Subject: Ftp-WG: HOST command and client upgrades

From: "Jan Mikkelsen" <[email-masked]>
Date: Mon, 25 Oct 1999 18:44:25 -0400

D. J. Bernsten writes:
[ HOST vs. EPLF, transition plans]

When comparing HOST, as specified, and EPLF, I can see your point.  As I
have mentioned elsewhere in this thread, an overloaded USER argument gets
you virtual hosting without breaking old clients.

But let's put that to one side, and look at HOST as specified:

-  If servers don't force clients of a particular level to support HOST,
even when they don't support virtual hosting, I am concerned that it won't
be implemented widely enough, ever.

-  It is difficult to detect exactly what the client base supports without
some extra information.  With HTTP, you can can use the version numbers.
You don't have any such luxury in FTP.

These also hold for EPLF.  The differences are

-  It is hard to have a method of using EPLF during the transition phase to
measure how many clients support EPLF, so that a switchover decision can be
made.  With a separate command during the transition phase, an operator can
say "99% of directory listings against my server used EPLF.  I can switch."
Otherwise they are just stabbing in the dark;  bugs in clients haven't been
exercised.

-  After the "Great Switchover", an old client with work against a server
which does not use virtual hosting, but it will potentially fail against one
that uses EPLF.

Jan Mikkelsen