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From: liam@cs.qmw.ac.uk (William Roberts)
Newsgroups: comp.protocols.appletalk
Subject: Re: A Mac to Unix File System (like NFS)
Summary: No kernel mods for CAP or UAB
Keywords: CAP, UAB
Message-ID: <1732@sequent.cs.qmw.ac.uk>
Date: 2 Mar 90 11:08:05 GMT
References: <1990Feb26.212826.13117@uunet!unhd> <1990Feb27.130756.1343@uunet!unhd> <1716@sequent.cs.qmw.ac.uk> <6467@ncar.ucar.edu>
Reply-To: liam@cs.qmc.ac.uk (William Roberts)
Organization: Computer Science Dept, Queen Mary and Westfield College, U of London, UK.
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In article <6467@ncar.ucar.edu> hpoppe@bierstadt.scd.ucar.edu (Herb Poppe) writes:
>
>Is UAB implemented as a kernel mod or otherwise require kernel mods?
>Is CAP implemented as a kernel mod or otherwise require kernel mods?

CAP is implemented on top of the Berkeley sockets stuff and so
needs no kernel modifications. UAB is written (for SunOS 4.0 at
least) on top of something called NIT (network interface tap)
which is a way that the superuser can receive copies of any
Ethernet packet addressed to thsi machine, into a user-level
process. This also requires no kernel modificiations by the
person installing UAB, but you do of course need a kernel which
has the network tap stuff which is why UAB only works on a few
machine types.

Technophiles may be interested to know that the Sun versions of
the network tap is a streams clone device, and useful streams
modules include a packet filter (presumably used to receive
only the EtherTalk packets and ignore all the IP and ARP
stuff), a buffering module with some annoying semantics, and a
"turn this stream back into packets" module! :-)
UAB requires SunOS 4.0 because the SunOS 3.x version of NIT
didn't work properly and was completely rewritten.

I believe that some kernel implementations based on the BSD
protocol switch mechanism are available: Kinetics do (did?) a
commercial one which was licenced by Sequent for the Balance
(but long before EtherTalk got properly sorted out), and I
think that there's even an academic licence one available
somewhere. Anyone out there got more details on these?
-- 

William Roberts                 ARPA: liam@cs.qmw.ac.uk
Queen Mary & Westfield College  UUCP: liam@qmw-cs.UUCP
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