Ftp-WG: NLST vs MLSD

Frank da Cruz writes:
> widespread if not universal server-side wildcard

Certainly not universal. High-quality clients don't rely on it. You are
overgeneralizing when you claim that NLST expands wildcards.

> You're overloading MLSD.  It is at once a new file-listing format and a
> new discipline to reduce load on the server -- two unrelated concepts.

The discipline is not new. If you want to handle wildcards, you should
be relying on the standard protocol that works with all servers, rather
than on the behavior of certain FTP servers. Load is a red herring; the
real issue is reliability.

> At some point, if only as a final resort, the user must be exposed to
> the server host's notation -- it can't be totally hidden without
> interfering with access.

False. For example, NFS and ftpfs users access files just fine without
having any clue about the server's favorite wildcard notation.

> We might consider it unlikely that a user might want to get 3 files out of a
> directory containing a very large number files, but that does not mean the
> protocol should ignore this case.  It's same argument that was made when
> designing the address space of the early networks, which was outgrown faster
> than any expert foresaw (more than once).

No, it isn't the same argument.

Obvious difference #1: Address limits are much more serious than speed
limits. Speed is multiplied by a renewable resource, namely time, while
addresses are not.

Obvious difference #2: Limits on the size of the entire system are much
more serious than limits on local branching factors. I don't care
whether I can put a million files into a single directory; I do care
whether I can put a million files onto a single disk.

> The server needs a way to suggest the
> appropriate STRU and TYPE for each file to the client.

No. It works much more smoothly to transfer a binary stream, along with
enough out-of-band information for the client to understand the stream,
as in HTTP. This is another good example of client-side processing being
better than server-side processing.

> FTP is used increasingly for transaction processing, EDI, etc (for
> example at IBM Info Exchange and Advantis).

Why? Do they have no clue how to design a sane protocol?

---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago