Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-lcc!ames!ncar!mailrus!ulowell!bbn!bbn.com!denbeste
From: denbeste@bbn.com (Steven Den Beste)
Newsgroups: comp.sys.amiga
Subject: Bitnet FTPs
Message-ID: <34568@bbn.COM>
Date: 16 Jan 89 01:35:23 GMT
Sender: news@bbn.COM
Reply-To: denbeste@BBN.COM (Steven Den Beste)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 40

OK, I know this isn't about the Amiga, but the question was asked here, and
it'll probably come up again. I've mailed this to people more than once, so I
thought I'd post it this time.

There isn't any way for someone on Bitnet to FTP to an Internet site. The
reason has to do with the kind of gateways that are between the Internet and
Bitnet.

The Internet is held together with X.75 gateways and other ones which perform
similar functions. The point is that these gateways operate at ISO level 3, so
they are transparent to ISO level 4 protocols. ("mail" is a level 4 protocol.
FTP is another, and it isn't compatable with mail.) So anyone in the Internet
can FTP to any other site through one or more gateways, and never know it
(except that perhaps the performance suffers a bit and subject, of course, to
security considerations).

The Internet/Bitnet gateways are "mail gateways" - they operate at ISO level 4,
and thus are not transparent to the originating machines. More importantly,
they impose a protocol on the data at level 4: "mail". FTP cannot pass through
them. (I might mention that the level 4 gateways in question also batch: there
can be a long time - minutes or hours - between when the data arrives at the
gateway and when it leaves. By comparison, the latency of an X.75 gateway
is typically measured in milliseconds.]

[Also by the way, ISO level 4 is not invisible to the user. You Bitnet folks
have probably noticed that you have to send mail to the Internet through
some Bitnet machine like 'cunyvm'. Well, 'cunyvm' is one of the mail gateways,
and I gather that 'udel' is another.]

Within Bitnet, users should be able to use FTP just fine. But until and unless
someone installs a level 3 gateway between the networks, FTP across the
boundary is not possible.

[By the way, if someone knows differently about this, I'd sure like to know
about it.]



Steven C. Den Beste,   BBN Communications Corp., Cambridge MA
denbeste@bbn.com(ARPA/CSNET/UUCP)    harvard!bbn.com!denbeste(UUCP)