ETHRAX25 - Ethernet to AX.25 Packet Driver
			   Revision: 940530
			     30 May 1994


ETHRAX25 is a modified version of the ETHERSL packet driver from the
Crynwr collection.  It provides an Ethernet (Class 1) interface to the
application,  and produces AX.25 UI frames, encapsulated in KISS on a
serial port.

Outgoing Ethernet frames are converted into AX.25 Unnumbered
Information (UI) frames.  The application sees pseudo-Ethernet
addresses which are an encoded representation of the AX.25 address.
The AX.25 frame is then encapsulated in KISS framing and sent on the
specified serial port to a KISS-mode TNC.

The reverse is done for incoming KISS frames, which are converted to
pseudo-Ethernet frames for the application.

If the frame contains an ARP packet, the driver translates the hardware
addresses between AX.25 address and pseudo-Ethernet addresses as
needed.  Thus ARP works transparently.  The Ethernet broadcast address
ff-ff-ff-ff-ff-ff is converted to the AX.25 broadcast address QST-0 and vice
versa.

Usage:

The driver is loaded in the same fashion as other packet drivers.
The parameters are:

ETHRAX25 <packet_int_no>  [-h] [hardware_irq] [io_addr] [baud_rate] 
	[send_buf_size] [recv_buf_size]

-h enables hardware handshaking on the serial port.

Since the application believes it is talking to an Ethernet, there are
some AX.25 and TNC parameters which must be set before the application
is started.  These are set using the AX25CONF utility:

AX25CONF <packet_int_no> [-stat] [-mycall <ax25 addr>]
			 [-txdelay n] [-persist n] [-slottime n] [-txtail n]

Where:
	<packet_int_no>  -- the interrupt number for the packet driver
	-stat		 -- reports driver statistics
	-mycall ax25addr -- sets the AX.25 address (callsign with
			    optional SSID)
	-txdelay n	 -- sets the TNC's txdelay (10 msec units)
	-persist n	 -- sets the TNC's p-persistence
	-slottime n	 -- sets the TNC's slottime (10 msec units)
	-txtail n	 -- sets the TNC's txtail (10 msec units)


If the driver is being used with a MS Windows application, remember to
load the WINPKT driver after loading ETHRAX25.

Caveats:

The current version of the driver has been tested with a small set of
DOS and Windows applications.

Under DOS, the driver has been tested with WATTCP (7/16/93 vintage)
and Kermit 3.13 at 9600 baud.  However, since both of these IP stacks are
tuned for Ethernet or fast serial links, they are not useable over
1200 baud radio links.  The driver was tested by connecting the serial
line to a system running KA9Q NOS, which was configured as if
connected to a KISS TNC.  Ping, telnet, ftp, and DNS seem to work.

Under Windows, the driver has been tested with the Trumpet Winsock TCP
stack, Version 1.0 A.  The overhead introduced by Windows causes packets to be
dropped when running the serial line at 9600 baud.  This can probably
be fixed by using a serial port with a 16550 UART.  The line works
reliably at 2400 baud.

The driver was tested running the Trumpet newsreader, the ping,
hopcheck, telnet, and ftp utilities that come with Trumpet Winsock,
and WS_FTP.  All of these "worked" over a 1200 baud radio link.  I put
"worked" in quotes because, while there don't appear any
driver-related problems, Trumpet Winsock TCP stack appears to have
some quirks which surface when running over something that slow.

The WS_PING utility (931003) always gets a fatal error, but that sometimes
happens when running over Ethernet as well.

Other protocols which pass hardware addresses (like BOOTP) probably
won't work without explicit support in the driver.

The assembler code was assembled with Borland TASM 2.0.  The C code was
compiled with Borland C++ V2.0.