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From: jbvb@FTP.COM (James B. Van Bokkelen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: TCP/IP via Token Ring
Message-ID: <9103081532.AA26454@ftp.com>
Date: 8 Mar 91 15:32:17 GMT
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Reply-To: jbvb@ftp.com
Organization: The Internet
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Some history: Long ago (1986 or so), when IBM first shipped 802.5 cards
for the PC, they defined a standard software driver (very much like the
Packet Driver in concept) which all protocol stacks and applications
could use, and thus be hardware-independent.  The spec was entitled
"Adapter Support Interface", and was initially implemented in
TOKREUI.COM (various versions for the different IBM 802.5 adapters).
In order to work with IBM's applications, all the other 802.5 board
vendors implemented ASI drivers, too (PRO4EUI, 3COMREUI, etc.).

So, there is very little software out there which has board-specific
drivers for 802.5 (our LANWatch uses direct-to-the-board interfacing
with Proteon hardware, because ASI doesn't support "match all" as a
security measure).  PC/TCP, Netware, Vines and pretty much everything
else prefers to use the ASI driver (normally IBM's LAN Support Program,
which replaced TOKREUI a few years ago).  Because it is ubiquitous,
we could ship one part for 802.5 where we ship 20 for different
Ethernet boards, and this is very attractive...

The IBMTOKEN Packet Driver uses ASI to talk to many vendors' hardware,
but keep in mind that it is a Class 1 (DIX Ethernet) driver, which
adds the necessary RFC 1042 framing so the protocol stack doesn't have
to be 802.5-aware.  This is good for limited use of DOS TCP/IP stacks
that don't happen to be available in 802.5-aware versions (the free
ones).  However, it breaks down under heavy use (ARP cache in the stack
conflicts with RIF cache in IBMTOKEN) or when you're trying to use
protocols that don't use the same Ether -> 802.5 transform as TCP/IP.

Recently (1990), IBM introduced NDIS drivers as an alternative to the
LAN Support Program, but not many DOS products can use an NDIS driver
for 802.5 yet.  Some of the board vendors have followed suit, but what
I've heard about IBM's own statements of direction indicate that both
ASI and NDIS will continue to be supported in parallel for a while.

James B. VanBokkelen		26 Princess St., Wakefield, MA  01880
FTP Software Inc.		voice: (617) 246-0900  fax: (617) 246-0901