Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!nosc!ucsd!ucbvax!VAX.FTP.COM!jbvb
From: jbvb@VAX.FTP.COM (James Van Bokkelen)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: Sharing Interfaces
Message-ID: <8807281728.AA05143@vax.ftp.com>
Date: 28 Jul 88 17:28:12 GMT
References: <8807280741.aa23266@Louie.UDEL.EDU>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 40

When Phil Karn, Russel Nelson, Karl Auerbach or I (at least) say "Packet
Driver spec", we mean the one FTP Software has published.  3Com calls their
linked-in libraries "3L", and the upcoming Protocol Manager spec "MAC/Vector".
I haven't heard anything about Novell's, let alone a name.

FTP's Packet Driver spec does allow multiple interfaces in a machine, but
only one per interrupt.  The spec says that you are supposed to scan a
range of vectors, looking for one that points at a JMP followed by a
particular string.  If you don't like the one you find, or want more than
one, you can keep on scanning.  The only limit on the number of vectors
is the size of the range you scan (32 vectors, 0x60 to 0x7F).

3Com/Microsoft have lots of clout, but the MAC/Vector interface is not
on the streets yet.  Furthermore, it had several aspects that I consider
severe problems the last time I looked (it was being actively revised as
of May).

 1. You do all of your binding (setting up handlers for incoming packets)
 at CONFIG.SYS time, so you can't use many DOS (or OS/2) services while
 starting your protocol modules.

 2. You cannot un-bind, ever.  No transient network protocols built into
 programs, no un-loadable protocol TSRs.  Instead, you have to edit a file
 & reboot if you need more memory to run your CAD program or whatever....

 3. Rather than telling MAC/Vector what kind of packets you want, instead
 it goes down its list of handlers, asking them one after another "do you
 want this packet".  This means that there is no possibility of arbitration
 (or even error detection) when two applications want the same type, and
 opens the door for "badly behaved applications" to screw things up for
 the rest of us.

The Packet Driver spec has some problems, too, but it can and will be revised
(with input from many people using it in different ways) while remaining
backwards compatible.  MAC/Vector might be revised as well, but I don't think
I'll see any of my objections dealt with (except maybe a one-shot 'unbind',
with no possibility of a 're-bind'); the others seem pretty organic to the
design of the thing.

James VanBokkelen
FTP Software Inc.