Re: Apple IIGS network filesharing

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

Steven Nelson <steven-nelson@uiowa.edu> wrote:

> On Feb 9, 6:08 pm, demp...@actrix.gen.nz (David Empson) wrote:
> > Steven Nelson <steven-nel...@uiowa.edu> wrote:
> > > On Feb 9, 4:10 pm, dog_...@macgui.com (D Finnigan) wrote:
> > > > Steven Nelson wrote:
> >
> > > > > What is the reason that the OSX server doesn't respond to the IIGS
> > > > > Appleshare connect request, whereas OS9 seems fine with both?
> >
> > > > OS X uses AppleShare over IP, whereas OS 9 supports "traditional"
> > > > AppleShare.
> >
> > > I think this should be irrelevant because of the 'magic' of LocalTalk
> > > bridge which routes ATalk over localtalk and Ethernet.
> >
> > Nope. LocalTalk Bridge just forwards AppleTalk network layer protocol
> > packets (DDP) between LocalTalk and Ethernet, dealing with differences
> > in how AppleTalk addresses are handled on the two networks.
> >
> > AppleTalk packets travelling over Ethernet are a different Ethernet
> > packet type from IP and are not compatible with IP.
> 
> Thanks for the last two replies.  I am not understanding completely.
> A difference in ATalk packets I can understand.  Why do the iMacG4(s)
> show up as available file servers in the IIGS Appleshare cdev if the
> ATalk packets are different?

LocalTalk Bridge takes care of the packet differences between Ethernet
and LocalTalk.

The server appears on the IIgs because 10.4 still supports Name Binding
Protocol (NBP), which is the protocol within the AppleTalk stack that is
used to advertise and discover named services.

10.4 is advertising itself as an AppleShare server via AppleTalk (and
via other methods over TCP/IP), but only AppleShare clients which
support AFP over TCP/IP will be able to connect to it.

The TCP/IP advertising methods (Service Location Protocol and Bonjour)
are not supported by Mac OS 9, so 10.4 had to continue advertising
itself via NBP (AppleTalk) in order to support Mac OS 9 clients.

If you use a Mac OS 8 or 9 client with a Mac OS X 10.4 server, the
client will discover the server via AppleTalk but connect to it via
TCP/IP.

Older versions of Mac OS don't support AFP over TCP/IP, so they can't
connect to Mac OS X 10.4 either. I'm not sure of the exact cutoff - I
think 7.6 had AFP over TCP/IP client side as a standard feature but it
may have been available in the 7.5 era as an optional install. I got my
first Mac with 7.5.3 but wasn't working with servers until later.

> Failure comes at the login attempt where incompatible atalk would cause
> problems.  But why does the server appear if atalk is not working at some
> level?

The AppleTalk protocol stack is still supported by 10.4. Only one
component of it is missing: support for Apple Filing Protocol (AFP) via
AppleTalk.

I don't know offhand which of the other AppleTalk protocols are missing
from 10.4, but these high level ones are likely to be gone: AppleTalk
Session Protocol (ASP) is the basis for AFP-over-AppleTalk but it wasn't
used by any other core features; AppleTalk Data Stream Protocol (ADSP)
was never used by core features, only by third party applications.

The lower level AppleTalk protocols are there to support printing:
Printer Access Protocol (PAP), AppleTalk Transaction Protocol (ATP),
Name Binding Protocol (NBP), Datagram Delivery Protocol (DDP) and
various other minor ones such as echoing and AppleTalk router support.

-- 
David Empson
dempson@actrix.gen.nz