Path: utzoo!mnetor!uunet!husc6!mit-eddie!ll-xn!ames!umix!umich!mibte!gamma!pyuxp!pyuxww!sabre!faline!karn
From: karn@faline.bellcore.com (Phil R. Karn)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: Re: usage of KA9Q package with async modems
Message-ID: <1703@faline.bellcore.com>
Date: 12 Jan 88 00:02:41 GMT
References: <1028@vsedev.VSE.COM> <8801091906.AA19617@spdcc.COM>
Organization: Bell Communications Research, Inc
Lines: 29
Summary: slip in KA9Q package

> I have been told that the encapsulation that KA9Q
> uses on packet radio is essentially SLIP, so all you'd need to do is install
> a serial asynch driver.  Don't try to use the serial handling in the BIOS,
> it is way too slow and flakey...

The KA9Q package supports the same SLIP that everybody knows (and
loves?) There is no support for dialing a modem; this has to be done by
first running a separate (e.g., PROCOMM) and then bringing up net.exe.

The packet radio encapsulation you mention is a special use of SLIP that
is actually used only between the host PC and an external radio
interface box called a "TNC" (Terminal Node Controller) that has been
reprogrammed to operate as a simple asynch/synch frame format
translator. (We call this the "KISS TNC" as an editorial comment on the
everything-including-the-kitchen-sink firmware that normally runs on
TNCs). The protocol actually spoken on the air is synchronous HDLC,
complete with flags, bitstuffing and CRCs.  The frame headers are unique
to amateur radio, however; they carry our amateur radio callsigns as
link level addresses.  Somewhat simplified, the frames look like this:

___________________________________________________________________
FLAG|Dest Callsign|Source Callsign|CTL|TYPE=IP|IP datagram|CRC|FLAG
-------------------------------------------------------------------
        7 bytes       7 bytes       1     1      variable   2

The resemblance to Ethernet encapsulation was intentional. We even use ARP
to resolve IP addresses to callsigns.

Phil