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1995-06-25
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ARCEther Packet Driver:
Novell 3.11 servers now have the possibility to route IP packets and to send
IP traffic over ARCnet. The protocol numbers and framing types these servers
use on ARCnet are described in RFC 1201. Because there is actually no packet
driver which supports this framing, we decided to change the existing ARCNET
packet driver so that it supports the standard described by RFC 1201.
Since there exists hardly any free software which supports ARCnet type packet
drivers, we decided two show up for applications as Ethernet class 1 driver
and transform Ethernet to ARCnet packets and vice versa within the driver.
This includes splitting and reassembling packets on ARCnet since Ethernet
packets can be 1500 bytes long while the maximum size for single ARCnet
packets is 504 bytes.
Since you certainly don't want to log off from your network and reboot the PC
to use Telnet of FTP, the driver has to support Novell IPX packets as well. So
if you have the BYU IPX Shell, ARCEther allows you to work within your Novell
Network and at the same time use TCP/IP products written for Ethernet packet
drivers.
The usage of ARCEther is straight forward. If you start the program without
any command line parameters, it tells you
usage: arcether [-n] [-d] [-w] <packet_int_no> <int-no> <io_addr> <mem_base>
The "packet_int_no" is the interrupt number through which apllications can
access the packet driver.
"int_no" is the IRQ your ARCnet card uses. Don't be afraid if you enter 2 and
the driver tells you that is uses int_no 9, thats okay.
"io_addr" is the port through which the packet driver can communicate with the
ARCnet card and is determined by the jumper settings on the card.
"mem_base" is the segment of memory which the ARCnet card uses.
The option -w and -d are the same as for all packet drivers.
-d tells the driver to delay the initialization of the ARCnet card until
the first request arrives. You must start the driver with this this
option if you boot your PC from the network because otherwise the Boot-ROM
cannot load the IPX-Shell.
-w tells the driver to use the window option
The -n option is for ARCEther a very special option and has not the same
effect as for standard Ethernet packet drivers. If you use the -n option,
ARCEther assumes that it should build and expect Novell 802.3 packets instead
of Novell Bluebox packets. You should therefore use this option with the 1991
version of the IPX shell which sends and receives 802.3 packets. If you have an
older version of the IPX Shell, do not use the -n Option.
Another effect of the -n option is that the driver does not refuse requests
for a class 11 driver when you use this option since the new IPX-Shell
requires such a driver. Please remember that ARCEther is not really a class 11
driver and may hang your PC if other programms than the IPX-Shell access it
via class 11.
There is one possible difficulty which the driver can't handle: The Server
does not access the ARCnet hardware through ARCEther but has its own TRXNET
driver. So Novell Servers may send packets which consist of more than 3
fragments or are longer than 1500 bytes. ARCEther cannot handle such packets
because it cannot request such a buffer from a client and simply does not
deliver such packets to any client application.
We tested ARCEther on our own Network and noticed that our Novell 3.11
Server never used such long packets, but maybe there are situations in which
Novell very uses long packets since Novell's TRXNET Driver supports a maximum
frame sze of 4602 bytes.