richb@dartvax.UUCP (09/18/87)
Folks:
Here's the situation with Async AppleTalk. I'm distributing the
DA, as well as the spec for AALAP and a bunch of other technical
information (including sources for the interesting parts of the
interrupt routines, etc.) Please send me a disk, and I'll fill
it up. Thanks.
Rich Brown
--------------------
What is Async AppleTalk?
Async AppleTalk is a Macintosh driver and desk accessory which allow a user
to access AppleTalk resources (file servers, laser printers, etc.) over a
dial-up RS-232 ("async") link. The driver replaces the standard AppleTalk
driver and intercepts the LAPWrite and LAPRead "hooks" to send or receive
the packets on an async link, instead of the 230.4 kbps AppleTalk Personal
Network (as it has been recently named).
Async AppleTalk presumes an (almost full) eight-bit data path. It works
with Xon/Xoff flow control. An escape mechanism allows arbitrary data
to be sent.
How can I use Async AppleTalk on my campus/office/home?
Ahah! Another person finds the problem! The answer is: you'll need some
other gadget to bridge between an Async AppleTalk and a high speed link.
Several commercial companies have announced hardware which will solve this
problem (Sand Hill Engineering, in Geneva FL, Solana Electronics in San
Diego, CA, Shiva Corporation, Cambridge, MA). Contact them for price and
availability information.
How do we use Async AppleTalk at Dartmouth?
We have a campus network with RS-232 ports which we have programmed to accept
Async AppleTalk messages from the Mac and sends them out an standard (230.4
kbps) wire. This makes file servers and laserwriters available to Macs which
have dialed in over Async AppleTalk. (AppleShare, LaserWriters, InterMail,
and a host of other utilities and public domain games work just fine...)
Is Async Appletalk compatible with all versions of the system software?
I have tested Async AppleTalk with Finder 4.1/Sys 2.0 and greater. I have
also used Async AppleTalk with a Mac/XL, 512K, 512Ke, Mac Plus, Mac SE and
Mac II. (I just received an alpha copy of multifinder, and will begin
compatibility testing soon.)
Is Async AppleTalk compatible with TOPS, MacServe and AppleShare?
Async AppleTalk works with AppleShare (the server must be on a 230.4 kbps
link). It does not work with TOPS 1.0 (TOPS expects a response much too
quickly. The 2.0 version may have fixed this.) It does not work with
MacServe (Async AppleTalk unregisters the names which MacServe registers on
startup).
Will it run on a Mac XL?
Async AppleTalk runs fine with a Lisa/Mac XL.
Can I use my XXX hardware with Async AppleTalk?
The answer is: sometimes. For a full answer, you need a bit of background:
There are two useful things to do with a box which has one AppleTalk port and
one async (RS-232) port. Async AppleTalk will do one, but not the other.
1. Async AppleTalk is designed to accept AppleTalk packets (which are
sequences of bytes in a predefined format) over a modem or other RS-232 link,
and to send them into an AppleTalk network as if the Mac were directly
connected. Thus, Async AppleTalk "replaces" a normal AppleTalk link with
a telephone link.
2. To connect your ASCII terminal or terminal emulator to an AppleTalk
network (for example, to share a modem) you need a device which accepts
single characters from an async device (the terminal), wraps them in an
AppleTalk packet, and sends them across the AppleTalk network. The
technical term for this is a Packet Assembler/ Disassembler (PAD). Async
AppleTalk does *not* do this. Don't worry, there are commercial
companies working on this, too.
You are correct to suspect that the same hardware could do these two
things (using different software). Within six months, I expect there will be
a lively market for boxes which perform both functions. If you already own
AppleTalk hardware, contact your vendor to see if they will offer these
capabilities.
How can I connect a LaserWriter (AppleShare, TOPS, etc ...)?
Today (July 1987), you probably can't. At Dartmouth we have modified our
entire campus network to work with Async AppleTalk and the 230.4 kbps
AppleTalk network. For most other institutions, it makes sense to wait a
bit for commercial implementations to appear.
When these commercial packages arrive, you ought to be able to plug the box
onto the standard AppleTalk wire, plug the modem in, and be off and running.
How is Async AppleTalk being distributed?
Dartmouth is distributing Async AppleTalk free of charge, with the following
conditions: we retain the copyright, so please keep our name on it, and
please don't charge money for it. Otherwise, feel free to use it or pass it
on to anyone else. If you want to use it in a commercial product, get a copy
of our distribution policy: it's included with a whole lot of other infor-
mation about Async AppleTalk. Send a disk in a mailer, and we'll send all
the information.
Has Async AppleTalk been implemented in a host computer??
No. I expect that Dartmouth will come up with such a package in the future
(we have no implementation schedule). This only gives one piece of the total
puzzle, though. For Async AppleTalk to be useful on a host, you'll need to
add many of the upper layer protocols (DDP, NBP, ATP, PAP, ASP, AFP, etc) to
provide real service. It is possible to think about grafting Async AppleTalk
into the Columbia AppleTalk Package (CAP) on Unix (CAP is freely available
from Columbia University), but it's a non-trivial implementation project.
On the other hand, if you'd like to work on something like this, please give
me a call. I'd love to make this happen soon.
---------------------------
Rich Brown
Manager of Special Projects
Dartmouth College
Kiewit Computer Center
Hanover, NH 03755
603/646-3648
EMail (CSNET, Bitnet, Usenet,...):
richard.e.brown@dartmouth.edu
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