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WAN Router for Linux Operating System
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Version 1.0.0
December 31, 1996
Author: Gene Kozin <genek@compuserve.com>
Copyright (c) 1995-1996 Sangoma Technologies Inc.
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INTRODUCTION

Wide Area Networks (WANs) are used to interconnect Local Area Networks (LANs)
and/or stand-alone hosts over vast distances with data transfer rates
significantly higher than those achievable with commonly used dial-up
connections.

Usually an external device called `WAN router' sitting on your local network
or connected to your machine's serial port provides physical connection to
WAN.  Although router's job may be as simple as taking your local network
traffic, converting it to WAN format and piping it through the WAN link, these
devices are notoriously expensive, with prices as much as 2 - 5 times higher
then the price of a typical PC box.

Alternatively, considering robustness and multitasking capabilities of Linux,
an internal router can be build (most routers use some sort of stripped down
Unix-like operating system anyway).  With number of relatively inexpensive WAN
interface cards available on the market, a perfectly usable router can be
built for less than half a price of an external router.  Yet a Linux box
acting as a router can still be used for other purposes, such as firewalling,
running FTP, WWW or DNS server, etc.

This kernel module introduces the notion of a WAN Link Driver (WLD) to Linux
operating system and provides generic hardware-independent services for such
drivers.  Why existing Linux network device interface can not be used for
this purpose?  Well, it can.  However, there are few key differences between
typical network interface (i.e. ethernet) and WAN link.

Many WAN protocols, such as X.25 and frame relay, allow for multiple logical
connections (known as `virtual circuits' in X.25 terminology) over a single
physical link.  Each such virtual circuit may (and almost always does) lead
to diffrent geographical location and, therefore, different network.  As a
result, it is the virtual circuit, not the physical link, that represents a
route and, therefore, a network interface in Linux terms.

To further complicate things, virtual cuircits are usually volatile in nature
(excluding so called `permanent' virtual circuits or PVCs).  With almost no
time required to set up and tear down virtual circuit, it is highly desirable
to implement on-demand connections in order to minimize network charges.  So
unlike typical network driver, the WAN driver must be able to handle multiple
network interfaces and cope with multiple virtual circuits come into existance
and go away dynamically.
 
Last, but not least, WAN configuration is much more complex than that of say
ethernet and may well amount to several dozens of parameters.  Some of them
are "link-wide"  while others are virtual circuit-specific.  The same holds
true for WAN statistics which is by far more extensive and extremely useful
when troubleshooting WAN connections.  Extending ifconfig utility to suite
these needs may be possible, but does not seem quite reasonable.  Therefore, a
WAN configuration utility and corresponding application programmer's interface
is needed for this purpose.

Most of these problems are taken care of by this module.  It's goal is to
provide user with more-or-less standard look and feel for all WAN devices and
assist WAN device driver writer by providing common services, such as:

 o User-level interface via /proc filesystem
 o Centralized configuration
 o Device managenent (setup, shutdown, etc.)
 o Network interface management (dynamic creation/destruction)
 o Protocol encapsulation/decapsulation

To ba able to use Linux WAN Router you will also need a WAN Tools package
available from

	ftp.sangoma.com/pub/linux/wantools-X.Y.Z.tgz

For technical questions and/or comments regarding this product please e-mail
to genek@compuserve.com or dm@sangoma.com.



COPYRIGHT AND LICENSING INFORMATION

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 675 Mass
Ave, Cambridge, MA 02139, USA.



KNOWN BUGS AND LIMITATIONS

/proc user interface is not complete yet.



ACKNOLEGEMENTS

This product is based on the WANPIPE(tm) Multiprotocol WAN Router developed
by Sangoma Technologies Inc. for Linux 1.2.x.  Release of Linux 2.0 in summer
1996 commanded adequate changes to the WANPIPE code to take full advantage of
new Linux features.  Instead of continuing developing proprietory interface
specific to Sangoma WAN cards, we decided to put all hardware-independent code
into a separate module and define two levels of interfaces - one for user-
level applications and another for kernel-level WAN drivers.

Many usefull ideas concerning hardware-independent interface implementation
were given by Mike McLagan <mike.mclagan@linux.org> and his implementation
of the Frame Relay router and drivers for Sangoma cards (dlci/sdla).

Special thanks to all the WANPIPE users who performed field-testing, reported
bugs and made valuable comments and suggestions that help us to improve this
product.



REVISION HISTORY

1.0.0	 December 31, 1996
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 o Initial version.

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