply codes are in several cases unclear or ambiguous. It is given as a reply that can be issued when a server cannot accept input immediately after an ICP, but its exact meaning is not obvious. A major complaint about the protocol concerns the fact that the writer of an FTP user process must handle a considerable number of special cases merely to determine Whether or not the last command sent was successful.
Different commands have different success reply codes.
The meanings of the various connection greeting reply codes are somewhat inconsistent. It is however unlikely that notification of an expected delay would be of importance to a user Process without knowledge of the length of the delay.