Subject: [netatalk-admins] Re: Netatalk works quite transparently:
From: Justin C. Walker (justin@apple.com)
Date: Mon Jul 05 1999 - 23:44:53 EDT
> From: Heinz Nabielek <h.nabielek@fz-juelich.de>
> Date: 1999-07-05 01:44:23 -0700
> To: linux-pmac@samba.anu.edu.au,
> mklinux-setup@public.lists.apple.com,netatalk-admins@umich.edu
> Subject: Netatalk works quite transparently:
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>
> Netatalk works quite transparently:
As does AppleTalk. The only tricky part is configuring routers.
[snip]
>
>
____________________________________________________________________________
> _____
>
> What puzzles me, are the Appletalk network numbers
> 65280.5=FF00/05hex
> 41201.173=A0F1/ADhex
Apple represents AppleTalk network addresses as decimal: 16 bits
(unsigned) for network number and 8-bit (unsigned) for node number.
> Linux tcpdump shows
> "aarp probe 160.241.173 tell 160.241.173"
> and I note
> 160x16^2+241=41201.
>
> On Linux, /etc/atalk/afpd.conf is
> server1 -port 12000
> server2 -port 12001
> server3 -port 12003
>
> and /etc/atalk/atalkd.conf
> eth0 -phase 2 -net 0-65534 65280.5
> whereby the last item fixes the Appletalk
> network address on the linux box.
>
> But- how do I fix the Appletalk address
> on the MacOS side?
I'm not sure what you mean by "fix". Looks like there's a bit of
inconsistency in network number representation on non-Mac boxes:
sometimes it's 16-bit unsigned decimal, sometimes, it's a pair of
8-bit unsigned decimal numbers (e.g. "tell 160.241.173": the first
number is the "high" byte of the network number; the second, the
"low" byte; and the third is the node number).
> 65280.5 was the linux box' address under MacOS.
>
> Who dishes out these numbers in the first place?
Unlike the IP world, the AppleTalk world is "self-defined". There
is no IANA/ICANN to assign network numbers, and there's no
presumption that network numbers are unique world-wide. That's why
joining previously separate AppleTalk internets is such a joy.
Starting from the simple case: no routers means that each system
decides for itself what its network number and node number is. There
is a predefined range of network numbers called the startup range.
Check Inside AppleTalk (which I don't have with me right now) or the
code for the exact range. Something in the high 16-bits. Without a
router present, a newly booted AppleTalk node selects a network
number from this range. Then it sends out a probe (AARP) with its
chosen network number and node number, asking if anyone's seen this
one. If yes, it chooses another node number and proceeds. If no,
that's its address.
Life is similar in the presence of routers, except that after a
successful "defense of address", a packet is sent out asking for
network information. No router means no response; if there's a
router, it responds with the "cable range" of network numbers, and
the address defense begins again, as above, but with a new network
number. Eventually this converges, or all addresses are taken (and
the cooperative node won't partake in AppleTalk).
Network number assignment, outside the startup range, is in the
hands of the sysadmins who administer the routers. So-called
seed-routers distribute network numbers to attached network segments.
It gets really complex at this point, but the effective answer to
your question is:
- no routers -> each node decides its address and defends it
- routers -> a more complex environment, and network number
assignment is in their hands (although the effect on individual nodes
is just another round of defense; typical nodes cache their address
in NVRAM/PRAM to simplify life, but the cache is really only a hint:
between reboots, another node could end up with your address).
Hope this helps, and wasn't too involved.
Regards,
Justin
-- Justin C. Walker, Curmudgeon-At-Large * Institute for General Semantics | Manager, CoreOS Networking | When crypto is outlawed, Apple Computer, Inc. | Only outlaws will have crypto. 2 Infinite Loop | Cupertino, CA 95014 | *-------------------------------------*-------------------------------*
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