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Re: Marinetti over LocalTalk/Appletalk?
In article <f6ab8a2f.0202172112.32057547@posting.google.com>,
andrew.roughan@writeme.com (Roughana) wrote:
> Thanks very much for your analysis and input.
> I'm learning a lot about Appletalk.
>
I hope it helps! :)
> jalapeno1@mac.com (jalapeno) wrote in message
> news:<2f367031.0202150833.538c138b@posting.google.com>...
> > We can write our own IP Gateway if you have a LanceGS card.
> > IP Gateways are easy (famous last words ;) to program and the
> > MacIP docs tell you what you need to include.
> I believe that the LanceGS comes with it's own Link Layer for
> Marinetti.
> So this is probably not necessary.
> Would anyone with a LanceGS care to comment?
>
The LanceGS does come with its own link layer and that would be needed
for a MacIP gateway. One possible block diagram for a IIGS IP Gateway
would be (off the top of my head):
+---------- begin ascii art -----------+
+--------------------------------------+
| IIGS |
| |
| +--------------+ +--------------+ |
| | | | | |
| | Marinetti | | Appletalk | |
| | TCP/IP stack | | stack | |
| | | | | |
| +----o----o----+ +--o----o------+ |
| | \ / | |
| | \ / | |
| | +--o-----o--+ | |
| | | IIGS | | |
| | | IP | | |
| | | Gateway | | |
| | | | | |
| | +-----------+ | |
| | | |
| | | |
| LanceGS Localtalk |
| ethernet builtin |
| card port |
| | | |
+------O---------------------O---------+
| |
Z Z
| |
ethernet Localtalk
network network
| |
Z Z
| |
+---------- end ascii art -----------+
Marinetti would be the gatekeeper for the ethernet network and the built
in Appletalk stack would be the gate keeper for the Localtalk network.
The IIGS IP Gateway software would install socket listeners (a DDP
[datagram delivery protocol] socket listener on the Appletalk stack and
an IP socket listener on Marinetti) to watch for traffic on both
networks.
When a MacIP packet comes in on the Localtalk network then the IIGS IP
Gateway program would strip off the DDP header and send the remaining IP
datagram to the ethernet network via Marinetti.
When an IP datagram comes in via the ethernet network the complete IP
datagram that Marinetti stripped from the ethernet packet would be sent
to the IIGS IP Gateway software which in turn adds a DDP header and
sends it to the Localtalk network.
If the destination on the Localtalk network is another IIGS then that
IIGS would have its own Marinetti with the MacIP link layer running and
(the local copy of) the Marinetti link layer would strip off the DDP
header from the IIGS IP Gateway and Marinetti would process the IP
datagram in the usual fashion.
I don't know how Marinetti functions but the DDP socket listener will be
called via an Appletalk interrupt (this is handled by the firmware and
the Appletalk driver). If Marinetti doesn't operate via interrupt then I
suppose you'd need a tight loop to poll for IP datagrams.
So I guess (again, off the top of my head) one possible algorithm for
the IIGS IP Gateway would be (omitting all error checking and
implementation details):
1. At launch check for Appletalk and Marinetti being installed and
active. (from here on assume they are)
2. Register on the Localtalk network as an IPGATEWAY (following the
normal Appletalk NBP registration sequence with the addition of an ATP
socket listener so new IP addresses can be assigned when new MacIP nodes
come active).
3. Broadcast on the Localtalk network for any entities registered as
Object type IPADDRESS. If any respond add their Appletalk node and IP
address to the translation table. This might need to be done prior to
step two but this is the order it came to me :)
4. Wait for appropriate network traffic.
5. Add DDP headers to ethernet traffic going to MacIP Localtalk nodes
and send it to the Localtalk network. This includes extracting the IP
address and converting it to ascii and adding it as the Object name
(without the period separators) in the DDP header.
6. Strip DDP headers from Localtalk traffic coming from NVE's of Object
type IPADDRESS and send it to Marinetti.
7. Rinse and repeat 4-6 :)
> > With a IIGS IP Gateway you can get rid of your
> > Powerbook and IPNetRouter all together :)
> The idea behind my investigation is to get a solution working that
> uses MacIP across Appletalk to something. This will allow the
> documentation of the solution for others who may have this gear
> available to them.
>
Yes, I understood. But why stop there? Think BIG! :)
> > Ok, it sounds like IPNetRouter is using your Mac's OpenTransport or
> > MacTCP client to send via Localtalk.
> I am using OpenTransport with MacOS 8.1.
>
> > Do you have a Localtalk packet sniffer?
> No. I have searched for one in software for the Mac.
> LocalPeek does not seem to be available anywhere. Broken links
> everywhere.
>
> > Actually, a IIGS packet sniffer shouldn't be hard to write (famous last
> > words again) since LLAP is built into the firmware.
> Would this need to sit on a second IIgs on the Appletalk network
> or on the same IIgs as Marinetti?
>
This would have to be on your $0.99 IIGS that you picked up off of ebay.
Unfortunately the Localtalk Link Access Protocol (LLAP) rejects packets
that do not have it's node id in the LLAP packet header and since it
uses a circular buffer you have to be very quick to get the packet
before it is overlayed. My first thought is to have a very tight loop
issuing LAP readbuffer calls and copying out the data but that might not
work if the firmware only operates on valid packets for this node. In
that case it'd be more difficult but still should be doable.
> Cheers,
> Andrew