Re: Protcol Development on SUN 2 and 3 computers.


Steve D. Miller (steve@brillig.umd.edu)
Tue, 16 Dec 86 08:30:23 EST


   The Sun networking implementation is very close to being identical to
the standard 4.2BSD implementation. Unfortunately, that makes development
of other protocols (unless they live on top of IP, in which case it's
not bad to do) more troublesome than you might expect as, if memory
serves, the networking implementation manual (also lifted from a 4.2BSD
manual) is incorrect (or, perhaps, misleading) in terms of talking
about its protocol independence. There are all sorts of nasty AF_INET
dependencies lurking about in there, everywhere from the device drivers
to the network interface and routing code to NFS. It is possible to
track all these dependencies down -- Chris Torek and James O'Toole
did it here when they did their Xerox NS implementation for 4.2BSD --
but it probably won't be a whole lot of fun to do.

   Back under Sun Unix 2.0 I hacked some XNS support into the kernel.
The way I did it was to remark, "gee, the interface between the network
code and the rest of the kernel isn't so bad" and stuff the whole of the
4.3BSD beta networking code into the kernel, throwing the Sun/4.2BSD code
out. Depending on what you're doing, that may be a win. I believe
that it was for me, as I didn't have to write a NS implementation if
I worked it that way. Furthermore, changing the INET-dependent code
is probably not particulary hard, but you'll have to muck with the
innards of almost every kernel module in /sys/net*, and that could
be both tedious and frustrating. Finally, the 4.3BSD networking
implementation is very much improved over the 4.2BSD one in the area
of TCP/IP, so you get a better TCP/IP in the bargain.

   Oh yes, and of course it looks easier to stuff an entirely new
(non-INET, non-NS) protocol into 4.3BSD than it does into 4.2BSD.
There can't be too many dependencies still lurking about, 'cause
the NS support works.

   Hope this is of use to you.

        -Steve

Spoken: Steve Miller ARPA: steve@mimsy.umd.edu Phone: +1-301-454-4251
CSNet: steve@mimsy.umd.edu UUCP: {seismo,allegra}!mimsy!steve
USPS: Computer Science Dept., University of Maryland, College Park, MD 20742



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