🚀 go-pugleaf

jack@robotics.jpl.nasa.gov (Jack Morrison) writes:
+---------------
| I'd appreciate suggestions for a protocol between two devices connected
| by 9600 baud R/F modems. Here are the constraints:
| * Not too complicated. One side is driven by an 8-bit CPU.
| * Good error detection required (e.g. 16-bit CRC). Correction can be
| 	by retransmission.
| Things I've considered, and why I'm still looking:
| * DDCMP - still too complicated
+---------------

*BZZZZT!!*  Way back circa 1974 at DCA, we were doing DDCMP at 9600 baud on
a slow Z80, *and* multiplexing a bunch of terminals on to/off of the link.
DDCMP's a *simple* protocol, as window-oriented error-correction-by-retrans-
mission protocols go. Just about any idiot can implement it directly from the
spec and get it right. (Why, we were shipping it two years before DEC did!)
Seriously, you're not going to find anything much simpler that meets your
stated goals.

+---------------
| * SLIP - the IP part seems like overkill
+---------------

(*sigh*) This one again... Please go read Michael Padlipsky's classic paper,
"Slaying the TCP-on-a-LAN Woozle" (Chapter 7 in "The Elements of Networking
Style"), which tried to put one to rest decades ago (Santayana explained why
it didn't succeed):

        ABSTRACT: The sometimes-held notion that the DoD Standard
        Transmission Control Protocol (TCP) and Internet Protocol (IP)
        are inappropriate for use "on" a Local Area Network (LAN) is
        shown to be fallacious.

For "LAN", substitute "packet radio". The argument still holds up.

+---------------
| Sure, I could make up a simple packet format and protocol, but I'd have
| to convince myself (and others) it worked properly under various error
| conditions. Besides, I'd prefer adopting (or buying) well-tested code -
| I've got plenty of other stuff to write.
+---------------

Well, the radio amateur community seems to like "AX.25" (not quite the same
as "X.25"), and many even run IP on top of it (with "KISS", a SLIP-like thing).
There are several kinds of amateur packet-radio software readily available,
some of which (e.g., the TCP/IP/KISS/AX.25 "NOS" of Phil Karn, KA9Q) can even
be licensed at reasonable rates for commercial use. Browse around newsgroup
rec.radio.amateur.packet for a while...


-Rob

p.s. For amateur, experimental, educational, or non-commercial use, you
can pick up KA9Q's "NOS" via anon-FTP from ucsd.edu:/hamradio/packet/ka9q
(sources & binaries). It will run on an 8088, or can be easily ported to
just about anything with a C compiler for it.

-----
Rob Warnock, MS-9U/510		rpw3@sgi.com
Silicon Graphics, Inc.		(415)390-1673
2011 N. Shoreline Blvd.
Mountain View, CA  94043