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IPX/SPX
Internetwork Packet Exchange (IPX) was
developed by Novell (based closely on earlier work by Xerox) as a low-level
network transport protocol. It's frequently used in conjunction with the
Sequenced Packet Exchange (SPX) protocol; the two together form the core of a
network stack that's comparable in scope to AppleTalk or NetBEUI. IPX/SPX has
historically been used by the NetWare product, but IPX/SPX packages are
available for DOS, Windows, and other OSs. One of the most popular uses of this
network stack is to support the NetWare Core Protocol (NCP), which is Novell's
file- and printer-sharing tool. Linux also supports these protocols, both in
the kernel (as described in
client and server packages.
IPX/SPX Features and Capabilities
Like TCP/IP and AppleTalk, IPX/SPX supports a
32-bit address, which is usually expressed in hexadecimal, as in 0x23a91002. This
address, however, isn't assigned to a single computer, but to an entire
networkusually a network segment that's isolated from others by routers, or
completely disconnected from the outside world. An IPX/SPX network is also
identified by the underlying hardware's frame type,
which is how the Ethernet frames are built at a very low level; all computers
on a single IPX/SPX network must use the same frame type. To identify
individual computers, IPX/SPX relies on the underlying hardware's addressing
scheme, such as Ethernet's 48-bit (6-byte) addresses.As you might guess from the name and
addressing scheme, IPX/SPX is designed for internetworkingthat is, linking
networks together. This is accomplished via IPX routers, which work much like
TCP/IP routers in broad detail. (In fact, a single system can function as both
a TCP/IP and an IPX router.) A simple network may not require a router, but
IPX/SPX does support the option.IPX/SPX servers use a protocol known as the Service Advertisement Protocol (SAP) to periodically
announce their names and the services they make available, such as shared
directories or printers. Other systems on the local network segment will
"hear" these announcements, and IPX routers should echo them to other
network segments. This design can help make locating the right server easy, but
it can also increase network traffic as the network size increases; with more
servers, there will be more SAP broadcasts consuming network bandwidth.
Using Linux IPX/SPX Software
Like most Linux software, Linux's IPX/SPX
software is largely open source. (Caldera once licensed NetWare from Novell and
made it available for Linux, but Caldera has discontinued this official port of
NetWare. A three-user version is still available from
for Linux include the following: Kernel NCPFS support The Linux kernel includes support for the NCP filesystem in the
Network File Systems submenu of the File Systems menu. This support allows a
Linux computer to mount NetWare file shares. You need the ncpmount program, which usually ships in a package called ncpfs , to accomplish this
task. LinWare This package provides limited NCP server support. At the time of
this writing, however, the current version is 0.95 beta, which was designed for
the 1.3.x kernelsin other words, the software
hasn't been updated since 1996. This might change in the future, though. The
package is housed under the name lwared at
hosted at http://www.compu-art.de/mars_nwe/ , which is largely in German. English documentation is in the
Mars_nwe HOWTO document,
target="_blank">http://www.redhat.com/support/docs/tips/Netware/netwarel . Mars_nwe supports both file and print services. Its primary
configuration file is /etc/nwserv.conf or /etc/nwserv/nwserv.conf , and it can be started by typing nwserv , if it's not
started automatically by a startup script.All of these IPX/SPX packages require you to
have IPX support compiled into your kernel, as described in
distributions also require a separate package, usually called ipxutils ,
which contains utilities for activating and controlling the IPX/SPX network
stack. (Alternatively, some distributions include these tools in the ncpfs package.) If you intend to run a server for NetWare
clients, Mars_nwe configuration is usually not too difficult, because the
default configuration works fairly well. The configuration file is also usually
very well commented, so you can learn how to configure it by reading its
comments. You should pay particular attention to a few details: Section 1 of the file defines the volumes that
are to be shared. In Linux terms, these are directories. The configuration file
that ships with your copy of the server may or may not define volumes that
you'd want to share. Section 7 controls password encryption options. You
may need to enable nonencrypted passwords if your network doesn't have a
regular NetWare bindery servera computer that
handles authentication. Section 13 defines users who are to be allowed
access to the server. You may need to add usernames and passwords to this
section, duplicating the regular Linux username and password configuration. Passwords
are stored in an unencrypted form, which is a potential security flaw. If the
network has a bindery, though, you can remove these entries after starting
Mars_nwe for the first time, so the security risk may not be as bad as it first
appears. Instead of dealing with individual accounts, you can set up Section 15
to do this automatically, but the drawback is that all the accounts will have
the same password.The Mars_nwe package includes the means to
automatically enable IPX support on your network interface. This convenience
doesn't exist in the case of Linux's NetWare client support as implemented in ncpmount ,
however. Before you can use this command, you should enable auto-configuration
with the ipx_configure command. You can then mount a NetWare volume with ncpmount . The
entire procedure might resemble the following: # ipx_configure auto_interface=on auto_primary=on # ncpmount -S NW_SERV -U anne -P p4rtu3a /mnt/nwmount
This sequence enables auto-detection of the
local network number and mounts volumes stored on NW_SERV associated with
the user anne at /mnt/nwmount , using the password p4rtu3a .
