Re: Connecting to Ethernet

[dempson@actrix.gen.nz (David Empson)]

Toby Reiter <str4552@OBERLIN.EDU> wrote:

> There was a recent discussion in comp.sys.apple2 about methods for 
> connecting a IIgs to ethernet, and a lot of people proposed extremely
> complicated and expensive solutions. One thing that I have seen here at
> my college (Oberlin) has really piqued my curiousity. It is a cable which
> connects to a serial mini din8 port, ends in what looks like a rs232 
> serial connection (male I guess) which is then attached to a female rs232
> which then become a ethernet, cable and is plugged into an ethernet port
> on the wall. Does anyone know what this thing is, and could it be used
> with a IIgs?

What is it connected to at the moment?  A Macintosh or something else?

What sort of Ethernet port is it?  I assume it is a 10Base-T (UTP)
connection, i.e. an RJ-45.

Is there any kind of box in the middle of the cable?  If not, I cannot
see any way that this could possibly work as described.

Ethernet requires a 10Mbps serial connection with electrical
characteristics that vary according to the cabling system.  The Mac
serial port is not able to support this data rate, let alone meet the
electrical requirements.

The most likely explanation is that what you take to be an Ethernet port
is actually a LocalTalk connection.  This would go to a bridge or router
which converts it into Ethernet (this can be done in software on a Mac
with LocalTalk and Ethernet support).

The Mac plugged into the cable would be using the AppleTalk protocol
stack over the connection.  This would allow it to access devices that
are using EtherTalk (AppleTalk running on Ethernet).  It could also be
running TCP/IP, with the packets encapsulated using MacIP, which runs
over AppleTalk.  This would allow access to devices on the Ethernet
which are using TCP/IP.

> Also, does anyone know if Macintosh servers can be accessed over an 
> EtherTalk network? This would be nirvana for me, if this could be done.

I assume you mean from a IIgs.

Definitely, given an appropriate router between the IIgs LocalTalk
segment and the main EtherTalk backbone.  The EtherTalk and LocalTalk
segments may be set up different zones on the AppleTalk network, but
that doesn't complicate things much.

If a simple bridge is used between the LocalTalk and EtherTalk segments,
then they will appear to be part of the same zone, and it is even easier
to access the server.


Furthermore, if the IIgs was running GS/TCP and the bridge is a Mac
running MacIP, then the IIgs would be able to access TCP/IP devices on
the Ethernet by transmitting encapsulated IP packets over AppleTalk.
(I'm not sure how this works in detail, as I've never seen a MacIP
setup.)

-- 
David Empson
dempson@actrix.gen.nz
Snail Mail: P.O. Box 27-103, Wellington, New Zealand